| Green manure-corn-soybean rotation is one of the common cultivation models.There have been a lot of studies on the rotation system of green manure crops and other crops at home and abroad.In order to investigate the effect of the green manure-corn-soybean rotation system on crop yield and quality,the changes in soil physical and chemical properties under the rotation system,and the impact on soil carbon dioxide emissions,the impact of the rotation system on agricultural production in southern China was determined.The study used winter green manure crops（rye grass and white clover）as plant cover crops,compared with winter weed leisure as a control,combined with different farming methods（no-till,rotary tillage）,and obtained the following results through experiments and data analysis:（1）During the first harvest period of cover crops,the yield of no-tillage ryegrass reached44.67 t·hm-2,which was significantly higher than that of other treatments.At the same time,there was a very high amount of nitrogen,phosphorus,and potassium returned to the field,which was significantly higher than other treatments.In the second harvest period,the yield of cover crops harvested in the field includes the total yield of cover crops and weeds.The yield of cover crops in rotary tillage treatment is significantly higher than that in no-till treatment.However,the yield of mulch crops in the second harvest was lower than that in the first crop,of which the ryegrass yield decreased significantly,and the minimum yield of no-till ryegrass was only 4.89 t·hm-2,and indicated that ryegrass can inhibit the growth of weeds after spring harvesting.（2）The corn yield of ryegrass under no-tillage treatment was 6.79 t·hm-2 higher than that of rotary tillage ryegrass,and it was similar to the corn yield of white clover and bare land under rotary tillage treatment.Corn stalks treated with ryegrass had the highest amount of nitrogen,phosphorus and potassium returned to the field.Tillage methods have no significant effect on soybean yield and quality,but the yield of soybean under no-till ryegrass treatment is 3.19 t·hm-2,which is higher than 3.08 t·hm-2 of rotary tillage.（3）During the growth of green manure crops,the soil temperature of no-tillage ryegrass rose sharply,the peak value of soil water content was the highest,and the lowest valley value of the soil free bulk density was the lowest.The soil bulk density of no-till ryegrass was reduced by 0.02 g·cm-3 compared to before planting.It shows that no-tillage ryegrass has thermal insulation and water-retaining effect on the soil,at the same time it will reduce soil bulk density.（4）Rotary tillage ryegrass has the highest total nitrogen content in the soil,which may be due to the higher nitrogen return of ryegrass.No-tillage ryegrass treatment soil total phosphorus content did not change significantly,while the rotation of ryegrass rose the most.During the growth of cover crops,the total phosphorus content of the soil under no-tillage treatment is higher than that of rotary tillage treatment.It may be that the no-tillage cover crops can effectively reduce the amount of soil phosphorus leaching.（5）The annual total carbon dioxide emissions of the rotary tillage ryegrass are up to5638.35 g·m-2·y-1,while the total annual carbon dioxide emissions of the no-tillage ryegrass are 4978.09 g·m-2·y-1.It shows that no-tillage ryegrass can effectively control carbon dioxide emissions from soil.In summary,and through the comprehensive scoring method,it is concluded that no-till winter ryegrass is a suitable field planting model for the green manure-corn-soybean rotation system.It has advantages in the amount of green manure nutrient return,crop quality and yield,soil properties,and soil carbon dioxide emissions.This rotation system that uses plant cover crops is a new way to reduce the impact of fertilizer and herbicide inputs on field farmland while ensuring basic yield.. |
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