Productivity and soil response to plastic film mulching durations for spring wheat on entisols in the semiarid Loess Plateau of China

Plastic film mulching is an important agricultural practice in semiarid areas of the Loess Plateau in northwest China to improve crop productivity by changing soil properties. We conducted field experiments using spring wheat (Triticum aestivum L. cv Lonochun 8139-2) to examine the effect of film-mulching with varying durations on crop yield and soil properties in 1999 and 2000 on Loess Orthic Entisols in the semiarid Loess Plateau of China. The three mulching treatments with varying durations were applied: (1) M30: mulching for 30 days after sowing (DAS); (2) M60: mulching for 60 DAS; (3) Mw: mulching for the whole growth period, as well as the control; MO: without mulching. In 1999, seedlings from the three mulching treatments emerged 8 days earlier than those from unmulchingly treated. In 2000, a very dry year, emergence of seedlings in the mulching treatments occurred only 1-2 days earlier compared to control. Moreover, mulching treatments also significantly increased the total root biomass before 90 DAS in 1999 and before 30 DAS in 2000. There was a sharp increase in soil respiration in the mulching treatments. Soil microbial biomass nitrogen content in the Mw treatment was significantly lower at 43 DAS than that in control. Accumulation of total mineral nitrogen in the soil at harvest was clearly higher in Mw than in the other treatments and the control. Highest yields were recorded from wheat treated with M60 (3305 and 1203 kg ha(-1) in 1999 and 2000, respectively). By contrast, no significant difference in yield was found among the three-mulched treatments in 1999. In 1999 the water use efficiency in all mulching treatments was significantly higher than in control, while in 2000 it was significantly higher in M60 and Mw than in M30 and control. These findings therefore suggest that mulching for 60 DAS increased grain yield by increasing the mineral nitrogen, soil water and the efficiency of water use and avoiding the over-decomposition of organic matter and over-mineralization of organic nitrogen. (C) 2004 Elsevier B.V. All rights reserved.