| Plastic film mulched furrow-ridge cropping is a recent modification of maize cropping pattern. By excluding evaporation, redistributing precipitation from ridges to furrows and increasing soil temperature, plastic film mulched furrow-ridge pattern can significantly enhance maize grain yields and thus it has been widely extended on semiarid Loess Plateau for maize production. However, the sustainability of soil fertility, and related soil managemental practices have been limitedly studied under continuous application of this cropping pattern. This research was therefore designed to investigate effects of plastic film mulched furrow-ridge maize cropping on soil quality and the possibility of introducing the soil incorporation of maize straws into this cropping pattern. The research site (35°54'N,104°05'E) was located at Xiaokangying, Yuzhong County of Gansu Province, with an altitude of 2013 m and annual precipitation of 388 mm. The experimental design included four treatments, namely, nil-straw incorporation plus nil-mulch (control), straw incorporation (S), film mulch (M), and straw incorporation plus film mulch (S+M), on a furrow-ridge micro-relief-prepared field. When seeding in 2009 and 2010, nitrogen and phosphorus were applied at 276 kg N/ha as urea (46% N) and at 39.3 kg P/ha as calcium superphosphate (5.2% P) in all treatments. The experiment started in March 2009 and ended in October 2010, being replicated for three times. The results are as follows:(1) Compared to control, M and S+M treatments improved maize grain yields by 89-105% and 93-136%, whereas S treatment did not affected maize grain yields. The total biomass was significantly increased by M or S+M, compared to control. Maize grain rainfall use efficiency and total biomass rainfall use efficiency were significantly increased by M or S+M, whereas S treatment had no difference with CK. When harvested, the concentration of nitrogen and phosphorus in different maize organs were not statistically affected by S, M or S+M, compared to control, but the recovery of nitrogen and phosphorus amount under M or S+M was significantly higher than that in CK. Our results showed that film mulch increased nutrient use efficiency significantly.(2) M treatment improved soil temperature for the top 20-cm layer through maize growth season each year, especially in the seeding stage. Over two years, M treatment improved soil temperature for the top 20-cm layer by 1.1-2.9℃, compared to control. Film-mulched furrow-ridge cropping increased soil water content for the top 15-cm layer through maize growth season each year, especially in the seeding stage, but it could make maize consume deep soil moisture.(3) Over two years, total soil organic carbon and total soil nitrogen concentrations were not changed by S, M or S+M, compared with control. However, M inclined towards decreasing but S or S+M treatment showed increasing particulate organic carbon and light organic carbon concentrations in soils. The increasing effect in particulate or light organic carbon pool with S+M treatment was more significant when compared to M than compared to control. Compared to control, M treatment decreased soil C/N, whereas S and S+M treatments did not affected Soil C/N. Soil NO3--N and total mineral nitrogen concentrations were significantly increased by M or S+M, compared to control, whereas S treatment had no difference with CK. Soil NH4+-N concentration was relatively stable and was less affected by farming methods. S+M treatment significantly decreased total mineral nitrogen concentration, when compared to M, so we concluded that introducing the soil incorporation of maize straws into film-mulched furrow-ridge cropping pattern could decrease the total mineral nitrogen concentration caused by film mulch to some extent. Soil available P was not statistically affected by film mulch (M) but it was significantly increased by S or S+M, compared to control.(4) Generally speaking, soil microbial biomass carbon and activities ofβ-glucosidase, alkaline phosphatase and urease were increased by S, M or S+M, compared to control. Over two years, microbial biomass carbon and activities of three enzymes under S+M treatment were higher than that in S and M. Further, soilβ-glucosidase, alkaline phosphatase and urease activities all positively correlated to soil microbial biomass carbon concentration over treatments and periodical measurements for two experiment years, respectively.Our preliminary results showed although plastic film mulched furrow-ridge cropping markedly increased maize grain yields, rainfall use efficiency and nutrient use efficiency but may have a potential to decrease soil organic carbon pool and cause soil total mineral nitrogen abundant accumulation; it was feasible to introduce maize straw into this cropping system for a favorable soil organic carbon balance, microbial activity and soil total mineral nitrogen.
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