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Abstract In order to clarify the current situation and main problems in facility vegetable fertilization and guide farmers to fertilize scientifically, an investigation on the yield and fertilization of facility vegetables (tomato, cucumber, eggplant and celery) was carried out in six districts and counties in Shandong Province from 2016 to 2017. The results showed that among the four vegetables, the yield levels of eggplant and celery varied slightly with the coefficient of variation between 7.18% and 27.63%, and the yield levels of tomato and cucumber varied greatly with the coefficient of variation between 33.84% and 65.15%. In terms of fertilization, the differences in N, P2O5 and K2O inputs in cucumber was the largest, and the maximum values of the nutrient inputs were 7.95, 8.54 and 8.77 times of the corresponding minimum values, respectively. The input amounts of N, P2O5 and K2O in tomato, cucumber and eggplant were 1.47-2.68, 3.93-7.50 and 1.09-1.51 times of the corresponding demands, respectively. The N and P2O5 inputs of celery exceeded the demands by 32.00% and 79.00%, respectively, while the K2O input was only 49.00% of the demand. The ratios of N∶P2O5∶K2O input in the total application amount, organic fertilizer, base fertilizer and topdressing chemical fertilizer of facility vegetables were, respectively,1∶0.84∶1.02, 1∶0.84∶0.80, 1∶0.99∶1.05 and 1∶0.77∶1.25. The proportion of P2O5 input was too high, while the proportion of K2O input coming from the organic fertilizer was insufficient. The average proportions of organic fertilizer in N, P2O5 and K2O inputs were 43.96%, 43.72% and 36.99% respectively. The proportions of organic fertilizer in N and P2O5 inputs were reasonable, while that in K2O was lower. In N, P2O5 and K2O inputs of different vegetables, the proportions from organic fertilizer were reasonable in cucumber, higher in eggplant and lower in tomato and celery. The recommendations were presented in this paper that the inputs of N and P2O5 should be reduced, and the inputs of K2O and organic fertilizer should be increased, while farmers should choose fertilizer with low P2O5 and high K2O contents.
Key words Facility vegetable; Fertilization; Investigation; Shandong
Received: February 7, 2020Accepted: April 5, 2020
Supported by Major Science and Technology Innovation Project of Shandong Province (2019JZZY010721); Key Research and Development Project of Shandong Province (2017CXGC0204); Agricultural Scientific and Technological Innovation Project of Shandong Academy of Agricultural Sciences (CXGC2016A06); Agricultural Major Applied Technology Innovation Project of Shandong Province in 2019 (SD2019ZZ006). Ronghui MA (1983-), male, P. R. China, senior agronomist, mainly devoted to research and extension of soil and fertilizer technology.
*Corresponding author. E-mail: jiangli8227@sina.com; sdlblys@163.com.
Affected by traditional planting habits and diet culture, vegetables play an important role in Chinas agricultural production and residents diet structure［1］. Traditional vegetable cultivation is affected by climate, and there are problems of single varieties, seasonality and continuity of consumption. With the development of planting technology, facility cultivation has become an important way of vegetable production in China［2-3］. By regulating the soil environment and climatic environment inside facilities, seasonal and temperature change restrictions on vegetable production are broken, and a microclimate suitable for vegetable growth is created to realize the multiple cropping cultivation and annual supply of vegetables［4］. The amount of fertilizer required during vegetable growth is large, but the output value and benefits are much greater than other crops. Farmers generally believe that applying more fertilizers leads to a higher yield［5］. At present, excessive fertilization (especially nitrogen and phosphorus fertilizers) and unreasonable application are common in vegetables, especially facility vegetables, which not only cause a series of negative effects on vegetable growth, but also lead to nutrient loss and pollution of soil and groundwater environment［1,3,6-7］. Making clear the background values of vegetable field and the main problems in fertilization are the basis for the scientific application of vegetable fertilizers［8］. Huang et al. ［8］ conducted a questionnaire investigation on the amount of nutrient input to the facility vegetables and fertilizer use of the main vegetable varieties under facility cultivation in Chinas main vegetable areas from 2013 to 2015. The results showed that the average amount of chemical fertilizers (N+P2O5+K2O) applied to facility vegetables in Chinas main vegetable areas was 1 354.5 kg/hm2; the amount of chemical fertilizer nutrients applied to facility vegetables in North China and East China was significantly higher than that in Northeast, Central and Southwest China; and the amounts applied to different vegetables ranked as cucumber＞tomato＞chili and eggplant. In addition, there are many reports on the application of vegetable fertilizers in various regions, such as Beijing［9-10］, Tianjin［11-12］, Hebei［11,13］, Shaanxi［6,14-15］, Shanxi［7］ and part of Shandong Province ［2,3,16-19］. Shandong is one of Chinas major vegetable production and export provinces, and one of the "three major vegetable gardens in the world". In the past 10 years, the vegetable planting area has stabilized at about 2 million hectares, accounting for about one-tenth of the national vegetable planting area; and the facility vegetable cultivation area remains at more than 867 000 hectares, about one quarter of the country s facility vegetable cultivation area ［5］. In 2014, the investigation showed that the amount of chemical fertilizers applied to facility tomato in Shandong Province was 903.75 kg/hm2, ranking sixth in the country, and the amount of chemical fertilizers applied to facility cucumber was 1 458.6 kg/hm2, ranking second in the country［1］. In order to clarify the current situation and main problems in facility vegetable fertilization and guide farmers to fertilize scientifically, this study investigated the yield and fertilization of facility vegetables (tomato, cucumber, eggplant and celery) in 6 districts and counties of Shandong Province from 2016 to 2017. This study provides a basis for the reduction of fertilizer application in facility vegetables, so as to achieve high-quality, high-yield, and high-efficiency production of facility vegetables, and zero growth of fertilizers by 2020［1,11］.
Materials and Methods
Investigation area
This investigation selected 6 districts and counties (cities, districts) with a certain planting scale and typical vegetable types, including Shen County, Donge County and Dongchangfu District in Liaocheng City, Shouguang City and Anqiu City in Weifang, and Jiyang District in Jinan City, as the investigation sites for the current situation of vegetable fertilization in facilities.
Investigation methods
Special investigators were arranged to visit the field, answer questions on the spot, fill out the questionnaire, and the vegetable growth period of the investigation is 2016-2017. The investigation content included the types and varieties of vegetables planted, planting/pulling time, yield, fertilization date, fertilizing amount, fertilizer variety and nutrient content, fertilization method, etc. A total of 236 questionnaires were received. The planting methods included rotational and single cropping. The vegetable varieties with a small number of samples were excluded. After sorting, the data of four main vegetables was obtained, and the total number of samples was 151, including 54 parts of tomato (including winter-spring crop, summer-autumn crop, overwintering crop), 46 parts of cucumber (including spring crop, autumn-winter crop, overwintering crop), 34 parts of eggplant (including spring crop and overwintering crop), and 17 parts of celery (autumn crop). The growth period of the winter-spring tomato was from December 2016 to June 2017, the growth period of the summer-autumn crop was from June 2016 to November 2016, and the overwintering crop grew from October 2016 to June 2017. The spring cucumber grew in the period from February 2016 to June 2016, the growth period of the autumn-winter crop was from August 2016 to February 2017, and the overwintering crop grew from September 2016 to June 2017. The growth period of the spring eggplant was from February 2016 to June 2016, and the growth period of the overwintering eggplant was from August 2016 to June 2017. The growth period of autumn celery was from August 2016 to December 2016.
Data analysis
Data processing and statistical analysis were performed with Microsoft Excel 2016 and SPSS 22.0. The nutrient contents of the chemical fertilizers used by farmers involved in the calculation were obtained referring to the packing bags, and the nutrient contents of livestock and poultry manure were obtained referring to the nutrient database of China organic fertilizer (see Table 1 for details). The N, P2O5 and K2O of commercial organic fertilizers were calculated at 2%, 2% and 1% respectively, and the weight of livestock manure was calculated at 400 kg/m3.For vegetable nutrient requirements, we can refer to the data in Table 2.
Results and Analysis
Yields of facility vegetables
The yield levels of the four kinds of facility vegetables in this investigation are shown in Table 3. The yield levels of the same variety in the same crop season were different. The maximum yields of the winter-spring, summer-autumn and overwintering tomato were 4.00, 3.14, and 7.50 times of the corresponding minimums, respectively, and the coefficients of variation ranged from 33.84% to 63.75%. The average yield was the highest in the winter-spring crop, and the lowest in the summer-autumn crop, and the average yield of the winter-spring crop was 1.18 times that of the summer-autumn crop. As to cucumber, the maximum yields of the spring, autumn-winter and overwintering crops were 4.80, 7.33 and 7.00 times of the corresponding minimums, respectively, and the coefficients of variation were in the range of 41.53%-65.15%. The average yield was the highest in the spring crop, and the lowest in the autumn-winter crop, and the average yield of the spring crop was 1.70 times that of the autumn-winter crop. The maximum yields of the spring and overwintering eggplant were 3.00 and 1.25 times of the corresponding minimum values, respectively, and the coefficients of variation ranged from 7.18% to 27.63%. The maximum yield of celery was 1.78 times of the minimum, and the coefficient of variation was 22.51%. The average yield was 84.44 t/hm2. Major nutrient inputs of facility vegetables
N input
Table 4 shows that there were differences in the input of nitrogen nutrient for different types of vegetables. The maximum nitrogen nutrient input of tomato, cucumber, eggplant, and celery was 3.56, 7.95, 3.96 and 4.33 times of the corresponding minimum values, respectively, and the largest difference of nitrogen nutrient input was observed on cucumber. The average values of the nitrogen nutrient input of the four kinds of vegetables were 478.50, 870.58, 1 387.49 and 301.00 kg/hm2, respectively, and the values were 1.47, 1.58, 2.68 and 1.32 times of the demand, respectively.
Ronghui MA et al. Investigation and Research on the Current Status of Fertilization in Facility Vegetables of Shandong Province
The nitrogen nutrient input also varied between different crops of the same type of vegetable. The nitrogen nutrient input of tomato exceeded the demand in different crops, which exceeded the demand by 18.53%, 48.87% and 72.18%, respectively. The maximum input was 4.12, 2.60 and 4.11 times of the minimum input. The maximum nitrogen nutrient input of cucumber in different crops was 3.40, 7.95 and 13.64 times of the corresponding minimum values, respectively. The nitrogen nutrient input in autumn-winter and overwintering crops was 1.84 times and 2.11 times the demand, and the input for the spring crop was insufficient, only accounting for 79.66% of the demand. The nitrogen nutrient input of eggplant in the spring and overwintering crops both exceeded the demand, and was 2.05 and 1.30 times of the demand, respectively, and the maximum input was 4.89 times and 3.53 times of the minimum input, respectively. The maximum amount of nitrogen nutrient input for autumn celery was 4.33 times of the minimum value and 1.32 times of the theoretical demand.
P2O5 input
Different types of vegetables had large differences in P2O5 nutrient input (Table 5). The maximum P2O5 nutrient input of tomato, cucumber, eggplant and celery was 6.33, 8.54, 4.06, and 5.13 times of the corresponding minimums, respectively, and a maximum difference was observed in the P2O5 nutrient input of cucumber, followed by tomato, celery, and eggplant. The average input of P2O5 nutrient of tomato, cucumber, eggplant and celery was 383.77, 795.26, 1 296.69 and 176.16 kg/hm2, respectively, which were 3.93, 4.14, 7.50, and 1.79 times of the demand, respectively.
For different crops of the same type of vegetable, the P2O5 nutrient input also differed. The P2O5 nutrient input of tomato in different crops all exceeded the demand, which was 2.33, 2.81, 3.65 times of the demand respectively, and the maximum input was 6.34, 6.47 and 6.23 times of the minimum input. The maximum P2O5 nutrient input of cucumber in different crops was 5.43, 9.27, and 10.29 times of the corresponding minimums, respectively, and the input exceeded the demand by 1.00, 3.79 and 4.62 times, respectively. The P2O5 nutrient input of eggplants in the spring and overwintering crops exceeded the demand, and was 7.62 times and 5.37 times of the demand, respectively, and the maximum input was 5.83 times and 3.37 times of the minimum input, respectively. The maximum amount of P2O5 nutrient input in autumn celery was 5.13 times of the minimum value and 1.79 times of the theoretical demand. K2O input
Table 6 shows the K2O nutrient consumption statistics of different crops of tomato, cucumber, eggplant and celery. The maximum amounts of K2O nutrient input of tomato, cucumber, eggplant and celery were 4.16, 8.77, 3.56 and 6.42 times of the corresponding minimum values, respectively. The input of K2O nutrient input of cucumber was the largest, followed by celery. The average K2O nutrient input of tomato, cucumber, eggplant and celery was 584.27, 893.38, 1 259.08 and 200.41 kg/hm2, respectively. The K2O nutrient input of cucumber and eggplant exceeded the demand by 20.33% and 50.50%, respectively. The K2O nutrient input of tomato was basically the same as the demand, while the K2O nutrient input of celery was seriously insufficient compared with the demand, accounting for only 48.69% of the demand.
The K2O nutrient input of tomato in different crops was different from the demand. The K2O nutrient input of the overwintering tomato exceeded 23.00% of the demand. The K2O nutrient input of the summer-autumn tomato was basically the same as the demand. The maximum values of nutrient input for the three crops were 5.80, 3.20 and 4.20 times of the corresponding minimum values, respectively. The K2O nutrient input of cucumbers in the autumn-winter and overwintering crops was 1.25 times and 1.78 times of the demand, respectively, while the K2O nutrient input of the spring cucumber only accounted for 58.24% of the demand. The maximum values of the K2O nutrient input for the three crops were 3.58, 9.98 and 12.23 times of the corresponding minimum values. The K2O nutrient input of eggplant in the spring and overwintering crops both exceeded the demand, which exceeded the demand by 80.77% and 19.64%, respectively. The maximum input was 3.79 times and 3.41 times of the minimum input, respectively. The K2O nutrient input of the autumn celery accounted for only 48.69% of the theoretical demand, and the maximum value was 6.42 times of the minimum value.
Nutrient input ratios of facility vegetables
Research and production show that the nutrient requirement of vegetables during the growing period was basically less phosphorus and more potassium, and the absorption ratio of N∶P2O5∶K2O during the whole growing period was about 1∶0.3-0.5∶1.0-1.5 ［10,16,21-22］. The investigation showed that the N∶P2O5∶K2O ratio in the total fertilization amount for facility vegetables was 1∶0.84∶1.02 ; the N∶P2O5∶K2O ratio provided by organic fertilizer was 1∶0.84∶0.80; the N∶P2O5∶K2O ratio of base fertilizer was 1∶0.99∶1.05 ; and the N∶P2O5∶K2O ratio of topdressing fertilizer was 1∶0.77∶1.25. In general, the input of P2O5 is too high, and the input of organic fertilizer is not enough. The N∶P2O5∶K2O ratios in the nutrient inputs for different types of vegetables were different (Table 7). The N∶P2O5∶K2O ratios in the total fertilization amount, organic fertilizer, base fertilizer and topdressing fertilizer for tomato were 1∶0.80∶1.23, 1∶0.82∶0.70 , 1∶0.98∶1.20 and 1∶0.68∶1.64, respectively. The problems were: the proportion of P2O5 input was too high, and the K2O proportion in the organic fertilizer input was insufficient. Especially in the summer-autumn and overwintering crops, the K2O input by the organic fertilizer was seriously insufficient. The N∶ P2O5∶K2O ratios in the total fertilization amount, organic fertilizer, base fertilizer and topdressing fertilizer for cucumber were 1∶0.91∶1.00 , 1∶0.86∶0.90, 1∶1.06∶1.12 and 1∶0.89∶1.07, respectively. The problems were: the proportion of P2O5 input was too high, and the proportions of K2O in the total application amount and organic fertilizer input for the spring-autumn and winter crops and the base fertilizer application for the autumn-winter crop were not enough. The N∶P2O5∶K2O ratios in the total fertilization amount, organic fertilizer, base fertilizer and topdressing fertilizer for cucumber were 1∶0.93∶0.93, 1∶0.93∶0.83, 1∶1.17∶0.97 and 1∶0.81∶1.21, respectively. The problem was that the input of P2O5 accounted for a relatively high proportion, and the input of K2O was insufficient except the top application of chemical fertilizers. For celery, P2O5 accounted for a slightly higher proportion in the nutrient input, while K2O was seriously insufficient.
Sources for facility vegetable nutrient inputs
Studies have shown that the organic fertilizer accounts for 40%-50% of the facility vegetable nutrient input［5］. In this investigation, the organic fertilizer accounted for an average of 43.96% , 43.72% and 36.99% of the three main nutrient inputs of N, P2O5, and K2O, respectively, among which the proportions of N and P2O5 inputs were reasonable, and that of K2O was relatively low. Organic fertilizer accounted for 18.65%-80.19%, 19.23%-79.99% and 8.38%-77.17% of the three main nutrient inputs for different types of vegetables, with large differences. Specifically, the organic fertilizer for tomato accounted for 29.70% , 30.14% and 17.24% of the three main nutrient inputs, respectively; the proportions of the organic fertilizer in the three main nutrient inputs for cucumber were 46.76%, 44.25% and 42.02%, respectively; the proportions for eggplant were 70.82%, 70.29% and 64.33%, respectively; and the proportions for celery were 24.64%, 29.68% and 26.44%, respectively. The proportions of N, P and K nutrients from organic fertilizer were reasonable in cucumber, higher in eggplant and lower in tomato and celery. Discussion and Conclusions
Reasonable fertilization is the prerequisite for ensuring high yield and quality of vegetables. The yield level of vegetables is affected by variety, planting season, growth period and fertilization level, but the yield level of the same variety in the same season is mainly affected by fertilization. From the perspective of yield level alone, among the four kinds of vegetables, the coefficient of variation of the overwintering eggplant was the smallest, which was 7.18% ; the celery and spring eggplant showed the coefficients of variation of 22.51% and 27.63%, respectively; and the overwintering crop of tomato and the autumn-winter and overwintering crops of cucumber had the largest variation, all being greater than 60%.
Vegetables have a short growth period, a high multiple cropping index, and a large fertilizer requirement, especially for nitrogen, phosphorus, and potassium fertilizers. In the past two years, farmers have great differences in the main nutrient input of vegetable fertilization. The maximum inputs of N, P2O5 and K2O nutrients of the four vegetables were 2.60-13.64, 3.37-10.29 and 3.20-12.33 times of the corresponding minimum values, respectively. In contrast, the differences in the inputs of the three nutrients were the largest in cucumber. The N, P2O5 and K2O nutrient inputs of tomato, cucumber and eggplant were 1.47-2.68, 3.93-7.50 and 1.09-1.51 times of the corresponding demands, respectively; and the N and P2O5 nutrient inputs of celery exceeded the corresponding demands by 32.00% and 79.00%, respectively, while the K2O nutrient input was only 48.69% of the demand. Excessive application of nitrogen fertilizer will have a negative impact on the quality of vegetables, especially nitrate exceeding the standard, and it will also cause environmental problems such as soil acidification and groundwater pollution［5,16,22-24］. Excessive phosphate fertilizer can cause iron and zinc deficiency in vegetables and soil［25］. In the future, it is still necessary to adjust the fertilizer use structure, reduce the application of nitrogen and phosphate fertilizers, and increase the input of potassium fertilizers under the condition of ensuring that the yield of vegetables is not reduced［26］.
In terms of nutrient input ratio, the N∶P2O5∶K2O ratios in the total fertilization amount, organic fertilizer, basic fertilizer and topdressing fertilizer of facility vegetables were 1∶0.84∶1.02, 1∶0.84∶0.80 , 1∶0.99∶1.05 and 1∶0.77∶1.25, respectively. The proportion of P2O5 input was too high, while the proportion of K2O input in organic fertilizer was insufficient. The common problem for different crops of different types of facility vegetables was that the proportion of P2O5 input was high, while the proportion of K2O input in organic fertilizer was insufficient.For the too-high proportion of P2O5 input, on the one hand, it was due to the fact that the fertilizer varieties used by farmers were mainly balanced ternary compound fertilizer or water flush fertilizer, and there is also the excessive use of diammonium phosphate with a high phosphorus content. On the other hand, the P2O5 content in the applied compost and commercial organic fertilizer was also high, which might be the reason for the insufficient proportion of K2O in organic fertilizer. In terms of sources of nutrient inputs, the three main nutrient inputs of N, P2O5, and K2O sourced from organic fertilizer accounted for an average of 43.96%, 43.72%, and 36.99%, respectively. According to the basic principles of organic and inorganic combined application, the organic fertilizer accounted for relatively reasonable proportions of N and P2O5 inputs, and the proportion of K2O was relatively low. Among the different types of vegetables, cucumber showed more reasonable proportions of the three main nutrient inputs sourced from the organic fertilizer, and the proportions were higher for eggplant and lower for tomato and celery.
According to the investigation results, there are four main problems in the facility vegetable fertilization at this stage. First, the application of nitrogen, phosphorus and potassium of chemical fertilizers is relatively high. The average application amounts of nitrogen, phosphorus and potassium in the investigated samples were 1.76, 4.55 and 1.15 times of the demands, respectively. All the three kinds of nutrients have the potential for reduced fertilization, especially for phosphorus fertilizers. The second is that there is a large difference in fertilizer application between different farmers. The differences in the nitrogen, phosphorus and potassium nutrient inputs were more than 10 times, indicating that the facility vegetable scientific fertilization technology still needs further research and development. Third, the ratio of N, P, and K nutrients is inappropriate. On the one hand, the total nutrient ratio is incompatible with the absorption rate of vegetables, and on the other hand, it is incompatible with the nutrient requirements of the vegetable growth stage. Fourth, the fertilizer structure needs to be optimized, including the ratio of organic fertilizer to inorganic fertilizer and the ratio of balanced chemical fertilizer to high nitrogen and potassium water soluble fertilizer. In view of the above problems, it is recommended that farmers should reasonably reduce the input of nitrogen and phosphate fertilizers and optimize the amount of potassium fertilizer according to the types of vegetables and yield levels; and it is recommended to choose chemical fertilizer varieties according to vegetable types and growth period, and choose balanced compound fertilizer and appropriate amount of organic fertilizer for base fertilizer, balanced water soluble fertilizer for early topdressing, and low phosphorus and high potassium water soluble fertilizer for middle and later stages. References
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Key words Facility vegetable; Fertilization; Investigation; Shandong
Received: February 7, 2020Accepted: April 5, 2020
Supported by Major Science and Technology Innovation Project of Shandong Province (2019JZZY010721); Key Research and Development Project of Shandong Province (2017CXGC0204); Agricultural Scientific and Technological Innovation Project of Shandong Academy of Agricultural Sciences (CXGC2016A06); Agricultural Major Applied Technology Innovation Project of Shandong Province in 2019 (SD2019ZZ006). Ronghui MA (1983-), male, P. R. China, senior agronomist, mainly devoted to research and extension of soil and fertilizer technology.
*Corresponding author. E-mail: jiangli8227@sina.com; sdlblys@163.com.
Affected by traditional planting habits and diet culture, vegetables play an important role in Chinas agricultural production and residents diet structure［1］. Traditional vegetable cultivation is affected by climate, and there are problems of single varieties, seasonality and continuity of consumption. With the development of planting technology, facility cultivation has become an important way of vegetable production in China［2-3］. By regulating the soil environment and climatic environment inside facilities, seasonal and temperature change restrictions on vegetable production are broken, and a microclimate suitable for vegetable growth is created to realize the multiple cropping cultivation and annual supply of vegetables［4］. The amount of fertilizer required during vegetable growth is large, but the output value and benefits are much greater than other crops. Farmers generally believe that applying more fertilizers leads to a higher yield［5］. At present, excessive fertilization (especially nitrogen and phosphorus fertilizers) and unreasonable application are common in vegetables, especially facility vegetables, which not only cause a series of negative effects on vegetable growth, but also lead to nutrient loss and pollution of soil and groundwater environment［1,3,6-7］. Making clear the background values of vegetable field and the main problems in fertilization are the basis for the scientific application of vegetable fertilizers［8］. Huang et al. ［8］ conducted a questionnaire investigation on the amount of nutrient input to the facility vegetables and fertilizer use of the main vegetable varieties under facility cultivation in Chinas main vegetable areas from 2013 to 2015. The results showed that the average amount of chemical fertilizers (N+P2O5+K2O) applied to facility vegetables in Chinas main vegetable areas was 1 354.5 kg/hm2; the amount of chemical fertilizer nutrients applied to facility vegetables in North China and East China was significantly higher than that in Northeast, Central and Southwest China; and the amounts applied to different vegetables ranked as cucumber＞tomato＞chili and eggplant. In addition, there are many reports on the application of vegetable fertilizers in various regions, such as Beijing［9-10］, Tianjin［11-12］, Hebei［11,13］, Shaanxi［6,14-15］, Shanxi［7］ and part of Shandong Province ［2,3,16-19］. Shandong is one of Chinas major vegetable production and export provinces, and one of the "three major vegetable gardens in the world". In the past 10 years, the vegetable planting area has stabilized at about 2 million hectares, accounting for about one-tenth of the national vegetable planting area; and the facility vegetable cultivation area remains at more than 867 000 hectares, about one quarter of the country s facility vegetable cultivation area ［5］. In 2014, the investigation showed that the amount of chemical fertilizers applied to facility tomato in Shandong Province was 903.75 kg/hm2, ranking sixth in the country, and the amount of chemical fertilizers applied to facility cucumber was 1 458.6 kg/hm2, ranking second in the country［1］. In order to clarify the current situation and main problems in facility vegetable fertilization and guide farmers to fertilize scientifically, this study investigated the yield and fertilization of facility vegetables (tomato, cucumber, eggplant and celery) in 6 districts and counties of Shandong Province from 2016 to 2017. This study provides a basis for the reduction of fertilizer application in facility vegetables, so as to achieve high-quality, high-yield, and high-efficiency production of facility vegetables, and zero growth of fertilizers by 2020［1,11］.
Materials and Methods
Investigation area
This investigation selected 6 districts and counties (cities, districts) with a certain planting scale and typical vegetable types, including Shen County, Donge County and Dongchangfu District in Liaocheng City, Shouguang City and Anqiu City in Weifang, and Jiyang District in Jinan City, as the investigation sites for the current situation of vegetable fertilization in facilities.
Investigation methods
Special investigators were arranged to visit the field, answer questions on the spot, fill out the questionnaire, and the vegetable growth period of the investigation is 2016-2017. The investigation content included the types and varieties of vegetables planted, planting/pulling time, yield, fertilization date, fertilizing amount, fertilizer variety and nutrient content, fertilization method, etc. A total of 236 questionnaires were received. The planting methods included rotational and single cropping. The vegetable varieties with a small number of samples were excluded. After sorting, the data of four main vegetables was obtained, and the total number of samples was 151, including 54 parts of tomato (including winter-spring crop, summer-autumn crop, overwintering crop), 46 parts of cucumber (including spring crop, autumn-winter crop, overwintering crop), 34 parts of eggplant (including spring crop and overwintering crop), and 17 parts of celery (autumn crop). The growth period of the winter-spring tomato was from December 2016 to June 2017, the growth period of the summer-autumn crop was from June 2016 to November 2016, and the overwintering crop grew from October 2016 to June 2017. The spring cucumber grew in the period from February 2016 to June 2016, the growth period of the autumn-winter crop was from August 2016 to February 2017, and the overwintering crop grew from September 2016 to June 2017. The growth period of the spring eggplant was from February 2016 to June 2016, and the growth period of the overwintering eggplant was from August 2016 to June 2017. The growth period of autumn celery was from August 2016 to December 2016.
Data analysis
Data processing and statistical analysis were performed with Microsoft Excel 2016 and SPSS 22.0. The nutrient contents of the chemical fertilizers used by farmers involved in the calculation were obtained referring to the packing bags, and the nutrient contents of livestock and poultry manure were obtained referring to the nutrient database of China organic fertilizer (see Table 1 for details). The N, P2O5 and K2O of commercial organic fertilizers were calculated at 2%, 2% and 1% respectively, and the weight of livestock manure was calculated at 400 kg/m3.For vegetable nutrient requirements, we can refer to the data in Table 2.
Results and Analysis
Yields of facility vegetables
The yield levels of the four kinds of facility vegetables in this investigation are shown in Table 3. The yield levels of the same variety in the same crop season were different. The maximum yields of the winter-spring, summer-autumn and overwintering tomato were 4.00, 3.14, and 7.50 times of the corresponding minimums, respectively, and the coefficients of variation ranged from 33.84% to 63.75%. The average yield was the highest in the winter-spring crop, and the lowest in the summer-autumn crop, and the average yield of the winter-spring crop was 1.18 times that of the summer-autumn crop. As to cucumber, the maximum yields of the spring, autumn-winter and overwintering crops were 4.80, 7.33 and 7.00 times of the corresponding minimums, respectively, and the coefficients of variation were in the range of 41.53%-65.15%. The average yield was the highest in the spring crop, and the lowest in the autumn-winter crop, and the average yield of the spring crop was 1.70 times that of the autumn-winter crop. The maximum yields of the spring and overwintering eggplant were 3.00 and 1.25 times of the corresponding minimum values, respectively, and the coefficients of variation ranged from 7.18% to 27.63%. The maximum yield of celery was 1.78 times of the minimum, and the coefficient of variation was 22.51%. The average yield was 84.44 t/hm2. Major nutrient inputs of facility vegetables
N input
Table 4 shows that there were differences in the input of nitrogen nutrient for different types of vegetables. The maximum nitrogen nutrient input of tomato, cucumber, eggplant, and celery was 3.56, 7.95, 3.96 and 4.33 times of the corresponding minimum values, respectively, and the largest difference of nitrogen nutrient input was observed on cucumber. The average values of the nitrogen nutrient input of the four kinds of vegetables were 478.50, 870.58, 1 387.49 and 301.00 kg/hm2, respectively, and the values were 1.47, 1.58, 2.68 and 1.32 times of the demand, respectively.
Ronghui MA et al. Investigation and Research on the Current Status of Fertilization in Facility Vegetables of Shandong Province
The nitrogen nutrient input also varied between different crops of the same type of vegetable. The nitrogen nutrient input of tomato exceeded the demand in different crops, which exceeded the demand by 18.53%, 48.87% and 72.18%, respectively. The maximum input was 4.12, 2.60 and 4.11 times of the minimum input. The maximum nitrogen nutrient input of cucumber in different crops was 3.40, 7.95 and 13.64 times of the corresponding minimum values, respectively. The nitrogen nutrient input in autumn-winter and overwintering crops was 1.84 times and 2.11 times the demand, and the input for the spring crop was insufficient, only accounting for 79.66% of the demand. The nitrogen nutrient input of eggplant in the spring and overwintering crops both exceeded the demand, and was 2.05 and 1.30 times of the demand, respectively, and the maximum input was 4.89 times and 3.53 times of the minimum input, respectively. The maximum amount of nitrogen nutrient input for autumn celery was 4.33 times of the minimum value and 1.32 times of the theoretical demand.
P2O5 input
Different types of vegetables had large differences in P2O5 nutrient input (Table 5). The maximum P2O5 nutrient input of tomato, cucumber, eggplant and celery was 6.33, 8.54, 4.06, and 5.13 times of the corresponding minimums, respectively, and a maximum difference was observed in the P2O5 nutrient input of cucumber, followed by tomato, celery, and eggplant. The average input of P2O5 nutrient of tomato, cucumber, eggplant and celery was 383.77, 795.26, 1 296.69 and 176.16 kg/hm2, respectively, which were 3.93, 4.14, 7.50, and 1.79 times of the demand, respectively.
For different crops of the same type of vegetable, the P2O5 nutrient input also differed. The P2O5 nutrient input of tomato in different crops all exceeded the demand, which was 2.33, 2.81, 3.65 times of the demand respectively, and the maximum input was 6.34, 6.47 and 6.23 times of the minimum input. The maximum P2O5 nutrient input of cucumber in different crops was 5.43, 9.27, and 10.29 times of the corresponding minimums, respectively, and the input exceeded the demand by 1.00, 3.79 and 4.62 times, respectively. The P2O5 nutrient input of eggplants in the spring and overwintering crops exceeded the demand, and was 7.62 times and 5.37 times of the demand, respectively, and the maximum input was 5.83 times and 3.37 times of the minimum input, respectively. The maximum amount of P2O5 nutrient input in autumn celery was 5.13 times of the minimum value and 1.79 times of the theoretical demand. K2O input
Table 6 shows the K2O nutrient consumption statistics of different crops of tomato, cucumber, eggplant and celery. The maximum amounts of K2O nutrient input of tomato, cucumber, eggplant and celery were 4.16, 8.77, 3.56 and 6.42 times of the corresponding minimum values, respectively. The input of K2O nutrient input of cucumber was the largest, followed by celery. The average K2O nutrient input of tomato, cucumber, eggplant and celery was 584.27, 893.38, 1 259.08 and 200.41 kg/hm2, respectively. The K2O nutrient input of cucumber and eggplant exceeded the demand by 20.33% and 50.50%, respectively. The K2O nutrient input of tomato was basically the same as the demand, while the K2O nutrient input of celery was seriously insufficient compared with the demand, accounting for only 48.69% of the demand.
The K2O nutrient input of tomato in different crops was different from the demand. The K2O nutrient input of the overwintering tomato exceeded 23.00% of the demand. The K2O nutrient input of the summer-autumn tomato was basically the same as the demand. The maximum values of nutrient input for the three crops were 5.80, 3.20 and 4.20 times of the corresponding minimum values, respectively. The K2O nutrient input of cucumbers in the autumn-winter and overwintering crops was 1.25 times and 1.78 times of the demand, respectively, while the K2O nutrient input of the spring cucumber only accounted for 58.24% of the demand. The maximum values of the K2O nutrient input for the three crops were 3.58, 9.98 and 12.23 times of the corresponding minimum values. The K2O nutrient input of eggplant in the spring and overwintering crops both exceeded the demand, which exceeded the demand by 80.77% and 19.64%, respectively. The maximum input was 3.79 times and 3.41 times of the minimum input, respectively. The K2O nutrient input of the autumn celery accounted for only 48.69% of the theoretical demand, and the maximum value was 6.42 times of the minimum value.
Nutrient input ratios of facility vegetables
Research and production show that the nutrient requirement of vegetables during the growing period was basically less phosphorus and more potassium, and the absorption ratio of N∶P2O5∶K2O during the whole growing period was about 1∶0.3-0.5∶1.0-1.5 ［10,16,21-22］. The investigation showed that the N∶P2O5∶K2O ratio in the total fertilization amount for facility vegetables was 1∶0.84∶1.02 ; the N∶P2O5∶K2O ratio provided by organic fertilizer was 1∶0.84∶0.80; the N∶P2O5∶K2O ratio of base fertilizer was 1∶0.99∶1.05 ; and the N∶P2O5∶K2O ratio of topdressing fertilizer was 1∶0.77∶1.25. In general, the input of P2O5 is too high, and the input of organic fertilizer is not enough. The N∶P2O5∶K2O ratios in the nutrient inputs for different types of vegetables were different (Table 7). The N∶P2O5∶K2O ratios in the total fertilization amount, organic fertilizer, base fertilizer and topdressing fertilizer for tomato were 1∶0.80∶1.23, 1∶0.82∶0.70 , 1∶0.98∶1.20 and 1∶0.68∶1.64, respectively. The problems were: the proportion of P2O5 input was too high, and the K2O proportion in the organic fertilizer input was insufficient. Especially in the summer-autumn and overwintering crops, the K2O input by the organic fertilizer was seriously insufficient. The N∶ P2O5∶K2O ratios in the total fertilization amount, organic fertilizer, base fertilizer and topdressing fertilizer for cucumber were 1∶0.91∶1.00 , 1∶0.86∶0.90, 1∶1.06∶1.12 and 1∶0.89∶1.07, respectively. The problems were: the proportion of P2O5 input was too high, and the proportions of K2O in the total application amount and organic fertilizer input for the spring-autumn and winter crops and the base fertilizer application for the autumn-winter crop were not enough. The N∶P2O5∶K2O ratios in the total fertilization amount, organic fertilizer, base fertilizer and topdressing fertilizer for cucumber were 1∶0.93∶0.93, 1∶0.93∶0.83, 1∶1.17∶0.97 and 1∶0.81∶1.21, respectively. The problem was that the input of P2O5 accounted for a relatively high proportion, and the input of K2O was insufficient except the top application of chemical fertilizers. For celery, P2O5 accounted for a slightly higher proportion in the nutrient input, while K2O was seriously insufficient.
Sources for facility vegetable nutrient inputs
Studies have shown that the organic fertilizer accounts for 40%-50% of the facility vegetable nutrient input［5］. In this investigation, the organic fertilizer accounted for an average of 43.96% , 43.72% and 36.99% of the three main nutrient inputs of N, P2O5, and K2O, respectively, among which the proportions of N and P2O5 inputs were reasonable, and that of K2O was relatively low. Organic fertilizer accounted for 18.65%-80.19%, 19.23%-79.99% and 8.38%-77.17% of the three main nutrient inputs for different types of vegetables, with large differences. Specifically, the organic fertilizer for tomato accounted for 29.70% , 30.14% and 17.24% of the three main nutrient inputs, respectively; the proportions of the organic fertilizer in the three main nutrient inputs for cucumber were 46.76%, 44.25% and 42.02%, respectively; the proportions for eggplant were 70.82%, 70.29% and 64.33%, respectively; and the proportions for celery were 24.64%, 29.68% and 26.44%, respectively. The proportions of N, P and K nutrients from organic fertilizer were reasonable in cucumber, higher in eggplant and lower in tomato and celery. Discussion and Conclusions
Reasonable fertilization is the prerequisite for ensuring high yield and quality of vegetables. The yield level of vegetables is affected by variety, planting season, growth period and fertilization level, but the yield level of the same variety in the same season is mainly affected by fertilization. From the perspective of yield level alone, among the four kinds of vegetables, the coefficient of variation of the overwintering eggplant was the smallest, which was 7.18% ; the celery and spring eggplant showed the coefficients of variation of 22.51% and 27.63%, respectively; and the overwintering crop of tomato and the autumn-winter and overwintering crops of cucumber had the largest variation, all being greater than 60%.
Vegetables have a short growth period, a high multiple cropping index, and a large fertilizer requirement, especially for nitrogen, phosphorus, and potassium fertilizers. In the past two years, farmers have great differences in the main nutrient input of vegetable fertilization. The maximum inputs of N, P2O5 and K2O nutrients of the four vegetables were 2.60-13.64, 3.37-10.29 and 3.20-12.33 times of the corresponding minimum values, respectively. In contrast, the differences in the inputs of the three nutrients were the largest in cucumber. The N, P2O5 and K2O nutrient inputs of tomato, cucumber and eggplant were 1.47-2.68, 3.93-7.50 and 1.09-1.51 times of the corresponding demands, respectively; and the N and P2O5 nutrient inputs of celery exceeded the corresponding demands by 32.00% and 79.00%, respectively, while the K2O nutrient input was only 48.69% of the demand. Excessive application of nitrogen fertilizer will have a negative impact on the quality of vegetables, especially nitrate exceeding the standard, and it will also cause environmental problems such as soil acidification and groundwater pollution［5,16,22-24］. Excessive phosphate fertilizer can cause iron and zinc deficiency in vegetables and soil［25］. In the future, it is still necessary to adjust the fertilizer use structure, reduce the application of nitrogen and phosphate fertilizers, and increase the input of potassium fertilizers under the condition of ensuring that the yield of vegetables is not reduced［26］.
In terms of nutrient input ratio, the N∶P2O5∶K2O ratios in the total fertilization amount, organic fertilizer, basic fertilizer and topdressing fertilizer of facility vegetables were 1∶0.84∶1.02, 1∶0.84∶0.80 , 1∶0.99∶1.05 and 1∶0.77∶1.25, respectively. The proportion of P2O5 input was too high, while the proportion of K2O input in organic fertilizer was insufficient. The common problem for different crops of different types of facility vegetables was that the proportion of P2O5 input was high, while the proportion of K2O input in organic fertilizer was insufficient.For the too-high proportion of P2O5 input, on the one hand, it was due to the fact that the fertilizer varieties used by farmers were mainly balanced ternary compound fertilizer or water flush fertilizer, and there is also the excessive use of diammonium phosphate with a high phosphorus content. On the other hand, the P2O5 content in the applied compost and commercial organic fertilizer was also high, which might be the reason for the insufficient proportion of K2O in organic fertilizer. In terms of sources of nutrient inputs, the three main nutrient inputs of N, P2O5, and K2O sourced from organic fertilizer accounted for an average of 43.96%, 43.72%, and 36.99%, respectively. According to the basic principles of organic and inorganic combined application, the organic fertilizer accounted for relatively reasonable proportions of N and P2O5 inputs, and the proportion of K2O was relatively low. Among the different types of vegetables, cucumber showed more reasonable proportions of the three main nutrient inputs sourced from the organic fertilizer, and the proportions were higher for eggplant and lower for tomato and celery.
According to the investigation results, there are four main problems in the facility vegetable fertilization at this stage. First, the application of nitrogen, phosphorus and potassium of chemical fertilizers is relatively high. The average application amounts of nitrogen, phosphorus and potassium in the investigated samples were 1.76, 4.55 and 1.15 times of the demands, respectively. All the three kinds of nutrients have the potential for reduced fertilization, especially for phosphorus fertilizers. The second is that there is a large difference in fertilizer application between different farmers. The differences in the nitrogen, phosphorus and potassium nutrient inputs were more than 10 times, indicating that the facility vegetable scientific fertilization technology still needs further research and development. Third, the ratio of N, P, and K nutrients is inappropriate. On the one hand, the total nutrient ratio is incompatible with the absorption rate of vegetables, and on the other hand, it is incompatible with the nutrient requirements of the vegetable growth stage. Fourth, the fertilizer structure needs to be optimized, including the ratio of organic fertilizer to inorganic fertilizer and the ratio of balanced chemical fertilizer to high nitrogen and potassium water soluble fertilizer. In view of the above problems, it is recommended that farmers should reasonably reduce the input of nitrogen and phosphate fertilizers and optimize the amount of potassium fertilizer according to the types of vegetables and yield levels; and it is recommended to choose chemical fertilizer varieties according to vegetable types and growth period, and choose balanced compound fertilizer and appropriate amount of organic fertilizer for base fertilizer, balanced water soluble fertilizer for early topdressing, and low phosphorus and high potassium water soluble fertilizer for middle and later stages. References
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