Effect of application methods of nitrogen biofertilizer on Thompson Seedless grape transplants.

Abstract

A pot experiment was carried out in 2002 and 2003 seasons to study the effect of application methods of biofertilizer (Azotobacter chroococcum) on plant growth, mineral content and microbial activity in the rhizosphere of Thompson Seedless grape transplant. This experiment involved four methods of application of nitrogen biofertilizer (fresh liquid culture of Azotobacter chroococcum). The methods of application were; A=mixing the soil with biofertilizer before transplanting, B=surface application, C=spraying bare roots of transplants with the biofertilizer just before transplanting and D=the control treatment which was treated with tap water only before planting. For all the methods, only one level of biological nitrogen fertilizer (100 ml/plant/year) was added one time at transplanting time in the last week of March in each season. Consequently, the experiment included four treatments in a randomized complete block design. Each treatment was replicated eight times on one plant plots. Generally in the two seasons the unfertilized plants gave the least values of plant growth (shoot length, stem diameter, number of leaves and whole plant fresh & dry weights) while inoculating Azotobacter chroococcum through root application or surface application increased plant growth more than soil application. Regarding leaf mineral content, the unfertilized transplants gave the least values of different nutrients (N, P, K, Fe and Mn) in leaves. However, inoculating A. chroococcum through soil, surface and root applications increased leaf mineral content. However, the promising methods on leaf mineral content were root and surface applications. The microbial activity determinations proved that the methods of root or surface applications increased counts of Azotobacter and CO2 evolution more than soil application while the least values of activity were found in the rhizosphere of unfertilized plants. Therefore, inoculating A. chroococcum through root or surface applications could be recommended as suitable methods of biofertilization of grape transplants.