Research Journal of Agricultural Science, 44 (3), 2012 30 INFLUENCE OF NPK FERTILIZERS UPON WINTER WHEAT GRAIN QUALITY Florin CRISTA 1 , Isidora RADULOV 1 , Florin SALA 1 , Laura CRISTA 2 , Adina BERBECEA 1 1 Banat’s University of Agricultural Sciences and Veterinary Medicine, Faculty of Agricultural Sciences, Timisoara, Aradului Street, no. 119, RO-300645, Romania 2 University Dimitrie Cantemir,Faculty of Tourist and Commercial Management Timisoara E-mail:florincrista@yahoo.com Abstract: The most efficient way of improving food resources of humanity is to increase agricultural production per hectare in arable terrains by introducing new varieties and qualified hybrids and by improving crop technology. Wheat contains a large quantity of starch (65 – 70 %), the main component of grain, and also, some sugars (maltose, sucrose). All these have an important energetic role. The wheat contain almost the entire types of amino acids, nevertheless lysine, methionine, threonine and tyrosine are find in insufficient quantities for human requirement. The research takes place in experimental field from U.S.A.M.V.B. Didactic Station from Timisoara and after that in the research lab of Soil Science and Plant Nutrition Department from Agricultural Faculty. The experiments are stationary type, with wheat – maize – sun flower rotation. Each plot is sub-dived in four repetitions, linear, with size of 10 x 3 m (30 m 2 ). The variety used for this experiment is Alex variety. The fertilizers used are: 20.20.0 complex mineral fertilizers, N 28 liquid foliar fertilizers Nitrophoska 13.42.0 micro granulated fertilizers. Raw protein content from wheat grain was determined by Kjeldahl method, as Kjeldahl nitrogen multiplied with 6.25. The amino acids were assayed using ion-exchange chromatography after hydrolizing with 6 M HCl for 24h at 110ｰC. Methionine and cystine were analyzed by using formic acid protection prior to acid hydrolysis. The higher values for raw protein were founded in the case of maximum dose of nitrogen fertilizers. The increase of phosphorus and potash fertilizers doses influence in an insignificant manner the nitrogen content of grains. The raw protein content from wheat grain is significant in the case of fertilized wheat; the lowest content in raw protein was found in the case of unfertilized wheat. The increase of mineral fertilizers dose has a major role in the variation of histidine content. The content of isoleucine depend in a less important manner by the fertilizers doses. The arginine content from wheat grain is found in connection with fertiliser dose. The metionine content from wheat grain is undersized; the use of mineral fertilizers has an insignificant impact. Key words: fertilization, wheat, raw protein, amino acids INTRODUCTION Amino acid composition is an important feature in determining the nutritional value of wheat grain for human and animal diets. From all agricultural crops, wheat represents the most important cultivated species. The wheat contain almost the entire types of amino acids, nevertheless lysine, methionine, threonine and tyrosine are find in insufficient quantities for human requirement. Wheat contains a large quantity of starch (65 – 70 %), the main component of grain, and also, some sugars (maltose, sucrose). All these have an important energetic role. Nitrogen fertilizer whether applied to the soil (DUBETZ, 1972; FAJERSON, 1961; SOLSULSKI et al., 1963) or to the plant (FINNEY et al., 1957; KOLDERUP, 1974) can be used in to increase the protein content of wheat (Triticum aestivum L.) and changes in amino acid composition are associated with increased grain protein. The grain protein content and amino acid composition of wheat also vary genotype and environment, including rate and time of nitrogen fertilization, water availability and