BIO-INOCULATION AND Zn APPLICATION AS AN ALTERNATIVE STRATEGY OF PARTIAL N-MINERAL NEEDS FOR ALLEVIATING THE POSSIBLE CHEMICAL POLLUTION OF SOME CEREAL CROPS

Abstract

This work is an important strategy for understanding the local best usageof either N-mineral or N-bio-sources, whether be under demand for agriculturalutilization projects. Also, it represents a huge challenge and technical solutionfor alleviating the possible adverse fears of human health throughenvironmental risks as a result of excessive use of the nitrogenous chemicalfertilizers for fertilizing some cereal crops as well as to support the newlytechnique of “clean, bio- and organic agriculture”.So, a field experiment was conducted on a clayey soil during twosuccessive seasons of 2008-2009 and 2009-2010 at Damas village, Mit Ghamerdistrict, El-Dakahlia Governorate, Egypt, to identify the outcome of replacing25 % from the recommended N-mineral dose (RND) of wheat crop by using abio-inoculation with Paenibacillus polymyxa bacteria under different rates ofZn-EDTA (i.e., 0, 1.0, 1.5 and 2.0 kg fed-1 as soil application) on wheat(Triticum aestivum L., Sakha 93 cv.) vegetative growth as well as harvestcrop parameters, i.e., spike characters, weight of 1000 grain, grain and strawyields/fed & their nutrient contents of N, P, K, Fe, Mn, Zn and Cu. Soil contentof available nitrogen forms (NH4+ and NO3-) as related to nitrogenase enzyme inthe soil after 70 days from sowing was taken into consideration in this study.The obtained data show that grain bio-inoculation and Zn-chelate applied,as shown in the treatment (Paenibacillus polymyxa bacteria + 75 % RND +highest Zn rate of 2 kg/fed), led to an almost similar plant vegetativeparameters (i.e., plant height, No. of tillers plant-1, dry weight plant-1, leafchlorophyll a & b and carotenoids) to those received the full recommended Nmineral dose. However, the relative decrease percentages in such parameterswere negotiable, insignificant and not exceeding 3 %. The reverse was true foravailable nitrogen forms (NH4+ and NO3-), mainly due to the pronouncedincrease in nitrogenase activity. The corresponding relative increase percentagein N-forms recorded 18.77 and 8.51 % over the soil treated with 100 % RND,respectively. That was true, since such increases were more closely attributed toan achieved increase (53.04 %) in the nitrogenase activity of plant rhizosphere.A similar way and a parallel trend for the growth parameters wereobserved with wheat spike characters (i.e., weight plant-1 and number plant-1),harvest crop parameters (i.e., grain weight plant-1, straw weight plant-1, weightof 1000 grain, grain and straw yields fed-1), grain and straw contents of N, K,Fe, Mn, Zn, and Cu. However, the obtained values of these plant parameterswere achieved negotiable and insignificant differences don't exceeding 2 % atthe treatment of (bio-inoculation + 75 % RND + highest Zn-chelated rate of 2kg/fed) as compared to those treated with full recommended N-dose.So, it could be said that the integrated combination between N-biofixation and applied soil Zn-chelated leading to a continuous bio-fixednitrogen slow release along the growth stages of wheat plants, to minimize its possible lose by either leaching process or volatilization, and in turn torationalize use of N-mineral fertilizers, which is surplus point for sustainableagriculture system. Such system represents a new agriculture strategy thataffects the country's economy and its development. That is due to the possibleadverse fears on either crop products or human health should be alleviated,besides it represents an ideal solution to meet the excessive nitrogenousfertilizers demand.