Nodulation characteristics, nodule nitrogen, and carbon dioxide fixation in pigeon pea as affected by nitrogen

Bhupinder Singh and Binod Kumar Singh

International Journal of Vegetable Science, 17: 274–282, 2011

Abstract

The legume pigeon pea [Cajanus cajan (L.) Millsp.] is an important rainfed crop in many areas of the world. Production can be reduced when high nitrogen is present and symbiotic activity is low. A field experiment was conducted to determine the effects of nitrogen rate on nodulation, nodule carbon, and nitrogen fixation in 40 pigeon pea genotypes. Nitrogen was applied as urea at 40 (N40) and 120 kg·ha−1 of N (N120). Shoot biomass, root nodulation, amounts of nitrogen and carbon fixed, nitrate reductase activity in roots and nodules, and nitrite content in roots and nodules were determined. Genotype, N rate, and the interaction affected results. The genotypes Pusa-2001 and Sel-90306-11-4 had the most nodule mass at N40. Nitrogen rate did not affect nodule nitrogen-fixing effectiveness. Genotype Pusa-2001 had higher biomass at N120. Genotype Sel-90306-11-4 had high phosphoenol pyruvate carboxylase activity even at

N120; which likely reduces host carbon dependence for nodule nitrogen function and improves carbon diversion to the reproductive sink. At N40 ‘Sel-24’ formed large nodules with effective nitrogen fixation, which was impaired at N120. ‘RG-01-69N’ had lower numbers of nodules, nodule mass, and nitrogen fixation but more shoot biomass than the majority of the pigeon pea lines. N-response of pigeon pea was evident for nodule N2 fixation. Genotypes with improved nodule CO2 fixation may lead to increased yield and quality in monocropped and intercropped pigeon pea.

Key words: Cajanus cajan, Nitrate reductase, Nitrogenase activity, Phosphoenol pyruvate

carboxylase activity, India.