| The alfalfa grasslands,more than 7 years old and nearly 170,000 hm2,have suffered from serious degradation.The productivity of grasslands are decreasing and the quality of grass is poor,decreased grassland productivity and poor forage quality in Southern mountainous area of Ningxia.For this purpose,the experiment with randomized block design.Analyse and compare the effects of agronomic practices on yield,forage quality,soil physical and chemical properties of degraded alfalfa grassland of A1B1(deep pine 30cm+shallow spin 5cm),A1B2(deep pine 30cm+shallow spin 10cm),A2B1(deep pine 40cm+shallow spin 5cm),A2B2(deep pine 40+shallow spin 10cm),A3B1(deep pine 50cm+shallow spin 5cm),A3B2(deep pine 50cm+shallow spin 10cm),And using the membership function and the grey correlation method to comprehensively evaluate the improvement effect.The research results are as follows:(1)Subsoiling and shallow plowing had significant effects on alfalfa plant height,branch number,leaf-stem ratio,fresh-to-dry ratio and yield(P<0.05).Alfalfa plant height,hay yield and leaf-stem ratio reached the highest in A3B2 treatment,which increased by 17.89cm,5043.77kg·hm-2 and 0.38,respectively,compared with the control group.A1B2 treated alfalfa had the maximum number of primary branches(25.87).In the 0?30 cm soil layer,the total root length and root surface area of the alfalfa decreased under the treatment of deep pine and shallow rotation.Based on the analysis of the membership function of agronomic traits,it is concluded that A3B2 has the best effect on alfalfa productivity improvement.(2)The content of crude protein(CP),ether extract(EE),neutral washing fiber(NDF),acid washing fiber(ADF)and relative feeding value(RFV)of alfalfa hay were significantly affected by the treatment of subsoiling and shallow plowing(P<0.05),and the content of A3B2 was significantly increased by 4.6%compared with the control group.A1B2 compared with the control group,relative feeding value(RFV)and ether extract content of alfalfa increased by 27.15%and 0.6%respectively,and neutral(NDF)and acid detergent fiber(ADF)decreased by 4.11%and 3.05%respectively under this treatment.Based on the comprehensive evaluation of alfalfa hay quality by membership function,it is concluded that A1B2 treatment has the most significant effect on alfalfa quality improvement.(3)The treatment of subsoiling and shallow plowing had significant effects on soil bulk density,porosity and compactness(P<0.05),which could increase soil porosity of 0?60 cm,and also reduce soil bulk density of 0?20 cm and 40?60 cm and 0?40 cm.Each treatment improved soil moisture content and 6 soil fertility in 0?60cm soil layer to different extents.A3B1 is the best tillage mode for improving soil fertility by comprehensively evaluating the grey correlation degree of total nitrogen,total phosphorus,organic matter,available phosphorus,available potassium and alkali nitrogen.The comprehensive analysis shows that in the southern mountainous area of Ningxia,50cm subsoiling and 10cm shallow plowing can effectively improve the productivity of degraded alfalfa grassland.The quality of alfalfa was improved by 30cm subsoiling and 10cm shallow plowing.The 50cm shallow plowing 5cm subsoiling can effectively improve the soil fertility of degraded alfalfa grassland.In the production and application of degraded alfalfa grassland renewal and rejuvenation in the southern mountainous area,appropriate agronomic measures can be selected according to different needs. |
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