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To obtain high yields of winter wheat, it is important to control the contamination of crops with weeds. It is known that yield losses can be 30% or more due to the presence of segetal vegetation in wheat crops. With intensive technology of growing winter wheat, the chemical method of protection against weeds is an extremely important element. The paper highlights data on the species composition and class of contamination of winter wheat agrocenosis. The effectiveness of herbicides and their tank mixtures in winter wheat crops to reduce the presence of the weed component, increase grain yield and quality in the conditions of Luginsky District of Zhytomyr region on sandy loam soils during 2019-2021 was studied. It is established that the structure of the weed component of agrophytocenosis of winter wheat in farm conditions is dominated by dicotyledonous weed species, namely: field mustard (Sinapis arvensis L.), wild radish (Raphanus raphanistrum L.), wild pansy (Viola tricolor L.), shovelweed (Capsella bursa-pastoris L.), toadpipe (Equisetum arvense L.), and blue bottle flower (Centaurea cyanus L.), the share of which is 64.8%. Graminaceous species of weeds are represented by silky bent grass (Apera spica-venti L.), couch-grass (Elytrigia repens L.), rye brome grass (Bromus secalinus L.). The technical efficiency of the studied herbicides with the separate and joint application was in the range of 60.8-94.6%. The highest indicator of technical efficiency of herbicides in winter wheat crops, which is 94.6%, was obtained in an experiment using a tank mixture of Granstar Pro 75 + Apiros 75 preparations, with norms of 0.025+0.013 kg/ha, as well as an increase in wheat grain yield by 2.0 t/ha compared to the contaminated control. Spraying winter wheat crops with herbicides during the growing season allows improving the quality indicators of the grain yield structure. In particular, the content of protein and fibrin increases by 1.1 times; the moisture content of grain decreases by 1.0-1.1 times, and the content of dirt impurity decreases by 2.8-6.7 times, compared to the control version

O teor de N mineral do solo não é usado na recomendação de adubação nitrogenada para cultivos de grãos no Brasil, devido à sua elevada instabilidade por efeito dos fatores ambientais. Seu uso poderia melhorar a eficiência das adubações e reduzir os custos de produção. Foi feita uma análise dos teores de NH4+ e de NO3- do solo, até 15 cm de profundidade, no período da pré-semeadura e do rendimento de grãos em 61 ensaios de cevada, em 20 municípios, em três Regiões Fisiográficas do Rio Grande do Sul, de 2002 a 2005. Os rendimentos foram divididos em classes (muito baixo, baixo, médio, alto e muito alto), que foram relacionadas aos teores de N mineral, usando o modelo de regressão de Gompertz. O ajuste indicou dois marcos de N mineral delimitadores do rendimento relativo: 8 e 18 mg kg-1 de N no solo. Abaixo de 8 mg kg-1 de N houve predomínio de muito baixos rendimentos, evidenciando o efeito da baixa disponibilidade sobre a produtividade. Acima de 18 mg kg-1 de N, este nutriente não foi mais fator decisivo na formação do potencial produtivo, sendo indicativo de potencial produtivo muito alto. Esses valores poderão futuramente ser incorporados como base de um modelo de recomendação de adubação nitrogenada.Soil N mineral content is not considered when recommending N for grain crops in southern Brazil due to the high variation according to environmental conditions. In the methodology described here soil N mineral is considered in adjusted N recommendations to increase efficiency and reduce production costs. The soil levels of NH4+ and NO3- were analyzed to a depth of 15 cm, in the pre-sowing and grain yield stage of 61 barley trials distributed in 20 counties in three regions of Rio Grande do Sul State (Depressão Central, Planalto Médio and Alto Uruguai) for four years (2002-2005). The yield potential was classified (very low, low, medium, high and very high) and related to the N mineral contents using the Gompertz regression model. The adjusted model indicated two N mineral values delimiting relative yields: 8 and 18 mg kg-1 soil. Low yields predominate below 8 mg kg-1 soil, indicating a direct effect of low N availability on yield potential very early in the season. At soil NH4+ and NO3- values over 18 mg kg-1 soil N was no longer decisive in the formation of yield, indicating a very high yield potential. These values may be useful in models of N recommendation.