Nitrogen fixation and growth of one-year stands of non-dormant alfalfa in Manitoba

Abstract

Nitro is a non-dormant, special purpose alfalfa (Medicago sativa L.) developed in Minnesota for use as a 1-yr hay source and fall plow-down green-manure crop. Field experiments were established at two Manitoba sites to examine growth and N2 fixation characteristics of Nitro. Nitro was compared with two dormant alfalfa cultivars in 1991, and with three dormant cultivars and another non-dormant cultivar in 1992. Dinitrogen fixation was measured using the 15N isotope dilution technique. Nitro yielded similarly to the other cultivars at the summer hay harvests, but produced significantly more herbage for soil incorporation in the fall relative to the dormant alfalfa cultivars (25% average increase in 1991, 39% increase in 1992). The quantities of N2 fixed were also similar among cultivars at the hay harvests, but were greater in Nitro in the fall relative to the dormant cultivars. Nitro and the dormant cultivars added an average 121.4 and 39.7 kg ha−1 of fixed N to the soil in the fall of 1992, respectively. Nitro was not significantly different from CUF 101, the other non-dormant cultivar tested in 1992, in any of the measured parameters. Over-winter survivability of the non-dormant cultivars ranged from 2 to 62% over the 2 yr. Nitro seems to have an advantage over the traditionally used dormant alfalfa cultivars as a 1-yr hay and fall N source, although further testing is required to determine it's superiority over other non-dormant alfalfa cultivars. Key words: Alfalfa, dormant, Nitro, nitrogen fixation, non-dormant, crop rotations, yield