| This study was carried out from 2014 to 2016 on Experimental Farm of Key Laboratory of Crop Genetics and Physiology of Jiangsu Province in Yangzhou Univeristy.The aim of this paper was to investigate the effects of rice straw returning mode,sowing depth,nutrient aplication ratio on wheat production of Yangfumai 4,and also to explore the appropriate high-yield cultivation methods of Yangfumai 4 under different conditions of rice staw returning mode and amount.The study is of importance for providing a theoretical and technological support for achieving high yield and grain quality under straw returning.The main results are as follows:1.Rice straw returning affected soil physicochemical characteristics significantly.Soil bulk density in rice straw returning treatments was lower than that without straw returning treatment.The soil bulk density under shallow rotary tillage with straw treatment was the lowest among these treatments at three-leaf stage,and it reached the minimum level in the straw deep bury treatment both at both jointing and booting stages.Bulk density of total straw returning treatments was lower than those of half amount straw returning treatments.The absolute moisture of ploughing soil was enhanced after rice straw returning.The value reached the maximum level in straw mulching mode,and that in total returning mode was higher than that in a half returning mode.Soil moisture of topsoil was decreased with wheat growth process.Different straw returning modes had different effects on the temperature of ploughing soil at different depths.When the atmospheric temperature was high,straw mulching mitigated the soil temperature fluctuation and had a significant warming effect when the atmosphere temperature was below zero degree.The temperature of 5-10 cm depth soil was more affected in different straw retuning modes,but the tempereture of 15-25 cm depth soil was less affected.2.Soil organic matter content in the 0-20cm surface soil at maturity was higher than that of the fertility of background soil,which was increased by 5.79 g/kg as compared with no straw returning.The highest content of soil organic matter was determined for the soils in the treatments of deep burial of whole amount straw returning,followed by whole amount straw mulching and no straw returning.Soil organic matter content in the 20-40 cm layer was significantly lower than that in the 0-20 cm layer,and the differences among these treatments were insignificant.Soil urease activity was increased in the 0-20 cm layer under rice straw returning treatment.It was higher in whole amount straw returning treatment than that in half amount straw returning,and reached the maximum level in the straw mulching treatment.Straw returning treatment had higher catalase activity than no straw returning treatment.Soil urease and catalase activity in the 20-40 cm layer were significantly lower than that in the 0-20 cm layer The alkali-hydrolyzable nirtogen content from four-leaf stage to booting stage followed a descedant order of no straw returning,deep burial straw retunring,straw mulching,and shallow tillage straw returning at half amount returning level,and in the order of straw mulching,deep bury returning,and shallow tillage returning at total amount straw returning level.After anthesis,the alkali-hydrolyzable nirtogen content changed and followed the order of straw mulching,deep burial returning,shallow tillage returning,all under the total straw returning to field condition.The nitrogen aplication ratio of 5:1:2:2 was more conducive to degrade straw than 7:1:2:0 aplication due to higher activitives of urease and catalase.3.The quality of soil tillage and preparation before sowing and emergence rate were significantly reduced.The growth rate and quality of wheat seedlings were also reduced by straw returning.The emergence rate was higher in the half amount returning treatments than that in the whole amount straw returning treatments.Shallow rotary tillage with whole amount straw returning had the lowest emegence rate,which was 10%lower as compared with that in no straw returning treatment.The highest emergence rate was in the treatment of half amount straw mulching,which was 3.4%higher than that in no straw returning treatment.Deep burial returning treatment had the least effect on emergence rate.Wheat seedlings grew best under half amount straw mulching treatment from three to five leaf stage.The grwoth of wheat seedlings was influenced to the greatest extent by the total amount straw mulching.In the present study,strong seedlings were sucessfully developed when the sowing depth was 3 cm and plump seeds with high 1000-grain-weight were used,and the negative effects of rice straw returning on seedling quality were mitigated.4.Rice straw returning affected the accumulation of nitrogen in wheat plants.In the present study,the accumulation of nitrogen and dry matter in straw returning treatments were less than those in no returning treatments before over-wintering,and the accumulation of nitrogen and dry matter in half amount returning treatments were higher than those in whole amount returning treatments.There was less accumulation at the nitrogen application ratio of 5:1:2:2 before jointing stage,and the nitrogen application ratio of 5:1:2:2 was more beneficial for dry matter and nitrogen accumulation than the nitrogen application ratio of 7:1:2:0 after anthesis.Its contribution rate of nitrogen accumulation after anthesis significantly increased.The SPAD readings of top-three leaves reduced slowly,the net photosynthetic rate of flag leaf was higher in straw returning treatment.and the treatment of half amount of straw returning had the highest SPAD reading.The SPAD readings after anthesis at the nitrogen application ratio of 5:1:2:2 treatment reduced more slowly than that at nitrogen application ratio of 7:1:2:0,At the same time,there was a higher net photosynthetic rate of flag leaf at the nitrogen application ratio of 5:1:2:2 treatment,which showed that increasing fertilizer at booting stage was beneficial to extend photosynthesis duration under straw returning treatment.5.The amount of rice straw returning and straw returning mode affected wheat grain yield of the subsequent cropping season significantly.In the present study,compared with the grain yield of no straw returning treatment,the grain yield was reduced in the treatments of shallow rotary tillage with whole amount of straw returning,convering of whole amount of straw returning and deep burial of whole amount of straw returning,but was increased in the treatment of half amount of straw mulching at 4500 kg/hm2.In the treatments with the same returning way,the yield was higher when the returning rate was 4500 kg/hm2 as compared with 9000kg/hm2.All treatments with nitrogen application ratio of 5:1:2:2 produced more grain than those with the nitrogen application ratio of 7:1:2:0,and the highest grain yield was achieved when the sowing depth was 3 cm.Straw returning mainly affected the formation of the number of spike and the grain number per spike.Beside,shallow rotary tillage reduced 1000-grain-weight,resulting in the decrease in grain yield.6.In the present study,the grain yield of Yangfumai 4 higher than 8000 kg/hm2 was obstained when the straw returning rate was 4500 kg/hm2 using straw mulching mode,the sowing depth was 3 cm,the planting density was 180×104/hm2,the application amount of nitrogen was 270 kg/hm2,the nitrogen application ratio of basic fertilizer and the fertilizer applied at tillering,jointing and booting development was maintained at both 5:1:2:2 and 7:1:2:0,and the applied rates of P2O5 and K2O were 150 kg/hm2 respectively. |
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