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水分是作物生长发育的主要生态因素,也是农业生产中存在的主要问题,全世界近210亿亩耕地中,有灌溉条件的仅占10％,其余皆为雨养农业。在雨养农田中,约有90亿亩属干旱和半干旱地区,年降雨量在500毫米以下,这个地区的作物生长总是受到水份供应不足的制约。甘肃省定西地区属于我国西北黄土高原丘陵沟壑区,年降雨量在250—500毫米之间,又多集中在七、八、九三个月。绝大部分山、川旱地无灌溉条件,主要夏粮作物春小麦生长发育
Water is the main ecological factor of crop growth and development. It is also a major problem in agricultural production. Of the nearly 21 billion mu of cultivated land in the world, only 10% have irrigated land and the rest are rainfed agriculture. About 9 billion acres of rain-fed farmland are arid and semi-arid areas with an annual rainfall of less than 500 millimeters, and crop growth in this area is always constrained by inadequate water supplies. The Dingxi area in Gansu Province belongs to the hilly and gully regions of the Loess Plateau in Northwest China. The annual rainfall is between 250-500 mm and is mostly concentrated in seven, eight and ninety-three months. Most of the mountains, dry conditions in Sichuan irrigation, the main summer crop spring wheat growth