EFFECT OF DIFFERENT INOCULANTS ON THE DISTRIBUTION OF NUTRIENTS IN PLANT BODY AND ASSOCIATED RHIZOSPHERE

Abstract

Wheat is the most important staple diet of the people of Pakistan. It contributing 13.7 percent to the value added in agriculture and 3.0 percent to GDP. Pakistan is world’s 8th largest wheat producer with a total production of 23.47 million tons. Among the leafy vegetables, spinach is an important source of nutrients in the diet ranking 2nd after kale in total carotenoids and folate. It is also a rich source of vitamin A, vitamin C, vitamin E, vitamin K, magnesium, manganese, betaine, iron, vitamin B2, calcium, potassium, vitamin B6, folic acid, copper, protein, phosphorus, zinc, niacin, selenium and omega-3 fatty acids. Pakistan is world’s 9th largest spinach producer with 95.5 thousand tons annual production having 1.2 tons h-1 yield. Fertilizer applications significantly enhance growth, yield and nutrient uptake traits of cereal and non-cereal crops. The hazardous environmental consequences and high cost of inorganic fertilizers make them not only undesirable but also uneconomical and out of reach of the small farmers, which needs to be replaced with the natural organic fertilizers for reducing health hazards and prevent environmental degradation. Present research undertaken was an endeavour to studying the role of soil applied microorganisms and crop productivity of wheat and spinach. Nitrogen and phosphorus are the major limiting factor in agricultural soils of Pakistan. Biofertilizers are considered to be the only supplement fertilizer to minimize use of chemical fertilizers, which apart from their increasing cost are enhancing the pollution hazards of our environment. The plant growth promoting rhizobacteria (PGPR) and phosphorus solubilizing microorganisms (PSM) are important because they help in plant growth and development. Bioinoculants have multiple modes of operations. They not only fix atmospheric N, or solubilize soil phosphorus but may act through hormones production. In this study Humic Acid and IAA are used as non-biological control treatments, in addition to urea and singal super phosphate (SSP) to compare the performance of bioinoculants in terms of hormonal mode of action in addition to their N-fixing, phosphorus solublizing and xxix zinc solublizing abilities. Assessing the capacity of these microorganisms to be used as a consortium in biofertilizer for wheat and spinach was the main objective of this investigation. The present study was to strengthen such endeavors and to provide a better combination for nutritional requirements of these important crops. This research work was categorized into eight treatments in wheat crop and ten treatments in spinach crop. The PGPR and PSM used were selected isolates from Soil Biology repository, NARC, isolated from rhizosphere, rhizoplane and roots of wheat and spinach on their respective media. Two sets of microorganisms were used for the two test crops. The inoculants were applied as seed treatments. Plants above ground and below ground parts and rhizosphere samples were collected at various stages of growth and development for the analysis of N, P, K, Fe and Zn in both wheat and spinach crop. Microbial analysis of the rhizosphere was carried out at three stages of growth to check the viability of microorganism in plants rhizosphere, an important pre-requisite for beneficial effects on plants. Enumeration of microbes was carried out on p-free medium, Sodium Lactate medium, N-free and Yeast Manitol medium. Statistical analysis of the results shows that all treatments differed significantly from each other in all indices of growth. The maximum increase in wheat shoot dry biomass, straw biomass, maximum number of tillers, highest root dry biomass of wheat was recorded with Humic Acid and Rhizobium + ½ NP as compared to the application of chemical fertilizers alone. Application of Humic Acid and Rhizobium + ½ NP increased the uptake of nitrogen, phosphorus and potassium as compared with chemical fertilizers alone at different stages. Maximum iron content was recorded with Rhizobium + ½ NP, Pseudomonas+ N ½ P and HA. Maximum zinc content of wheat crop was recorded with the application of Rhizobium+ ½ NP, Pseudomonas+ N ½ P and Azospirillum+ ½ NP as compare to the application of chemical fertilizers alone. Application of Azorhizobium + ½ NP, Rhizobium + ½ NP, Pseudomonas+ N ½ P and Azospirillum+½ NP saved the rhizosphere N upto 73%, phosphorus 74%, potassium 12.4%, iron 18% and zinc 62% respectively. Analysis of the data concluded that application of Rhizobium+ ½ NP as well as HA increased grain yield of wheat upto 43% as compared to the recommended dose of the application of chemical fertilizers alone. In case of spinach, it is concluded from the statistical analysis of results that biological inoculants significantly affect the growth, N, P, K, Fe and Zn uptake. The maximum foliage dry biomass of spinach shoot and root was recorded with Azorhizobium and Rhizobium as compared to the uninoculated control. Highest spinach nitrogen, phosphorus and potassium accumulation in foliage was recorded with Azorhizobium, Rhizobium and PSM-QA as compared to uninoculated control at different stages of growth. Maximum quantity of iron and zinc uptake in spinach was recorded with Azorhizobium, Rhizobium, Tax-psm1 and PSM-QA as compared to uninoculated control at different stages of growth. Maximum soil nitrogen content of spinach rhizosphere was recorded with NP as compared with uninoculated control. Maximum spinach rhizosphere phosphorus content was recorded with ½ NP, SP.OL and NP as compared with uninoculated control at different stages. Maximum rhizosphere potassium content was recorded with PSM-QA and ½ NP Azorhizobium and Rhizobiumat different stages as compared with uninoculated control. Highest rhizosphere iron and zinc content was recorded with the application of Azorhizobium, Rhizobium, SP.OL, PSM-QA and Taxpsm1 at different stages as compared with uninoculated control. It can thus be concluded that application of bacterial isolates inhanced not only the nutrient uptake in both the crops but enhanced the concentration of nutrients in the rhizosphere of both the crops, whereas humic acid proved very effective in the nutrients uptake of wheat crop. It is recommended that further experiments related to inoculation of beneficial microorganisms should be carried out to firm up the conclusions and formulate technology packages for reducing the deleterious effects of chemical fertilizers and safeguarding the natural environment for sustainable crop production.