【摘要】 <正> 近多年许多试验研究认为,渭北旱原土壤严重缺磷,施磷增产效果明显。结果一些地方出现不分土壤,不分作物种类,年年施磷肥,料料施磷肥的现象。鉴于我国化肥不足,磷矿资源短缺,为了合理地施用化肥,应当根据作物的需要,并摸清土壤是缺氮还是缺磷,然后有针对性地施用化肥,以充分发挥化肥应有的增产作用。为此,1981年以更多还原

【Abstract】 In the vast arid highland of weiboi area with an annual precipitation above 500 mm, the poor fertility of farmland appears to be the reason for low yield in farm crops, and so applying more chemical fertilizers is the essential measure to increase the yield of farm crops.It was considered that in weibei rainfed highland there is a serious lackness of phosphorus, application of this hind of fertilizer may help the P-liking crops such as pea, rape and wheat to raise their yields considerably.The results obtained from pot-planting experiments, conducted in the poor soil (sampling to the depth of 0—33cm) of the Luojiawa Experimental Station in Chengcheng Gounty show that for the pea crop there was no increase of yield with a single application of nitrogen fertilizer, but application of phosphorus could make the crop increase its yield, and that the results obtained with application of N and P fertilizers in good proportion are the same as a single application of P fertilizer. Obviously, for the pea crop, it is lack of P, and not N,and therefore,a single application of P is needed without combination of N and P. However,for rape a single application of P fertilizer can not help to raise its yield, and only applying these two fertilizers in good proportion may lead to an increase in yield. From here it can be seen that for rape the soil is lacking both in N and P, and it is necessary to apply the two fertilizers in combination. A single application of P cannot raise the yield of wheat, but N can do. with the amount of N increased, there will be a lackness of P felt, so it is necessary to apply N and P in combination in order to get further increases in yield.Is it a problem caused by lack of P or one caused by lack of N in the poor farm land in weibei rainfed areas? The results obtained from our experiment indicate that the answer should be decided by the crop types, yield index, conditions of soil and fertilization in previous cropping. According to the principles mentioned above it might be necessary to make a deeper research on the previous conclussion that the problem was one caused by a serious lack of P in this area.更多还原