圈粪、炕土、堆肥等以土为主体的农家肥通常统称为土粪,其养分含量一般按全氮计,但在实际应用中,土粪施量大,虽氮素量多,而肥效甚差。对其肥效差的原因往往解释为其氮素利用率很低,这种解释与实际不符。如果土粪按全氮计,等于把垫土中的全氮量均与视作肥料氮素,而完全忽视了土粪中垫土和田间土壤含氮量之间的平衡关系。据观察,凡亩施有2～2.5万斤土粪的水稻、小麦,如按土粪全氮计,其施氮量总是要比单施其它无土肥料(油饼、绿肥、化肥)高出近20斤,方能达到长势和产量相近的水平。此值已接近于水稻正常施氮量或相当于小麦正常施量的1/2以上,因此在研 Circle manure, kang soil, compost and other soil-based farmyard manure are generally collectively referred to as soil manure, and its nutrient content is generally based on total nitrogen, but in practical applications, soil manure is large, although the amount of nitrogen, and fertilizer Very bad. The reasons for its poor efficiency are often explained as low nitrogen utilization rate, this explanation does not match with reality. If the soil manure by total nitrogen is equal to the amount of total nitrogen in the soil as fertilizer nitrogen, completely ignore the balance between soil manure and soil nitrogen content in the soil. It has been observed that rice and wheat with 2-25,000 kg soil manure per mu are always higher than other soilless fertilizers (oil cakes, green manures and chemical fertilizers) Nearly 20 pounds, in order to reach the same level of growth and output. This value is close to normal nitrogen application rate of rice or equivalent to more than 1/2 of the normal amount of wheat,