Effects Of Fertilization On Production Performance And Quality Of Alfalfa In Yinbei Saline-alkali Land

Alfalfa(Medicago sativa L.),known as the ’king of forage’,is a worldwide forage.Its efficient and high-quality production is particularly critical to the safety of feed grains.Making full use of the reserve cultivated land resources of saline-alkali land to produce high-quality forage such as alfalfa is particularly important for the sustainable,stable and healthy development of animal husbandry.At present,there are problems of poor quality and low yield in alfalfa planting in Yinbei saline-alkali land.This study aims at the scientific problems of unclear soil limiting factors and fertilization regulation mechanism affecting the production performance and quality of alfalfa in saline-alkali land.Through fixed-point sampling and field experiments,the soil limiting factors for improving the production performance and quality of alfalfa in Yinbei saline-alkali land,the effects of nitrogen and phosphorus addition on the production performance and quality of alfalfa in saline-alkali land,and the effects of combined application of organic and inorganic fertilizers on the production performance and quality of alfalfa in saline-alkali land were studied.The aim is to provide scientific basis and practical guidance for improving the production performance and quality of alfalfa in Ningxia Yinbei saline-alkali land.The main results are as follows:1.Soil nitrogen,phosphorus,pH and total salt content are the main factors affecting the production performance and quality of alfalfa in saline-alkali land of Yinbei.In 2021,the hay yield and plant height of alfalfa decreased with the increase of soil salinity.The crude protein content and relative feeding value showed an upward trend.Soil nitrogen and phosphorus are the limiting factors affecting the production performance and quality of alfalfa in saline-alkali land of Yinbei.In 2022,the hay yield and plant height of alfalfa decreased with the increase of soil salinity.The crude protein content and relative feeding value showed an upward trend in the first half of the year and a downward trend in the second half of the year.Soil nitrogen,pH and total salt content are the limiting factors affecting the production performance and quality of alfalfa in saline-alkali land of Yinbei.2.The effects of nitrogen and phosphorus addition on photosynthetic characteristics and production performance of alfalfa in different degrees of saline-alkali land were different.Under the control treatment,with the increase of soil salinity,the hay yield,plant height and net photosynthetic rate of alfalfa decreased,and the intercellular CO2 concentration,stomatal conductance and transpiration rate of alfalfa leaves increased first and then decreased.After applying nitrogen and phosphorus,the photosynthetic characteristics and production performance of alfalfa in different degrees of saline-alkali land were consistent with the control.Compared with the control,the net photosynthetic rate and stomatal conductance of alfalfa leaves were significantly increased by 10.56%and 32.81%,respectively.The net photosynthetic rate of alfalfa leaves decreased significantly by 14.54%after nitrogen application under low salinity.The hay yield of alfalfa was significantly decreased by 8.99%(P<0.05)after nitrogen application under high salinity.3.The effects of nitrogen and phosphorus addition on the quality of alfalfa in different degrees of saline-alkali land were different.Under the control treatment,the crude protein content and relative feeding value of alfalfa increased with the increase of soil salinity.In addition to the crude protein content under nitrogen treatment,after the application of nitrogen and phosphorus,the variation of alfalfa quality with the degree of salinity in different degrees of saline-alkali land was consistent with the control.Compared with the control,the crude protein content of alfalfa increased significantly by 7.27%after phosphorus application.The relative feeding value of alfalfa was significantly increased by 11.48%after phosphorus application under high salinity.The crude protein content and relative feeding value of alfalfa were significantly decreased by 4.96%and 9.23%(P<0.05)after nitrogen application under high salinity and alkalinity.4.The combined application of organic and inorganic fertilizers can significantly increase grassland productivity and improve forage nutritional quality.With the increase of organic fertilizer application,the hay yield and crude protein content of alfalfa increased first and then decreased.The hay yield was the highest under F2S treatment,reaching 3839.33 kg·hm-2.The crude protein content of F2S0 treatment was the highest(23.86%),and the relative feeding value was higher(161.81).5.The optimum fertilization mode and fertilization amount suitable for improving the production performance and quality of alfalfa in Yinbei saline-alkali land were proposed.The principal component analysis showed that under F2S0 treatment,organic fertilizer instead of 15%chemical fertilizer:organic fertilizer 675 kg·hm-2,N 76.5 kg·hm-2,P2O5 76.5 kg·hm-2,K2O38.25 kg·hm-2 was beneficial to improve the production performance of alfalfa,improve the quality of forage grass and increase soil nutrients.