| Crop straw retention has been adopted as a strategy in improving soil productivity,and grain yield.Huaibei plain of Anhui province is an important food supply area in China,in this area a winter wheat/summer maize rotation pattern is dominantly adopted over the last decade and presumably incoming years.The typical soil type in this region is lime concretion black soil,which has high soil compaction,low soil organic carbon and poor soil fertility,which is one of the important reasons for low and instability grain yield.Therefore a long-term field experiment of straw return was set up in Huaibei plain,Anhui Province form 2008.The objectives of this study are to investigate the effect of long-term straw return on soil fertility and grain yield from 2013 to 2015.At the same time we conducted a 3-year field experiment to assess the effects of straw return on maize production as affected by sowing water and base/topdressing nitrogen ratios.The main contents and results are as follows:（1）With fertiliser use,long-term straw return had no significantly effect on soil pH at 0-20cm soil layer.Both wheat and maize straw full return（W1M1F1 treatment）significantly reduced soil bulk density by 4.67-6.71%,significantly increased soil porosity and soil water storage by 6.01-8.00%and 3.79-4.64%respectively,at 0-20 cm soil layer（p<0.05）.At the same time soil organic matter,total N,hydrolysable N,available P,and available K was been significantly increased by 15.54-41.58%,7.55-24.38%,10.86-36.29%,13.25-37.61%and16.92-47.42%,respectively.The effects of full straw return of both crop seasons with fertiliser use on soil was obvious than straw return of single crop season（W0M1F1 and W1M0F1 treatment）,and significant than full straw return of both crop seasons without fertiliser use.（2）Without fertiliser use,regardless of straw return,maize grain yield(2728.89-5179.47kg ha-1)was rather lower compared to the treatments with fertiliser use(8856.65-10257.71kg ha-1).Although grain yield was significantly improved by both wheat and maize straw return in 2014-2015,it couldn’t compensate the loss due to no fertiliser application.This indicated that straw return practice should be combined with appropriate fertiliser use in ensuring maize productivity.（3）With fertiliser use,long-term both wheat and maize full straw return significantly increased maize grain yield by 9.78-11.27%across 2013-2015,however in W1M0F1 or W0M1F1 treatment,only one out of three seasons was significantly improved.Long-term full straw return had no significantly effect on maize ear number and thousand-kernel weight,however,it can increased maize ear length,kernel per row and kernel number,and had a tendency to reduced ear tip abortion.W1M1F1 significantly increased kernel number by 12.64%,8.84%and 7.34%across 2013-2015,respectively,but significantly decreased coefficient of variation of ear length,kernel per row,kernel number and kernel weight by1.76-5.15%,4.88-8.39%,2.66-10.51%and 5.21-7.94%,respectively.Therefore,with fertiliser use,long-term full straw return increased maize ear length and kernel per row,increased kernel number,and increased maize yield.Long-term full straw return also improved the uniformity of ear characters,improved the stability of the maize grain yield.（4）Long-term full straw return increased maize dry matter accumulation.Both wheat and maize straw return combination with fertilser increased maize stage growth rate,which significantly increased maize stage（from big flare to anthesis）dry matter accumulation and colony growth rate by 7.70-13.59%and 25.20-31.33%respectively,and significantly increased maize dry matter accumulation at anthesis and maturity stage by 23.16-24.02%and 13.53-19.90%respectively.With fertiliser use,long-term full straw return significantly decreased total translocation proportion,increased assimilates accumulation after anthesis to kernel.Besides,with fertiliser use long-term full straw return decreased sheath and stem of under-ear layer translocation proportion,thus improved the maize lodging resistance.（5）With use of fertiliser,long-term straw return increased maize leaf NR and rubisco activity,SPAD,leaf area index,the chlorophyll density and the net photosynthetic rates（Pn）.Long-term straw return companion with fertiliser also postponed senescence of leaf of ear layer and above-ear layer,maintaining high SPAD in later growth period.So with use of fertiliser,long-term straw return enhanced maize carbon,nitrogen metabolism,and increased Pn.The effects of full straw return of both crop seasons with fertiliser use on physiological property and photosynthetic characters of maize was obvious than straw return of single crop season.（6）Under straw incorporation,sowing water accelerated seedling emergence by 2-7 days,promoted maize seedling growth,increased maize SPAD,leaf area and chlorophyll density.So sowing water increased grain yield by 5.75%（2013）,4.73%（2014）and 5.90%（2015）,and water use efficiency by 1.69%（2014）and 3.80%（2015）compared to the treatment without sowing water.（7）Under straw incorporation,postponing nitrogen application increased grain yield by9.00-10.12%via greater kernel number,and increased nitrogen partial factor productivity in both years.The improved grain yield by splitting nitrogen was due to greater canopy photosynthetic capacity with higher leaf area index,leaf chlorophyll content and net photosynthesis rate.It was found that the optimal ratio of basal:topdressing nitrogen depended on whether sowing irrigation was used.Without sowing water,5:5 basal/topdressing nitrogen significantly increased maize ear length and kernel per row,which further significantly increased maize kernel number,grain yield and nitrogen use efficiency.With sowing water,postponing nitrogen application reduced maize ear tip abortion,significantly increased maize ear length,row（2013）,kernel per row（2014-2015）,which further significantly increased maize kernel number.And 3:7 basal/topdressing nitrogen significantly increased maize grain yield and nitrogen use efficiency.In addition,postponing nitrogen application improved the uniformity of ear characters,improved the stability of the maize grain yield.Therefore,long-term straw retention was able to reduced soil bulk density,increased soil water storage,soil nutrient content at 0-20 cm soil layer,thus improved the soil productivity,promoted maize growth,increased maize productivity in lime concretion black soil area of Huaibei plain,Anhui.Full straw return of both wheat and maize was more beneficial in boosting grain yield compared to a single crop,and that use of chemical fertiliser was necessary in straw return practise.Under straw retention,the combination of sowing water and splitting nitrogen to the big flare stage could increase not only maize grain yield,but also resource-use efficiency. |
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