| The main constraints to the sustainable development of agriculture in the Yellow River Delta are the lack of freshwater resources,soil salinization and low soil fertility.Traditional winter wheat cultivation is generally associated with low yield and instability,resulting in poor production benefits.Winter green fertilizer has unique advantages in soil structure improvement and soil power enhancement in saline sodic areas,but there is a relative lack of related studies in the Yellow River Delta region.In this study,four winter cropping patterns(winter fallow,winter wheat,Vicia villosa Roth and Orychophragmus vilogeniusus L.)were set at the Yellow River Delta Saline-alkali Agro-ecosystem Observation and Research Station,using maize as the succession crop,and three composite fertilizer application levels were set up: full fertilization(F100),15% fertilizer application(F85)and 30% fertilizer application(F70),to explore the effects of different planting patterns and green fertilizer applications on soil traits and maize growth.Meanwhile,decay tests were simulated by nylon mesh bags under two returned fields without and with pressure change,to provide a reference for the rational use of green manure crops in saline areas of the Yellow River Delta,and to provide some theoretical support and data basis for ecological protection and high quality development in the region.The main findings are as follows:(1)Planting winter and green manure is beneficial to some extent for soil quality improvement in the Yellow River Delta region.Compared with the fallow and winter wheat treatments,total nitrogen(TN)and total phosphorus(TP)were significantly increased under the 2 green manure treatments,but there were no significant differences among the green manure treatments,and no significant effects were found on EC,organic matter content and total potassium(TK).During planting,the two green manure treatments did not significantly affect soil p H.After turning the green manure,the p H significantly decreased under the two green manure treatments,with the greatest decrease occurring in the Vicia villosa Roth treatment.Compared with the other treatments,fallow treatment increased soil water stable large aggregate content above0.25 mm(increased by 5.22%～19.61%).Considering the effect on soil physicochemical properties,Vicia villosa Roth performed better as a winter cover crop on the Yellow River Delta,with the Orychophragmus vilogeniusus L.(2)In the present experiment conditions,Vicia villosa Roth provided more nitrogen,phosphorus and potassium nutrients compared with Orychophragmus vilogeniusus L.The release process of dry matter and nutrient cumulative decomposition process of the two green manures were fast at the early stage,slow at the later stage,and finally gradually leveled off.Under the two kinds of returning methods,the nutrient release rate of Vicia villosa Roth was expressed as potassium >phosphorus > carbon ≈ nitrogen,and the Orychophragmus vilogeniusus L.showed as potassium > phosphorus > carbon > nitrogen.By the maize maturation stage,the cumulative decay rate of dry matter and the cumulative releases of carbon,nitrogen,phosphorus,and potassium from the Vicia villosa Roth were 76.14%,84.41%,83.58%,90.96%,91.25%,respectively,in no-tillage mulch returning fields;The corresponding indicators were 58.76%,79.10%,59.23%,80.11%,78.81% for Orychophragmus vilogeniusus L.The cumulative decay rate of dry matter and the cumulative releases of carbon,nitrogen,phosphorus,and potassium from the Vicia villosa Roth were 81.38%,85.52%,85.16%,90.48%,95.13%,respectively,in the eversion return field;The corresponding indicators were 78.90%,82.08%,77.82%,89.94%,96.58% in Orychophragmus vilogeniusus L.Overall,the rates of dry matter decay and nutrient release for the two green fertilizers were higher in the returned than cover.The dry matter decomposition rate and nutrient release rate of Vicia villosa Roth were higher than those of Orychophragmus vilogeniusus L.,but the overall release rate of them was slower,extended the supplying time,and the sustained supply capacity of each nutrient under the cover field was better.(3)Green fertilizer application was beneficial to a certain extent for improving soil quality during the maize growth period.There were no significant differences in p H,EC,and TP among the treatments,with the lowest values at harvest stage in the Maize Treated with Vicia villosa Roth.Under the same fertilizer application,compared with the fallow treatment,the treatments with the two green fertilizers significantly increased the TN and TK contents,but the organic matter contents decreased by 0.53% ～10.44%compared with the winter wheat treatment.The nutrient content still maintained or increased after the reduced fertilization treatment under the same planting mode.Compared with the other treatments,the application of reduced fertilizer with Orychophragmus vilogeniusus L.increased the amount of soil water stable large aggregates above 0.25 mm(1.16%～27.53%),and reduced 30% fertilizer increased more of nutrient content.(4)Fertilizers applied with green manure significantly increased the maize plant height,stem thickness,aboveground biomass and grain yield.Under the same fertilizer application,compared with the fallow,winter wheat treatments,all growth indicators were improved in the two green manure treatments,with the greatest increase in plant height,stem thickness and in the Vicia villosa Roth treatment,while the shoot biomass and grain yield in the above ground were highest in the Orychophragmus vilogeniusus L.treatment.The levels of each indicator were maintained or increased after the two reduced fertilization treatments compared with F100 under the same planting mode.Reduction of 30% treatment by planting Orychophragmus vilogeniusus L.combined with fertilizer resulted in 22.28% higher yield while effectively reducing fertilizer application compared with planting winter wheat under equivalent fertilization conditions,and considering the environmental and economic benefits comprehensively,it was the reference planting mode available in this area.However,the present study is a short-term trial outcome that remains to be validated in practices with long-time scales.In summary,the rotation of two green manures,Vicia villosa Roth and Orychophragmus vilogeniusus L.,in saline areas of the Yellow River Delta can enhance the nutrient content of the soil as well as the content of soil macromolecules and soil stability,thus improving the yield of the next crop of maize.The nutrient content of green manure can be maintained with reduced fertilizer application.The treatment of Orychophragmus vilogeniusus L.with 30% reduced fertilizer improved soil properties and maize yield better during this experiment,which can be used as a reference planting pattern in the experimental area.However,the field experiment is susceptible to the influence of external environment and should be continuously verified on a long-time scale in the future to provide a reliable basis for ecological protection and high quality development of saline lands in the Yellow River Delta. |
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