| In order to make rational use of the light and heat resources in arid and semiarid areas ofNorthwest China during summer fallow period, increase the productivity of land in LoessPlateau, determine the effects of green manure cropping on soil fertility and moisture andestablish and improve the cropping system with green manure multiple cropping, a fieldexperiment, with bare fallow and no-tillage as control (CK), was conducted to study theeffects of planting different green manures during summer fallow on the soil water content,soil nutrients and crop yield in a winter wheat field in Yangling of Shaanxi. Smooth Vetch(Vicia villosa Rothvar), Hairy Vetch (Vicia villosa Roth), Milk Vetch (Astragalus sinicus),Sweet Clover (Melilotus suaveolens Ledeb.) were chosen as the green manure treatments. Themain conclusions are as follows:1. The soil moisture content in0-200cm soil layer of green manure treatments werelower than the control in main growth periods of winter wheat in two years. The first year ofthe green manure treatments was significantly lower than of the summer fallow in eachgrowth stage of winter wheat. In the following year, the difference was reduced with thetreatments of green manure and the control.The most apparent effect on soil moisture in thedepth of0-60cm, followed by that of the deep soil (below120-140cm), and that of the60-140cm soil layer was the lowest.After green manure crops returned to field, the differenceof the soil moisture content in0-200cm soil layer between green manure treatments and thecontrol increase gradually with the development of winter wheat. The difference of it wasrelevant to the biomass of green manure. For two years, Milk vetch’s biomass is minimumand the treatment has the lest influence on soil moisture. There was not significant differenceon soil moisture of the treatments of Smooth Vetch, Hairy Vetch and Sweet Clover duringwinter wheat growth in these two years.2. The contents of the available and total nutrient were increased by planting greenmanures. The amount of the increase is mainly controlled by the nutrient content of greenmanure and its biomass. The increase of organic matter content comes mainly from the biomass of green manure. The shoot and the total biomass of Smooth Vetch the first year isthe largest, the organic matter content of the treatment was the highest as the winter wheatsowing and harvesting. From analysis of the effect different green manure on different soilnutrient contents in the depth of0-60cm during winter wheat growth, the soil availablenutrients, Total N and Total P of Smooth Vetch treatment are greatly improved; Hairy Vetchtreatment increased significantly the content of Available K and organic matter; Milk Vetchtreatment had a stronger effect to Available P and Hydro-N; Sweet Clover treatment couldobviously improve the content of Hydro-N. With the growth of winter wheat, the impact ofMilk Vetch on soil nutrient has gradually weaken in comparison with other green manuretreatments.3. Planting green manure crops consumed the content of NO3--N in the depth of0-60cm.The influence of it was not obvious on the content of NH4+-N. The content of NO3--N ofdifferent soil layers showed no trend of decreasing in the same period and the content ofNH4+-N was not significant difference. Planting green manure delayed the growing period ofwinter wheat. After winter wheat harvested, the content of NO3--N of green manuretreatments were lower than that of the control and the content of NH4+-N of Hairy Vetch,Milk Vetch and Sweet Clover treatments were lower than the control significantly in0-60cmsoil layer.4. Planting green manure crops during summer fallow period could improve the the plantheight, the flag leaf area and dry matter accumulation of winter wheat. From winter wheatjointing, heading, filling to maturing, the plant height of green manure treatments wereincreased followed8.54%～16.63%(P＜0.05),6.31%～11.36%(P＜0.05),6.67%～8.83%(P＜0.05) and5.60%～9.30%(P＜0.05) than CK. The flag leaf area of green manuretreatments was higher than CK and the treatments of Smooth Vetch, Hairy Vetch and SweetClover were significant differences. The dry matter accumulation’s difference between greenmanure treatments and the control increase gradually in the later growth period of winterwheat. Planting green manure crops could slightly increase the chlorophyll relative contentand delay leaf senescence.5. During summer fallow period planting green manure crops, the soil moisture of wheatfield was consumed, the soil water storage was reduced, but the water use efficiency wasraised. Compared with green manure treatments, the soil water storage of the controlincreased by2.1～5.0%(P＜0.05) and8.7～9.9%(P＜0.05)in winter wheat sowing andharvesting. On green manure growing period, the water consumption of green manuretreatments in0-200cm soil layer were2.5%～6.6%(P＜0.05) higher than CK. On winterwheat growing period, various treatments had no difference significantly. The water use efficiency (WUE) of green manure treatments (Smooth Vetch, Hairy Vetch, Milk Vetch andSweet Clover) were increased by15.7%(P＜0.05),20.2%(P＜0.05),3.3%and6.5%, ascompared to the control.6. The ear number per unit area, grains per ear and1000-grain weight of winter wheathas greatly improved by planting green manure and increased by30.5%～51.9%,27.6%～37.4%and3.79%～10.93%respectively. There was no significant difference between greenmanure treatments of the ear number per unit area and grains per ear. The1000-grain weightof Milk Vetch treatment was significantly lower than other green manure treatments. Theorder of winter wheat’s biomass and grain yield is B>A>D>C>CK. The biomass and grainyield of Smooth Vetch and Hairy Vetch were increased by23.9%,30.7%and21.1%,24.3%than the control. There was no significant difference between other green manure treatmentsand CK. Smooth Vetch and Hairy Vetch treatments winter wheat yield significantly in thisstudy selected as green manure crops. |
