苜蓿生长年限对其产量及土壤性状的影响

Effect of alfalfa growth years on its yield and soil characteristics

采用田间测产的方法对3～26年不同生长年限苜蓿的产草量及采集0～20、20～40、40～60cm和80～100cm土层土样分析其含水量、容重、有机质含量变化，结果表明：随着生长年限的延长，苜蓿产量呈现先增加后降低的过程，6年生苜蓿干草产量达到最高，为9738kg／hm^2；在各个土层中，3～12年生苜蓿地土壤含水量变幅较大，变幅在7．90％～17．46％之间，主要发生在80～100cm土层，12年后土壤含水量变幅平稳，变幅在7．24％～12．66％之间；在各生长年限土壤容重大小依次为20～40cm〉40～60cm〉0～20cm，80～100cm土层土壤容重变化较平稳，生长年限越长土壤容重越小；3年生苜蓿地土壤有机质含量最低，各土层分别为1．59、1．82、2．42和2．08g／kg。4～18年生苜蓿地土壤各土层，随生长年限延长土壤有机质含量有所降低，各土层变化幅度分别在10．41～12．75、8．02～9．73、6．49～10．09、7．74～12．58g／kg之间，18年后有机质含量开始升高，各土层分别增加了2．69、1．39、1．37和0．97g／kg。研究证实了随着苜蓿生长年限的延长，苜蓿有退化趋势，土壤含水量、容重、有机质有下降的趋势。

By method of field investigation the yield of alfalfa with different growth ages from 3～26 years was determined and the soil samples from 0～20, 20～40, 40～60 cm and 80～100 cm layers were collected to analyze the variation of soil moisture, volumegric weight and organic matter. The results indicated that the yield of dried alfalfa increased and then declined with alfalfa growth ages increasing. The yield of 6 - year alfalfa was the highest, reaching 9 738 kg/hm^2. In each of layers, greater variation amplitude was in water content of soil with 3 to 12 - year alfalfa, ranging within 7.90 % ～ 17.46 %, and the variation mainly occurred at 80～ 100 cm soil layer. For soil with more than 12 - year alfalfa, the variation amplitude in water content, ranging 7.24 % ～ 12.66 %, was smooth. The layer of soil volumetric weight in decreasing order was 20～ 40 〉 40～ 60 〉 0～20 cm. The soil volumetric weight of 80～ 100 cm soil layer was smooth. The soil organic matter content with 3 - year alfalfa was the lowest of those years. The soil organic matter content of the order layer was 1.59, 1.82, 2.42 g/kg and 2.08 g/kg. The soil organic matter content of soil with alfalfa growth ages increasing from 4 years to 18 years at each of soil layers, variation amplitude ranging within 10.41 ～ 12.75, 8.02～ 9.73, 6.49～ 10.09 g/kg and 7.74 ～12.58 g/kg respectively. The organic matter content began to rise for soil with more than 18 - year alfalfa, and the variation amplitude was 2.69,1.39,1.37 g/kg and 0.97 g/kg in each layer of the soil respectively. The study indicated that alfalfa showed a trend of degradation, the soil water, volumetric weight and organic matter indicated the trend of decline with alfalfa growth ages increasing.