Springer Online Journal Archives 1860-2000
Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
Abstract Guar (Cyamopsis tetregonoloba (L.) may be grown when soil temperatures are potentially high enough at the time of planting to inhibit nodulation and N2 fixation. An experiment was conducted using controlled conditions to determine the influence of high root temperature on growth and N2 fixation of guar. The experiment included two strains of rhizobia, two varieties of guar, two mineral N treatments, and root temperatures of 34, 37, and 40°C. Plants were grown for 44 days. The root temperature of 40°C reduced N fixation by at least 80% and nodule weight by more than 50%. Significant interactions occurred between most factors in influencing nodulation, N2 fixation and dry matter production. Guar, nodulated by rhizobial strain GAR022-1 and fully dependent on N2 fixation or provided with starter mineral N (25 mg pot−1), was not influenced by the root temperature of 37°C as compared to 34°C. Nodulation and N2 fixation by strain 32H1 was reduced by at least 40% when no starter mineral N was provided and the root temperature was 37°C. Providing starter mineral N to one variety of guar doubled the quantity of N2 fixed by strain 32H1 at both 34 and 37°C but N2 fixation was lower at the higher root temperature. It appears that root temperatures between 37° and 40°C bracketed the critical root temperature for N2 fixation by nodulated guar and that the critical root temperature for guar dependent on mineral N was above 40°C.
Type of Medium: