陕北无定河川区多年来没有种植小麦的习惯,1972年以来提倡川水地种植小麦,一些队种植成功而且连年获得平均每亩600斤以上的好收成,并出现了千斤田块。但一般产量不高,扩种很慢,有的增施农家肥底肥,用量达每亩8000—10000斤,并保证了足够的氮素化肥,仍不能改变小麦的低产状态。因而1974年我们对无定河川区土壤作了一次概测,1975、76年我们先后在绥德、米脂川区对小麦生产问题作了调查,并在镇则湾大队进行肥料试验。通过这些工作,我们查明了小麦生长不良的主要原因是土壤中缺乏有效磷。一、无定河川区土壤养分状况和增施 Over the years, there was no habit of planting wheat in Wuchuan County in northern Shaanxi. Since 1972, wheat cultivation has been promoted in Chuan Shui and some plants have been planted successfully. Over the past few years, they have also obtained fine harvests of more than 600 kilograms per mu and a few kilograms of fields. However, the general output is not high, the expansion is very slow, and some increase fertilizer farmer, with an amount of 8000-10000 pounds per acre, and to ensure adequate nitrogen fertilizer, still can not change the low-yielding state of wheat. Therefore, in 1974, we made an overview of the soil in Wuding River. In 1975 and 76, we conducted surveys on the wheat production in Suide and Mizhi-Chuang areas, and conducted fertilizer tests in the Zhenzhai Bay Brigade. Through these efforts, we found that the main reason for the poor growth of wheat is the lack of available phosphorus in the soil. First, the uncertainty of soil nutrients in Hechuan District and the increase