Forage Production, Nitrogen Fixation, and Soil N Accumulation of White Clover in the Hill Farming System of Azad Jammu and Kashmir.

摘要

Quantitative measurements of plant growth characteristics, forage production, nitrogen (N) fixation, and soil N accumulation by white clover were determined in a field experiment at the subhumid hilly region of Rawalakot, Azad Jammu and Kashmir (AJK). Three indigenous and two exotic ecotypes of white clover were used in the study. Indigenous ecotypes were collected from three different locations (i.e., Tollipir, Banjosa, and Rawalakot), whereas exotic ecotypes (NuSiral and Irrigation) were collected from New South Wales Agricultural Research and Advisory Station, Australia. Data were collected for two seasons (spring 2004-autumn 2004). Total average values for height, number of stolons, length of stolons, number of leaves, and leaf area were 13-50 cm, 9-20, 2-4 cm, 23-81, and 7-16 cm2, respectively. The morphological characteristics of exotic ecotypes were significantly higher than the indigenous ecotypes, and the percentage increase in different plant characteristics was +6% to 214%. Total herbage dry-matter yield (DMY) in the indigenous and exotic ecotypes varied between 0.5-2.3 and 3.6-4 Mg ha-1, respectively. All the ecotypes showed substantial nodulation potential, and the number of nodules in plant roots ranged from 65 to 119, confirming the presence of indigenous Rhizobium population in the soil. The N contents of harvested herbage of white clover were 2.3-3.0% compared to 0.85% in the grass, and the estimated rates of N2 fixation were 26 kg N ha-1 in the indigenous to 79 kg N ha-1 in the exotic ecotypes. Amount of N2 fixed was strongly correlated with DMY, suggesting that crop DM can be used as an indicator of N2 fixation in white clover. Protein content of white clover was 14-19%, compared to 5% in the indigenous grass species. Total organic carbon (C) and N in control soil were 8.5 and 0.75 g kg-1, which increased significantly to 13.1 and 0.93 g kg-1 in soil under white clover. It is concluded that white clover has substantial potential for growth and establishment in the subhumid hilly regions and can be used to recuperate degraded soils because of its ability to sustain high level of pasture production and increase the N status of soil. These benefits could be of particular use for small-scale resource-poor farmers.