花碱土地区长期施用化肥对土壤的影响和增产效应

Effects of Long-term Application of Chemical Fertilizers on Soil and Crop Yields in Xuhuai Patch-alkali Soil District

通过对黄泛冲积物发育的盐碱化潮土的长期定位试验和土壤、植物分析,研究了小麦-夏玉米轮作制下的产量演变;有机肥和化肥的肥效;土壤养分的变化和平衡,以及土壤盐分及其组成的变化。结果表明:年平均产量 NPK>NP>NK>PK;单施化肥的单位养分增产量 P_2O_5>N>N_2O;配施有机肥时,N>K_2O>P_2O_5。化肥生产率玉米大于小麦,单施化肥大于配施有机肥。每年每公顷施 N375kg,P_2O_5187.5kg,K_2O 225kg 可维持氮磷钾养分的平衡。土壤中 Mg、B、Cu、Mn明显减少,单施有机肥不能维持土壤硫素平衡,土壤全盐量、pH 值、离子组成等变化不大。但仍应加强排水,提高土壤肥力,防止可溶性盐在土壤表层积累。

A long-term fertilization experiment has been carried out on desalinized and dealka- lized fluvo-aquic soil in Suining County,Jiangsu Province since 1986 with a background of winter wheat-summer maize rotation.The treatments were divided into two groups,applying yard manure (299 kg N,224 kg P_2O_5,372 kg K_2O/hm^2/year)and not applying,each of which consisted of 5 subtreatments with different chemical ferililizers:zero fertilizer;applying 187.5 kg P_2O_5 and 187.5kg K_2O/hm^2/year(denoted by PK);applying 375 kg N and 187.5kg K_2O/hm^2/year(NK); applying 375kg N and 187.5kg P_2O_5/hm^2/year(NP);applying 375kg N,187.5 kg P_2O_5 and 187.5kg K_2O/hm^2/year(NPK).The results obtained from 1986 to 1993 are as follows:①Whether applying yard manure or not,the crop yields in both groups of treatments were arrranged in the same order:NPK>NP>NK>PK.②With only chemical fertilizers applied,the order of increased yields brought about by each kilogram of chemical nutrient was P_2O_5>N>K_2O.However,if yard manures was incorperated,the order shifted to N>K_2O>P_2O_5.③Path analysis showed that the main factors affecting crop yields were the amount of total nitrogen,slowly available potassium and organic matter in the soil.④The balance of N,P and K in soil could be kept by applying 375 kg N,187.5kg P_2O_5 and 225kg K_2O per hm^2 annually.⑤After planting crops for ten seasons, available Mg,B,Cu and Mn were notably reduced in the soil.Available S was greatly reduced in the soil of blank check and in that only applied with yard manure.⑥After planting crops for seven years,a very little increase in total salt content was observed in soil;ion population changed slightly;the pH value generally decreased and was less than 8.5 in the plowed layer.Therefore,secondary salinization and alkalinization are unlikely to occur in the districts investigated at the present level of fertilizer application.