Deterioration of Alfalfa Swards in the Hot Humid Subtropics of India 1

Alfalfa ( Medicago sativa L.) planted in the humid subtropics of India has not persisted well. To determine the effects of management practices on persistence and production, herbage growth, plant populations, Fusarium incidence on roots, and total available carbohydrates (TAC) were determined. Seven P and K fertilizer regimes and two cutting frequencies were used with ‘Anand—2’ and ‘Sirsa‐9’ alfalfa cultivars sown in the fall of 1975, 1976,. and 1977 on an Antisol soil in the subtropical plains of the eastern region in India. In 1976‐1977 and in 1977‐1978, Sirsa—9 yielded 7.6 and 9.7 metric tons/ha, respectively, while Anand—2 produced 6.9 and 8.3 metric tons/ha, of dry matter, respectively. Major fertilizer yield response was almost linear for 0, 22, and 44 kgha of P. Response to K was minimal and only after plant P needs were satisfied. Response to P was greater in 1977‐1978, Plant populations decreased consistently during the summer to about zero in October 1976 and August 1977, while in 1978 in a better drained area plant populations in July reduced from 70 to 30%. Root weights decreased drastically from 172 days after sowing (DAS) to 263 DAS regardless of management factor in the first two seasons. Fusarium root rot incidence by 203 DAS was severe for all management treatments except for one K treatment. No relationship between incidence and herbage yield was evident, however. Plant density and disease seventy was positively correlated (r = 0.97). Total available carbohydrate concentrations decreased, also, from about 35 at 172 DAS to 18% at 263 DAS. A positive correlation of r = 0.74 was found between disease severity and TAC. Additional work is needed to delineate the effects of Fusarium , and soil and plant factors before alfalfa could be recommended as a perennial in the subtropical regions representative of the experimental area.