Rhizobium inoculation and nutrient levels on nodulation and seedling growth in tree legumes

Abstract

An investigation entitled Rhizobium inoculation and nutrient levels on nodulation and seedling growth in tree legumes was carried out at College of Agriculture, Vellayani during August 1990 to July 1991. The investigation was carried out as three separate experiments. The main objective of Experiment I was to determine the effect of different scarification methods on the germination of some commonly grown and newly introduced legumes, the objective of Experiment II was to screen out the best among the native and exotic isolates of Rhizobium with different levels of phosphorus on the nodulation and seedling growth and the objective of Experiment III was to study the effect of Rhizobium inoculation, and nutrient levels on nodulation and seedling growth of tree legumes. The experiment (s) were carried out in a completely randomized design with five, three and four replications each for Experiments l, ll and lll respectively. Hot water treatment for three minutes was found to be effective for enhancing the germination in Acacia mangium, Paraserianthes falcataria and Sesbania grandiflora. Treatment with Con.Hcl for one minute recorded highest germination per cent in Cassia fistula. Germination percentage of 98.27 was recorded with Con.HNO3 treatment for 10 inutes. In Acaci’s Acacia Catechu and Cassia javanica maximum germination was obtained with Con.H2 SO4 treatment for five minutes, while that for one minute resulted in highest germination in Albizia moluccana. Exotic isolates, TAL 1868 and TAL 45 wire proved to be the best among the rhizobial isolates for Acacia and Albizia sp. Respectively with respect to growth and nodulation characterstics as compared to the local strains. Plant height, shoot dry weight and root dry weight were significantly influenced by phosphorus application. Nodule number per plant had increased from 0.67 to 1.33 in Acacia Arabica. Nitrogen application along with inoculation significantly influenced growth characters such as plant height, shoot dry weight and root dry weight. Maximum plant height was recorded due to application of nitrogen upto 20 kg ha-1 in Acacia Arabica and Acacia Catechu. Nitrogen application upto 20 kg ha-1resulted in highest shoot dry weight and root dry weight in both Acacia Catechu and Paraserianthes falcataria. Application of nitrogen did not increase nodule number per plant in all the tree species. However, nodule dry weight per plant increased with application of nitrogen up to 20 kg ha-1. Phosphorus application up to 50 kg ha-1 produced maximum shoot and root dry weights in Acacia catechu. Application of Phosphorus at 25 kg ha-1 resulted in maximum root dry weight in Acacia Arabica and Acacia catechu. Phosphorus application up to 25 kg ha-1 resulted in maximum number of nodules per plant in Acacia Arabica and acacia catechu. Highest nodules dry weight per plant was recorded with phosphorus application up to 25 kg ha-1 in Acacia catechu and Paraserianthes falcataria. Nitrogen application upto 20 kg ha -1 resulted in an increase in plant nitrogen content and reduction thereafter. Phosphorus application upto 25 kg ha -1. Resulted in an increase nitrogen content of plants and a reduction was noticed beyond 25 kg ha-1. Nitrogen application had significant influence on phosphorus content of plants in A Arabica and P. falcataria. Phosphorus application at 50 kg ha-1 gave highest phosphorus content in A. Arabica and A. catechu. It can be concluded that nitrogen and phosphorus application along with Rhizobium inoculation using specific strains is essential for better growth and nodulation of leguminous tree species.