半干旱地区地膜覆盖和施氮对春小麦生育进程和干物质积累的影响

以春小麦为供试作物 ,在年降水量 4 15 mm的黄土高原中部黄绵土上进行了大田试验 ,研究了地膜覆盖 (设不覆膜、播种后覆膜 30 d、覆膜 6 0 d和全程覆膜 4个水平 )、施氮 (设不施氮和每公顷施氮 75 kg2个水平 )和底墒 (设低、高 2个底墒水平 )对小麦生育进程和干物质积累的影响。结果表明 ,与不覆膜相比 ,覆膜后春小麦出苗时间提前 1～ 9d(大部分提前 3～ 6 d) ;在作物生长中期 ,适时揭膜能够显著增加有效分蘖数 ,提高后期结实穗数 ,延长成熟期 ,有利于作物形成大粒 ,提高千粒重。全程覆膜虽然也改变了作物生育进程 ,但对后期生长不利 ,导致灌浆期缩短 ,无效分蘖增加 ,千粒重下降。生长前期覆膜 ,不仅能显著增加作物生长前期地上部分干物质的迅速积累 ,而且对中、后期干物质进一步累积和产量形成也具有重要作用。2种底墒处理一致表明 ,随着小麦生育进程的推进 ,不仅不同覆膜处理单位面积干物质累积量的差异缩小 ,而且与不覆膜处理之间的差异降低 ,表明后期覆膜在春小麦同化产物累积上并没有实际意义。覆膜后 ,地上部分生物量 ,特别是茎部生长旺盛 ,重量显著增加 ,但随着生育进程的推进 ,根冠比下降 ,显然地膜覆盖抑制了较多同化产物流向根部。综合 2年试验结果 ,春小麦生长前期覆膜 ,有利于根冠比在作物?

Effects of plastic film mulching and nitrogen fertilization on spring wheat growth progress and dry matter accumulation

A field experiment was carried out on cultivated loessial soil in semiarid area with 415 mm precipitation and spring wheat ( Triticum aestivum ) used as an indicating crop to study the effects of plastic film mulching period(including no mulching,mulching for 30 days,mulching for 60 days,after sowing and mulching for whole growing period),nitrogen fertilizer application (including no nitrogen application and nitrogen application 75 kg/hm 2 ) and soil water storage amount in soil profile before sowing (including low and high water storage amount)on the spring wheat growth progress and dry matter accumulation.The results showed that plastic film mulching could make the seedling 1-9 days earlier than no film mulching treatment (mostly 3-6 days earlier).Uncover film mulching in a eligible time can improve wheat growth process remarkably and benefit to last maturity stage.Earlier seedling had a significantly positive effect on the whole spring wheat growth process,it increased valid number of tillering and post filling for grain;the delayed maturity was beneficial for formation of big grain and increasing weight per 1000 kernel.Film mulching in all growing period might change wheat growth process but it also did harm to post growing period and decrease the kernel filling period,1000 kernel weight;increase invalid number of tilling.Film mulching at the earlier growing period could not only increase shoot matter accumulation remarkably but also had a vigorous effect on further dry matter accumulation and formation of yield in mid growing and post growing stages.The shoot biomass yield in the three film mulching treatments was the biggest at 60 days after sowing when the soil water storage amount was higher,and after this period,the shoot biomass yield appeared to decrease tendency.The shoot biomass yield was the biggest at 90 days after sowing of non mulching treatments in both low and high soil water storage amount before sowing,it showed that it remained maintain a high producing ability from 60 to 90 days for non-mulching treatments.As for unit area dry matter accumulation at 90 days after sowing,in high soil water storage amount condition before sowing,the biomass yield was the biggest in the treatment of mulching for 60 days,and in low soil water storage amount condition,the biomass yield was the biggest in the treatment of mulching for 30 days,it showed that high soil water storage water before sowing could delay mulching process in some extent.On the other hand,the two soil water storage amount treatments indicated simultaneously that difference among unit area dry matter accumulation in various treatments decreased as wheat growth process progress,it revealed that it did bad for photosynthate accumulation if film mulching continued in later wheat growing stage.View at the distribution of the biomass yield underground,the weight of the biomass yield,especially that of stem increased remarkably after mulching,resulted in decreasing of R/S as the wheat growth process progress.Obviously it hampered photosynthate flowing to the root after mulching,compared with non mulching treatment,R/S was the highest in earlier growing period,decreased remarkably in later growing period,it was the lowest at 90 days after sowing and stabilized after that.Generalized the result in two years,film mulching in earlier growing period of spring wheat was beneficial to maintain a high R/S ratio in later growing period;film mulching in whole growth period was detrimental to maintain a high R/S ratio.On the other hand,the negative effect of film mulching in whole growth period was to make much photoynthate flowing to stems and leaves,and reduce the harvest index.