Effects of Straw Returning and Irrigation Methods on Seedling Emergence and Growth in Soybean and Maize Strip Intercropping

Soybean and maize strip intercropping is an important cultivation pattern for soybean productivity improvement project in China. In this experiment, the effects of straw returning and irrigation methods on the emergence and seedling growth quality in soybean and maize strip intercropping were investigated, in order to provide the theoretical support for the strip intercropping to solve the problem of seedling emergence.

The experiment was carried out in Yucheng City, Dezhou City, Shandong Province and Anju District, Suining City, Sichuan Province in 2022 and 2023, respectively. Two-factor split plot zone design was adopted, three straw returning methods (non-returning straw (S1), returning straw with no stubble (S2), and returning straw with stubble (S3)) and three irrigation methods (non-irrigation (W1), check irrigation before sowing (W2), and spray irrigation after sowing (W3)) were set up, and their effects on seedling emergence and growth of strip intercropping crops were researched.

Irrigation could significantly increase soil water content and alleviate soil compactness, thus effectively improving the emergence rate of soybean and maize, and shortening the emergence time. The seedling emergence rates under W3, W2 and W1 with S2 were 71.00%, 45.70% and 38.50% in Yucheng, respectively. The seedling emergence rates under W3, W2 and W1 with S2 were 90.17%, 88.50% and 61.67% in Anju, respectively. The emergence time under W2 and W3 was 3.29 d and 2.92 d shorter than that under W1, respectively. Under different irrigation methods, there was no significant difference in the seedling emergence rate of maize, which could reach more than 90%, but the seedling emergence time was significantly different. The emergence time of maize under W2 and W3 was 1.9 d and 3.1 d shorter than that under W1 in Yucheng, respectively. The emergence time of maize under W2 and W3 was 0.96 d and 0.6 d shorter than that under W1 in Anju, respectively. Straw returning significantly increased soil water content and decreased soil compactness, and the effects in both places were S2>S3>S1. Straw returning to the field under W1 could significantly improve the soybean seedling emergence rate in Yucheng, in which S2 was 45.08% higher than S1. Straw returning had no significant effect on the emergence rate of maize in the two places. Straw returning and irrigation significantly increased the activity of soybean lipase (LPS) and maize α-amylase (α-AL). The LPS of W2 and W3 were 26.86% and 37.77% higher than that of W1, respectively. The LPS under S2 was 14.14% and 18.05% higher than that under S3 and S1, respectively. The α-AL under W2 was 189.47% higher than that under W1, and the α-AL under S2 was 61.52% and 127.33% higher than that under S3 and S1, respectively. The two irrigation treatments could promote the growth and development of soybean and maize, and improve the seedling growth rate and uniformity. The soybean plant height under W3 and W2 was 21.74% and 15.70% higher than that under W1, respectively, wihle the stem diameter was 12.52% and 28.15% higher, respectively, and the leaf area was 11.84% and 38.78% higher, respectively. The maize plant height under W3 and W2 was 21.80% and 20.62% higher than that under W1, respectively, while the stem diameter was 37.69% and 26.39% higher than that under W1, respectively, and the leaf area under W3 was 36.56% and 73.33% higher than that under W2 and W1, respectively. Straw returning significantly affected the growth of maize seedlings in Yucheng, showing S3>S1>S2. The plant height under S3 was 19.92% and 27.31% higher than that under S1 and S2, respectively, while the stem diameter was 27.59% and 59.80% higher, respectively, and the leaf area was 42.76% and 68.54% higher, respectively.

Successful emergence and construction of a good seedling population were the basis for achieving high yield. Spray irrigation after sowing improved the physical structure of the plough layer, thus promoted the emergence of seedlings and shortened the emergence time in strip intercropping, and provided favorable conditions for subsequent crop growth. Returning straw with stubble could improve the growth quality of strip intercropping seedlings in Yucheng. Returning straw with no stubble had the characteristics of water storage and alleviating soil compaction, it is beneficial to soybean emergence without irrigation, and has a promoting effect on the formation of strong seedlings of strip intercropping crops in Anju.