Simulation and experiment of the hydrothermal coupling characteristics of seedbed under cotton ultra-wide film mulching conditions

Extra-wide film sowing can be expected to strengthen cotton seedlings during production. Among them, the handover row is reduced to increase the effective lighting surface. This study aims to clarify the hydrothermal coupling characteristics of the seed beds for the mechanized sowing with the extra-wide membranes. The seedbeds after mechanized sowing of cotton were taken as the research objects. A systematic investigation was then made on the influencing on the growth and development of cotton. Two treatments were carried out: 4.4-meter extra-wide film (T1) and 2.05-meter membrane (T2). The seed beds were hydrothermally simulated to monitor the cotton growth. The results showed that the HYDRUS model was performed better to simulate the hydrothermal properties of the seed bed after sowing. The simulated values were in the good agreement with the measured ones. The correlation coefficient R2 was above 0.97, and the mean absolute error (MAE) and root mean square error (RMSE) were close to 0, respectively. The moisture content and temperature of the T1 increased by 9.7% and 5.3%, respectively, compared with the T2. The deep moisture content and temperature increased by 2.8% and 3.6%, respectively, and the water storage and effective accumulated temperature of tillage layer increased by 9.3% and 18%, respectively. The emergence rates of the T1 and T2 were 91.7% and 89.8%, respectively. The better growth was observed in the T1. The plants height and stem diameter of the T1 increased by 6.7% and 11.5%, respectively, during the whole growth period, compared with the T2. The number of the cotton bolls and the weight of a single boll in the T1 were 6.16 and 6.3 g, respectively. The cotton bolls were distributed in the middle and upper layers. While the number of cotton bolls and the weight of a single boll in the T2 were 6.03 and 5.9 g, respectively. The cotton bolls were distributed in the middle and lower layers. The yield of the seed cotton increased by 9.1%. Comprehensive analysis show that the mechanized sowing of the extra-wide film shared a better hydrothermal environment of the seed bed, due to the great variation in the structure of the seed bed. Much more nutrients were gained to rapidly, uniformly, evenly and strongly promote the emergence of the cotton seedlings. The better growth was achieved, according to the indicators of the cotton growth and development. The overall growth period increased by 3~5 days. The number of cotton bolls increased to optimize the distribution structure of the cotton bolls. The yield of seed cotton was also enhanced under the efficient mechanized planting.