| Rice-wheat rotation is one of the main rice cultivation modes in the middle and lower reaches of the Yangtze River.With the intensification of water shortages and the increase in drought frequency,the advantages of upland rice are becoming increasingly apparent.However,the impact of upland rice on crops,soil,resource utilization and economic benefits during the rice season is not systematically studied.To this end,this experiment Conventional irrigation and upland treatments were set up during the rice season using three rice varieties:indica hybrid rice Hanyou73(HY73),indica inbred rice Huanghuazhan(HHZ),japonica hybrid rice Yongyou4949(YY4949)and one wheat variety(Zhengmai 9023)as experimental materials to systematically analyze the effects of upland treatment on different types of rice and wheat growth and development,yield and quality,soil properties,annual resource utilization efficiency and economic benefits.The following preliminary research results were obtained:(1)Plant height,tiller number,leaf area and leaf water potential of different types of rice in some key growth stages were studied by dry farming.The largest reduction in chlorophyll content occurred during the tillering stage,with an average reduction of20.5%for indica varieties and 13.6%for japonica varieties,which was relatively small;the largest reduction in leaf water potential occurred during the heading and flowering stage,with an average reduction of 34.1%for indica varieties and 28.4%for japonica varieties.The plant height,tiller number,leaf water potential and photosynthetic pigment content of indica rice varieties decreased significantly after dry cultivation,while the leaf area of indica-japonica hybrid rice decreased significantly.The degree of damage to the protective enzyme system of rice under upland treatment was higher in indica than japonica and higher in inbred than hybrid.Under upland treatment,both yield and processing quality of rice showed a downward trend.The yield of HY73 decreased from 7t/hm~2to 5 t/hm~2;HHZ decreased from 6 t/hm~2to 4.2 t/hm~2;YY4949 decreased from 7.3t/hm~2to 5.1 t/hm~2;all reached a significant level.The milled rice rate and brown rice rate of indica-japonica hybrid rice under conventional flooding irrigation were higher than those of indica rice.After dry farming,the milled rice rate and brown rice rate of indica rice decreased by 3.4%on average,and the average decreased by 0.7%on indica-japonica hybrid rice.Amylose content of indica hybrid rice increased while that of conventional indica rice and indica-japonica hybrid rice decreased after dry farming.(2)Upland treatment during the rice season significantly affected soil properties and microbial communities.In upland treatment soil,nitrate nitrogen content and p H exhibited an upward trend with nitrate nitrogen content showing the maximum difference during mid-growth period increasing from 3.8 mg/kg to 9.4 mg/kg in 0-20 cm soil layer while from 4.6 mg/kg to 5.9 mg/kg in 20-40 cm soil layer;soil p H showed the maximum difference at maturity increasing from 5.6 to 6.0 in 0-20 cm soil layer.In addition,total reducing substances,active reducing substances,ferrous iron and ferrous manganese content all showed a decreasing trend with reductions respectively being 19%40%52%and 48%.By performing PCR amplification on soil samples followed by Illumina Miseq sequencing,it was found that after upland treatment during the rice season,the types and proportions of dominant bacterial groups changed in different depths of plowed soil.In the 20-40 cm soil layer,the dominant bacterial groups and their proportions changed significantly with Acidobacteriota having the highest relative abundance in conventional irrigation treatment accounting for 19.46%while Chloroflexi had the highest relative abundance in upland treatment accounting for 20.70%.(3)Post-season wheat after upland treatment during the rice season has a large biomass which is conducive to growth and development as well as yield and quality improvement.Under upland treatment,post-season wheat not only had significantly greater plant height,tillering number,leaf area,second leaf length from bottom up,leaf width,spikelet number and spike length than irrigated control but also had obvious advantages in accumulation of stem,leaf and spike dry matter which may be related to higher root activity and root absorption area after upland treatment.In terms of yield,post-season wheat after upland treatment during the rice season had a yield of 4.49 t/hm2which was 7.7%higher than irrigated control.As for grain quality,post-season wheat after upland treatment had higher grain protein content and gluten content than irrigated control.(4)After upland treatment during the rice season,water production efficiency during rice season,wheat season and annual system all significantly increased with annual water use efficiency increasing from 54%to 137%.But other resource use efficiencies showed opposite performance between two crops.Although nitrogen fertilizer partial productivity light energy utilization efficiency and accumulated temperature utilization efficiency all significantly increased during wheat season,due to yield reduction of rice caused by upland treatment nitrogen fertilizer partial productivity light energy utilization efficiency and accumulated temperature utilization efficiency all decreased during rice season and annually.Upland treatment during rice season reduced water,electricity and labor expenditure,thus after upland treatment economic benefits of rice season,wheat season and annual system all increased,with annual economic benefits of HY73,HHZ,YY4949 respectively increasing by 20.7%33.1%and 8.4%in rice-wheat rotation.To sum up,soil physical and chemical properties and microorganisms changed after dry farming in rice season.The yield and quality of different types of rice decreased,among which the yield of HY73 and YY4949 decreased slightly,and the rice quality of YY4949 could be improved under dry farming;The wheat in the later season of dry farming in rice season has higher yield and better quality In addition,the annual water use efficiency and economic benefits of rice-wheat rotation system were significantly improved by dry farming The results of this experiment can provide theoretical basis for dry cultivation of rice under rice-wheat rotation. |
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