Effects of length and spatial distribution to the corn sowing quality in rapeseed straw returning

In order to reduce the adverse effects of rape straw return on corn sowing in the rape-corn rotation area in the middle and lower reaches of the Yangtze River. However, at present, indicators such as coverage rate (the proportion of straw covering the surface) and burial rate (the proportion of straw buried in the soil) are mainly used to evaluate the quality of straw returned to the field, which are not sufficient to fully express the spatial distribution characteristics of straw in the soil. Therefore, in this experiment, seeding characteristics such as corn germination rate and plant height were used as evaluation indexes. A 2-factor, 10-level one-way test was conducted to investigate the effects of rape straw length (6～150 mm) and the spatial distribution of straw in different depths of the soil (0～15 cm) on the evaluation indexes of corn emergence rate and plant height. The results showed that the emergence rate and plant height of maize decreased gradually and linearly with the increase of rape straw length, and for every 1 cm decrease in straw length, the emergence rate increased by 3.83%, and the plant height increased by 1.32 cm. This is because long straw will cause soil shelf, and the large void in the soil will lead to aeration and breathability, and it is difficult to achieve moisture conservation, which affects the seeding and seedling rooting, and results in the decline of emergence and survival rate. The shorter straw, the displacement of straw movement is greater, the more conducive to mixing with the soil, and short straw decomposition faster than long straw, the decomposition of nutrients can promote the development and growth of seedlings; when the length of the straw takes the minimum value of 6 mm, and the straw mass of the upper (≥0～5 cm), middle (≥5～10 cm) and bottom (≥10～15 cm) straw is the same (coefficient of variation of the straw mass is 0), the corn emergence rate reaches 100%, and the plant height grew up to 55.84 cm. When the length of rapeseed straw was the same and the mulching was uneven, the corn emergence rate and plant height were determined by the proportion of straw mass in the upper soil layer, the greater corn emergence rate and plant height for lower upper soil straw mass fractions; when the proportion of straw mulching mass in the upper soil layer was the same, the corn emergence rate and plant height were determined by the proportion of straw mass in the middle soil layer, and smaller middle soil stover mass share, then the corn seedling emergence rate and plant height is greater. The reason is that after returning the straw to the field and burying it in the shallow layer of soil, it will lead to the phenomenon that the straw and soil can not be mixed sufficiently, and there will occur the phenomenon of straw stacking and clumping, from the experimental results, the uniformity of spatial distribution of straw mass has a significant effect on seeding performance, but it is not the case that the more uniform the mulch is, the better the seeding performance is, so appropriately increasing the depth of straw burying can effectively improve the soil's ability of water retention, fertilizer retention and supply of fertilizer, at the same time, it can promote the distribution of roots, and continuous growth of root can promote the water and nutrients, which is conducive to the growth of crops; improve the degree of straw crushing, reduce the straw mass in the middle and upper layers, increase the proportion of straw mass in the bottom layer of the soil, and realize the deep burying of straw, which can help to improve the seedling emergence rate and the height of the plant. The results of this study provide theoretical support for the construction and quality improvement of high quality seed beds for straw return.