No abstract

Drip irrigation under mulch is a widely used technique in the arid region of northwest China. The partially mulched soil and the bare strips between mulched areas may complicate the migration of water, salt, and heat in soils, and cause lateral salt accumulation on bare soil surfaces. For investigating hydrothermal dynamics and salt distribution patterns under such circumstances, tank experiments with drip irrigation under plastic film on partially mulched soil were conducted under two intensities of drip irrigation (i.e., low (W1) and high (W2)) with the same total irrigation amount. The spatial distributions of soil water, temperature, and electrical conductivity were monitored accordingly. The two-dimensional (2D) model of soil water, salt, and heat transport under drip irrigation and partially mulched soil conditions was established using HYDRUS-2D, and kinetic adsorption during salt migration was considered. The results of the experiments showed that the uneven distribution of the hydrothermal state led to the accumulation of salt on the un-mulched soil surface. Water migrated from where the dripper was located, and heat accumulated mainly in the mulched soil. HYDRUS-2D matched reasonably well with the observed data, with an R2 higher than 0.54. Under the partially mulched conditions, lower intensity of drip irrigation (W1) show higher desalination efficiency in root zones, with less even lateral salt distribution. Scenario simulations further demonstrated that a larger total irrigation amount would result in a larger desalination zone, and drip irrigations with appropriate incremental intensity could improve salt leaching in the root zone with increased lateral migration of water.

Biodegradable film is a promising alternative to polyethylene film in arid regions, but its use is usually inhibited by its high cost and elusive effects on soil and crop yield. A two-year field experiment was carried out to explore the impact of biodegradable film on soil hydrothermal dynamics, yield, water productivity and economic benefits under three irrigation strategies (full, medium and low irrigation amount) compared with non-mulching and polyethylene film. The comprehensive benefits (economic, technical and ecological) of different film mulching patterns were evaluated using analytic hierarchy process and gray relational analysis methods. The results indicated that increasing irrigation amount could accelerate the degradation of the biodegradable film, with the highest film weight loss rate of 38.8% obtained under full irrigation. Film mulching could mitigate the negative impact of water deficit on crop yield, with the yield of biodegradable film and polyethylene film enhanced by 11.6% and 18.6% compared with non-mulching under low irrigation. Although polyethylene film showed the highest economic benefits, non-mulching showed the highest comprehensive benefits. Only when the price of biodegradable film material dropped to less than 1.37 times that of polyethylene film did the economic benefit of biodegradable film outcompete non-mulching and become a more acceptable and promising farming solution to boosting environmental sustainability.