Abstract
It is not often possible to analyze the soil and plant frequently enough to determine their nutrient contents nor is it simple to determine the efficacy of bio-fertilizers in supplying N. Therefore, alternatives needed for frequent prediction of at least one or two elements are described. To some extent, N can be quantified using nitrate reductase activity (NRA) or by chlorophyll index as studied in this investigation. The relationship of NRA, chlorophyll index, and macronutrient content was studied with various levels of N, P, farmyard manure (FYM), and bio-fertilizers in Typic Ustifluvents (saline phase). The nitrate reductase activity, chlorophyll index, N content, and yield of wheat increased with increasing levels of N alone or in combination with P, FYM, and bio-fertilizers. The P content decreased in wheat with application of N and bio-fertilizers and increased with P and FYM. The K content in grain decreased with higher levels of N, P, and bio-fertilizers and increased in straw. Azotobacter proved superior to Azospirillum with respect to yield, N content, NRA, and chlorophyll content. The NRA and chlorophyll contents were directly correlated with grain and straw N content and yield under increased levels of N or with bio-fertilizers. The NRA and chlorophyll index could be used as tools to assess the efficacy of bio-fertilizers at any stage of crop growth without soil analysis and could predict the yield. Based on chlorophyll index values, N contributed by bio-fertilizers was equivalent to 20 kg N ha-1. Yield also confirmed the same level of N availability.
