| Weibei Dryland in South part of Loess Plateau is an important area for cereal production in Shaanxi Province. However, the great variation of the limited precipitation and the barren soil induce the low utilization of the precipitation and heat during traditional summer fallow period, result in unreliable income for local farmers. Discussion on the effects of leguminous green manure(LGM) based cropping system on soil fertility, crop yield, economic benefits is crucial to refine the cropping system, secure farmers’ income and eventually propel sustainable agriculture. This research based on a 4 years field experiment which applied summer fallow-winter wheat(SW) as a control, the ecological and economic benefits of LGM-winter wheat(LW) and LGM-spring maize-winter wheat(LMW) were studied(LW contained 3 treatments: green manure early mulch, early incorporation and late incorporation. LMW also consisted of 3 treatments: after the grain harvest of the legume, the residue was treated differently: straw mulch, straw incorporation and move-away). The primary results are listed below:Compared to SW, LW consumed extra soil water and this consumption increased with the decrement of summer fallow precipitation, worsen the drought, thus the wheat yield which relied mainly on natural precipitation fluctuated a lot. The nitrate stored in 0-200 cm soil after wheat harvest of LW was significantly higher than SW and LMW and might result in an increased risk of nitrate leaching. Soil organic carbon(SOC) content of green manure early mulch treatment under LW was 8.43 g·kg-1, significantly higher than that of SW(7.82 g·kg-1). The storage of soil organic carbon(SSOC) of this treatment in 0-20 cm was 20.75 Mg·hm-2, higher than the value when this experiment was started in 2009. The soil water before wheat seeding of LWM had no significant difference compared to SW, but was significantly higher than that of LW, therefore the wheat yield was more stable than LW. This rotation had less nitrate stored in 0-200 cm soil after wheat harvest when compared to LW. For LMW, the SOC of straw mulch treatment was 8.36 g·kg-1, the highest one of this rotation. It increased significantly compared to straw move-away treatment(7.78 g·kg-1) and SW. The SSOC in 0-20 cm soil was 20.58 Mg·hm-2, higher than the value when the experiment was conducted in 2009.The cost of LW was about 30 % higher than that of SW. In addition, the unstable and low wheat yield had led to the lowest economic performance and high coefficient of variation(C.V.) of net benefits(67.69 %). This suggested that LW had no advantage over SW, and it couldn’t replace the traditional SW. The difference of crop yield and total income among green manure treatments varied from year to year. LMW had the highest income and the lowest C.V.(15.42 %) of net benefits among the 3 rotation systems, implying that farmers could achieve a high and stable income by applying this rotation. Crops yield and economic benefits were higher under straw mulch and straw incorporation treatments than move-away treatment for LMW.LMW with straw mulch could increase soil water storage, improve soil fertility and also decrease residual nitrate stored in 0-200 cm soil. From the perspective of farmers’ income, the yield of this system is reliable and could achieve an output-input balance and sable income. Thus the comprehensive performance of LMW is the best and can be treated as a choice for sustainable agriculture. |
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