Effects Of Fertilization And Reseeding On The Productivity,forage Quality And Soil Properties Of Degraded Alfalfa Grassland

In order to solve the problems of low forage yield,poor quality,and soil nutrient loss caused by the degradation of alfalfa(Medicago sativa)grasslands over 7 years old in the semi-arid area of Ningxia,a two-factor randomized block design was adopted to study the effects of different P-K fertilizer application rates(A0(0-0 kg/hm2),A1(75-60 kg/hm2),A2(150-120 kg/hm2),A3(225-180 kg/hm2))and different supplementary sowing rates of grasses(Bromus inermis Leyss.,Elymus dahuricus Turcz.,and Festuca arundinacea Schreb.are mixed in a ratio of 1:1:1,and the reseeding rates are:B0(0g/m2),B1(3.14g/m2),B2(6.28g/m2),B3(9.42g/m2))on the performance of degraded alfalfa grassland,forage quality and soil physical and chemical properties.Then the grey correlation degree method and principal component analysis were used to comprehensively evaluate the improvement effect.The results show that:(1)Fertilization and supplementary sowing had significant effects on plant height,stem diameter,fresh-dry ratio,stem-leaf ratio and hay yield of alfalfa(P<0.05).The plant height and stem diameter increased first and then decreased with the increase of fertilization or reseeding,and plant height,stem diameter and hay yield reached the maximum under the A2B2 treatment.Under the same fertilizer application rate and supplementary sowing rate,the hay production of alfalfa in 2019 was higher than that in 2018 and 2020.(2)The content of crude protein and crude fat of forage increased gradually with the increase of fertilizer application(or supplementary sowing),and the content of crude ash,neutral detergent fiber and acid detergent fiber decreased gradually,and the relative feeding value increased.Under the same fertilization rate and supplementary sowing rate,the average relative forage value of the three-year forage reached the maximum under the A2B2 treatment,and increased first and then decreased with the extension of years.(3)Fertilization and supplemental sowing have significant effects on soil bulk density,porosity,water content and organic matter content(P<0.05),and had little effect on soil pH,which ranging from 7.7 to 8.3.Principal component analysis of various indicators of 0-20 cm surface soil showed that A2B2 treatment had a better improvement effect on the soil,followed by A3B2 and A2B1.(4)The grey correlation method and principal component analysis showed that A2B2 treatment ranked first,followed by A3B2 treatment and A2B1 treatment.It indicated that when the application rate of P-K fertilizer was 225-180 kg/hm2 and the supplementary sowing rate of grass was 6.28g/m2,the degraded alfalfa grassland had good improvement effect,which could improve the production performance of degraded alfalfa grassland,improve the quality of forage,and improve the physical and chemical properties of soil.