氮肥后移对花铃期水分亏缺棉花产量的补偿效应研究

Compensation effect of nitrogen fertilizer post-shift on water-deficient cotton yield at different stages

花铃期是棉花产量形成最关键的时期,为探究氮肥后移对花铃期水分亏缺棉花产量的补偿效应,以新路早45号为供试材料,采用裂区试验设计,主区设定2个花铃期滴灌量:常规灌溉量2410 m^(3)·hm(−2)(W1)为对照、亏缺灌溉量1668 m^(3)·hm(−2)(W2);副区为3种花铃期施肥比例:N1(花期肥:铃期肥为3:3)、N2(花期肥:铃期肥为2:4)、N3(花期肥:铃期肥为4:2)进行探究。结果表明:(1)相同氮肥条件下,水分亏缺较正常灌溉处理的叶面积指数(LAI)、净光合速率(Pn)显著降低;(2)根据干物质积累Logistic模型,干物质最大积累速率(Vm)出现时间、干物质进入快速积累期时间拐点(t1)均有所提前、干物质快速积累持续时间(Δt)有所延长,生殖器官干物质积累量及占比显著降低;(3)水分亏缺处理的单株铃数、单铃重较正常灌溉平均降低了11.7%,45.6%,籽棉产量平均降低了17.3%,耗水量、氮肥偏生产力平均降低了35.49%、15.97%,水分利用效率平均增加了16.77%。与正常灌溉相比,花铃期水分亏缺条件下,氮肥后移(N2)较N1、N3处理的棉花LAI、Pn都有所增加,且表现为:N2>N1>N3;(4)氮肥后移(N2)处理下的干物质累积量、Δt、Vm表现最优,干物质快速积累期特征值(GT)最为协调,棉花营养生长向生殖生长的转移率最高,为68.25%;(5)与N1和N3处理相比,氮肥后移(N2)处理的棉花单株铃数、单铃重分别增加了10.40%、16.02%和8.41%、11.61%,籽棉产量分别增加了7.32%,13.88%,耗水量、水分利用效率、氮肥偏生产力均表现为:N2>N1>N3。综上所述,氮肥后移通过提高棉花花期LAI及Pn、减缓盛铃后期的LAI和Pn的下降幅度,增加地上部分干物质积累量并提高了生殖器官所占比例,调控产量及其构成要素,以减轻水分胁迫对产量的影响。

The flowering and boll stages are the most critical periods for the formation of cotton.To explore the compensation effect of nitrogen fertilizer backward shift on the yield of water-deficient cotton at the flowering and boll stages,Xinluzao No.45 was used as the test material and a split-plot test design was adopted.The drip irrigation amount in two flowering and boll stages was determined as follows:a conventional irrigation amount of 2410 m^(3)·hm(−2)(W1)was the control and the deficit irrigation amount was 1668 m^(3)·hm(−2)(W2).N1(flowering period fertilizer:boll period fertilizer 3:3),N2(flowering period fertilizer:boll period fertilizer 2:4)and N3(flowering period fertilizer:boll period fertilizer 4:2)was explored.Results showed that under the same nitrogen fertilizer conditions,the leaf area index(LAI)and net photosynthetic rate(Pn)of the water deficit were significantly lower than those of the normal irrigation treatment;was prolonged and the accumulation and proportion of dry matter in reproductive organs decreased significantly;the number and weight of bolls per plant decreased by an average of 11.7%and 45.6%,respectively,compared with normal irrigation;and the yield of seed cotton decreased by an average of 17.3%.The water consumption and partial productivity of nitrogen fertilizer decreased by 35.49%and 15.97%on average,respectively,and water use efficiency increased by an average of 16.77%.Compared with normal irrigation and under a water deficit condition at the flowering and boll stages,the LAI and Pn of cotton treated with nitrogen fertilizer(N2)increased compared with that of N1 and N3 and the expression was N2>N1>N3.The dry matter accumulation,Δt,and Vm performed best under fertilization,GT was the most coordinated,and the transfer rate from vegetative growth to reproductive growth of cotton was the highest at 68.25%.The number of bolls per plant and weight of single bolls increased by 10.40%,16.02%,8.41%,and 11.61%,respectively,and the yield of seed cotton increased by 7.32%and 13.88%,respectively.Water consumption,water use efficiency,and partial nitrogen fertilizer productivity were as follows:N2>N1>N3.In summary,a backward shift in nitrogen fertilizer can increase the LAI and Pn of cotton in the flowering stage,slow down the decline of LAI and Pn in the late boll stage,increase dry matter accumulation in the aerial part and increase the proportion of reproductive organs,and regulate the yield and its components to reduce the impact of water stress.