Ways of increasing of nitrogen fertilizer use efficiency on cotton in the belt with irrigated sierozem soils
Subject of the inquiry: An old irrigated typical sierozem soil, an irrigated meadow alluvial soil, cotton crop, labeled and non-labeled nitrogen fertilizer, manure, furrow irrigation, drip irrigation, polyethylene film, mulch.
Aim of the inquiry: Regulation of transformation processes of soil and fertilizer nitrogen in accordance with requirements of cotton plant in the belt of irrigated sierozem soils.
Method of inquiry: Field, lyzimeter and pot experiments with cotton were conducted in accordance with “Methods of field experimentation with irrigated cotton” (Uzbekistan Cotton Growing Research Institute, 1973, 1981). Chemical analyses of soil and plant samples were performed according to "Methods of agrochemical analyses of soil and plants" (Uzbekistan Cotton Growing Research Institute, 1963, 1977). Relative growth rate of cotton stem and dry mass accumulation were determined as suggested by D. 13. South (1991). Relative growth rate of nitrogen productivity was calculated according to P. Poorter (1989). Data were subjected to analysis of variance using PROC GLM procedures in SAS (SAS Institute, 2003).
The results achieved and their novelty: The qualitative data on soil nitrate content as well as the N-total concentrations in cotton leaves allowed for the differentiation and thus improvement of the nitrogen fertilizer application norms and timing for cotton growth.
Fertilizer nitrogen recovery in cotton was determined by l?N methods both for cotton grown with a mulch of polyethylene film and combined with various timings of nitrogen application, different nitrogen quantities and under different irrigation modes including drip and furrow irrigation.
The impact of nitrogen quantities applied during planting on the germination of cotton seeds and stand establishment was researched. The content and dynamic of all soil mineral nitrogen forms were investigated. In addition, estimated was the quantitative ratio of available soil NPK throughout the cotton vegetation period, the relative growth rate of nitrogen productivity, cotton growth and development, and cotton yield depending of the nitrogen application timing while cotton was grown w ith the use of polyethylene film.
Mineralization and immobilization processes of nitrogen in the soil and the fertilizer nitrogen l5N balance was investigated under various ratios of manure carbon and with different brands of fertilizer nitrogen. Results showed that the optimal C:N ratio was obtained with the combination of cow-dung carbon + nitrogen of mineral fertilizer + manure applied, which was reflected in an improved availability of plants nutrients content in the soil, which in turn increased cotton yield and the quality of the cotton lint.
The transformation of mineral forms of soil nitrogen, NPK uptake and dry mass accumulation by plants, as well as cotton yield quantities and quality were investigated subject to various nitrogen rates and application timing combined with different irrigation technologies, irrigation methods and modes.
Practical value: Based on the results following implications options could be elaborated:
- A method for a refined use of nitrogen fertilizers application both in terms of quantities and timing on cotton which is based on the nitrate content in the soil (for automorphyc soils only) and on the nitrogen concentration in plant leaves which is applicable for all soil types;
- nitrogen fertilizer application methods for various irrigation technologies used in cotton production (alternate irrigation during whole vegetation);
- efficient method of a combined application of nitrogen fertilizer and manure on cotton, which lowered the use of nitrogen fertilizer rate by 30% and concurrently increased the scope of usage for organic fertilizer;
- nitrogen fertilizer application timing on cotton when cotton is grown with the use of polyethylene film.
Degree of embed and economic efficiency: The results of the investigations formed the scientific basis for the development of “Practical recommendations in agriculture: soil, water, fertilizer” (in Russian, MAWR, Tashkent, 1996. - 108 p.), “Recommendations on production of high and qualitative cotton yield in Tashkent Province” (in Uzbek, UzSPCA, Tashkent, 1996. - 16 p.), Recommendations on the use of mineral and organic fertilizer in cotton growing” (in Uzbek, UzSPCA, Tashkent, 2003. - 24 p.). Practical recommendations as presented in this thesis were included in various provinces of the country but on a total area of 80,000 hectares. Hence this would lead to a net profit varying from 48,826 to 215,981 sums ha'1 caused by the recommendations
Sphere of usage: Farmers units specialized in cotton production in the belt of the irrigated sierozem soils.