| Green manure,as a clean source of organic fertilizer,plays an important role in improving fertility and replacing chemical fertilizers,and is one of the important features of modern agriculture.With the rapid development of China's fruit industry,it provides a huge development space for the orchard green manure cultivation.The current research on green manure in orchards mainly focuses on the impact of green manure planting on soil and fruit trees,but on the suitable green manure varieties in different regions,the growth and development of different green manure varieties and the law of nutrient accumulation,nutrient release characteristics and influencing factors after returning to the field Lack of systematic research.To this end,this article firstly retrieved the 3431 data variables containing 17 kinds of common green manure in China by searching the green manure output and nutrient content of China How Net database and related books,and integratedly analyzed the output and nitrogen,phosphorus and potassium of common green manure in different regions of China The characteristics of nutrient content evaluated the potential of planting green manure to replace chemical nitrogen fertilizer in different regions.On this basis,based on citrus orchards,the growth and development and nutrient accumulation rules of different green manure varieties in southwest citrus orchards were studied through field trials;and soil moisture content,soil fertility,and different seeding were discussed through field trials or pot experiment The effects of the period and no-tillage on the growth of green manure;further,through field experiments and indoor cultivation experiments,the decomposition characteristics and nutrient release rules of green manure under different utilization patterns were studied.The aim is to screen out green manure varieties suitable for planting in citrus orchards,and to provide a basis for high-yield and efficient planting and utilization of manure in citrus orchards.The main findings are as follows:(1)The characteristics of yield and nutrient content of common green manure in different regions of China and the evaluation of alternative nitrogen fertilizer potential show that::The results showed that the average yield of fresh green manure in China was 38 t/hm2(moisture content was 81% on average),and associated with a wide range(0.7~187 t/hm2).The average yields of ryegrass,erect milkvetch,stylosanthes,and red clover were higher than 43 t·hm-2,and significantly higher than other green manure species.The average nitrogen concentration of 17 kinds of common green manures was 28 g/kg(On the hay).The nitrogen concentration of common vetch,vetch,alfalfa,burclover,and white clover were all above 30 g/kg,which was significantly higher than other green manure types.The average phosphorus concentration of different common green manures was 7.0 g/kg,and vetch and orychophragmus violaceus harbored greater phosphorus concentration above 8.0 g/kg than other green manures.The average potassium concentration of different common green manure was 25 g/kg,and the orychophragmus violaceus and milk vetch was highest with more than 32 g/kg potassium concentration.There were significant differences in the accumulation of nitrogen,phosphorus and potassium in different common green manures,among which the accumulation of nutrients was the highest in erect milkvetch,ryegrass,red clover,alfalfa,and stylosanthes,with 250 kg N hm2,50 kg P2O5 hm2 and 191.7 kg K2 O hm2,respectively.According to the nitrogen fixation potential assessment of the yield,nitrogen fixation amount and planting area of major leguminous green manure in different regions,the current planting area of green manure in China is about 4.49 million hm2,equivalent to the production of 400 ~ 810 thousand tons of nitrogen fertilizer.If we estimate the potential area of green fertilizer in China at 46 million hm2,which is equivalent to the production of 4.0 ~ 8.28 million tons of nitrogen fertilizer,leguminous green fertilizer has a high potential of fertilizer replacement.In the promotion and application of green manure,green manure varieties should be selected according to local adaptability of green manure and the characteristics of its yield and nutrient content.(2)Studies on the growth and development of green manure and accumulation of nutrients in citrus orchards have shown that: hairy vetch,smooth vetch,commom vetch,grass vetch,milk vetch,white clover,red clover,annual ryegrass,and orychophragmus violaceus grow between rows of young citrus orchards is good,and the aboveground yield gradually increases with the growth period.The highest yield of winter green manure(28.6-83.6 t/hm2)appears between the 160 th and 220 th days after sowing,which is the spring blooming period or prosperous periode.Among them,smooth vetch,hairy vetch,commom vetch,grass vetch,and annual ryegrass grow rapidly at the seedling stage,and the maximum yield of fresh grass above ground is above 55 t/hm2.After returning to the field,it can provide a lot of nutrients for citrus trees,and it is a high-quality and high-yield green manure variety suitable for citrus orchards.However,ryegrass is an upright plant,and its plant height is greater than 90 cm at 160 d,which is not suitable for planting in young citrus orchards.(3)Soil moisture significantly affects the germination and growth of green manure.The soil water content is between 75% and 100% of the maximum field water holding capacity.The germination rate of green manure seeds is the highest on the time.The difference between the two is not significant.The legume green manure and gramineous ryegrass increased the aboveground biomass with the increase of soil water content.When the soil water content reached the maximum field water holding capacity,the yield was the highest;when the water content was too low,the oxidase(POD,CAT,SOD)activity was high,Inhibit the growth of green manure.The cruciferous green manure grows best when the field water holding capacity is 75.0%.At this time,the activity of oxidase and the content of MDA are basically at the lowest state.Therefore,maintaining high soil moisture during sowing is a necessary condition to ensure the rapid germination of green manure seeds,early growth of green manure,and mulching of pressed grass.(4)Studies on the effect of soil fertility on the growth of green manure in citrus orchards show that: soil fertility significantly affects the yield of green manure above ground.High-fertility soils have significantly higher biomass and nutrient uptake than low-fertility soils.The soil showed lower production performance,and the highest yield was between 0.46 and 13.3 t/hm2 hairy vetch,smooth vetch,and commom vetch have a wide range of adaptability,and grow well on different fertile soils.The yields of high-fertility and low-fertility soils are 55.3~75.3 t/hm2 and 28.0~37.6 t/hm2,which can be used as poor site conditions and low fertility promotion and application of varieties of orchard grass.(5)Studies on the effects of different sowing dates on the growth of green manure show that the sowing date mainly affects the yield of green manure and has a smaller effect on its nutrient content.The sowing date is from September 21 st to October 11 th.Proper early sowing can increase the yield of green manure.The yield and nutrient accumulation of fresh leaves of hairy vetch,smooth vetch,commom vetch are maximized.The accumulation of Nitrogen,phosphorus,and potassium were 21.4~38.2 t/hm2,1507~2881 kg/hm2,91.9~205 kg/hm2,and 28.1~81.9 kg/hm2.Hairy vetch and commom vetch still have high yields when they are sown around October 21 st.They are suitable green manure varieties for citrus orchards for late planting.(6)The research on the effect of no-tillage soil on the growth of green manure showed that soil no-tillage and tillage mainly affect the early growth of green manure,and the effect on the growth of green manure gradually decreases with the growth of time,and the difference is between 190 d and 220 d not significant,and there was no significant difference in nutrient content and nutrient accumulation during this period.The tested green fat hairy vetch,smooth vetch,commom vetch,grass vetch,milk vetch can be planted light and simplified way of no-tillage direct broadcast in citrus orchards.(7)Studies on the degradation characteristics and nutrient release of green manure show that the degradation characteristics and nutrient release of different treatments under field conditions are similar.Green manure decomposition is divided into three periods: fast decay period(0~30 d)-medium speed decay period(30~60 d)-slow decay period(60~120 d),and the nutrient release rate is expressed as Potassium> Nitrogen> Carbon> Phosphorus,the cover ratio of green manure is better for decomposition and nutrient release,and the appropriate temperature and moisture promote the amount of green manure decomposition and nutrient release.Winter green manure is rolled or covered in April.The rapid decomposition of green manure is exactly in line with the nutrient requirements of citrus spring,which can provide a large amount of effective nutrients for citrus.In summary,different green manures have different growth and development,nutrient accumulation,and same nutrient release laws.Leguminous green manure hairy vetch,smooth vetch,commom vetch,have strong adaptability,and can grow higher yields and nutrient accumulation in citrus orchards in the southwest,and can be used for large-scale promotion and application. |
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