25Seletividade e eficiência de herbicidas no controle de plantas daninhas na cultura do feijão-caupi Rev A falta de conhecimento sobre herbicidas para o manejo químico das plantas daninhas é uma das principais limitações para a expansão da cultura do feijão-caupi, na região centro-sul do Brasil. Com o objetivo de avaliar a seletividade e a eficiência de herbicidas na cultura do feijão-caupi, foram conduzidos dois experimentos de campo, um com a cultivar BRS Guariba e, outro, com BRS Novaera, em Botucatu-SP. Em ambos os experimentos, o delineamento utilizado foi o de blocos casualizados, em esquema fatorial 3 x 2 + 2, com quatro repetições. Os tratamentos foram constituídos pelas combinações de três herbicidas (bentazona, fomesafem e diclosulam) com duas épocas de aplicação (inicial e tardio), além de uma testemunha capinada e, outra, sem capina. O herbicida diclosulam provocou elevada fitotoxicidade e reduziu a população de plantas, enquanto o bentazona proporcionou os menores níveis de fitointoxicação às duas cultivares de feijão-caupi. O fomesafem, especialmente quando aplicado na fase inicial, foi o mais eficaz no controle das plantas daninhas e, mesmo causando fitotoxicidade à cultura do feijão-caupi, propiciou população de plantas adequada, bem como produtividades de grãos semelhantes às obtidas com a testemunha capinada. Assim, conclui-se que o herbicida fomesafem é o mais eficiente para ambas as cultivares de feijão-caupi. Palavras-chave: Selectivity and efficiency of herbicides in controlling weeds on cowpea cropA lack of knowledge about herbicides for chemical weed control is one of the major difficulties for the expansion of the cowpea crop in the mid-south region of Brazil. Aiming to evaluate the selectivity and efficiency of herbicides for cowpea crop, two field experiments, one of them with BRS Guariba and the other with BRS Novaera, were carried out in Botucatu, São Paulo, Brazil. In both experiments, the experimental design was a randomized block, in a 3 x 2 + 2 factorial scheme, with four replications. The treatments were a combination of three herbicides (bentazon, fomesafen, and diclosulam) and two application times (early and late), besides a weeded control and a non-weeded control. The herbicide diclosulan provided high phytotoxicity and reduced plant population, while bentazon provided the lowest levels of phytointoxication in both cowpea cultivars. The fomesafen, especially when applied in the initial phase, was the most effective in controlling weeds and even causing phytotoxicity to cowpea crop, provided adequate population of plants and grain yield similar to those obtained in the weeded control. Thus, it is concluded that the herbicide fomesafen is the most efficient to both cowpea cultivars.

Nitrogen (N) is the nutrient most required by common bean, and the response to N fertilization may be variable among genotypes. The objective of this work was to evaluate the N nutrition, grain yield, grain size, and crude protein concentration of common bean cultivars in response to topdressing N rates. Two experiments were conducted on a Typic Rodudalf, under two growth conditions ("dry" and "rainy" seasons). A randomized complete block design with a 7 × 4 factorial arrangement and four replicates was used. The treatments consisted of seven cultivars (Pérola, BRS Ametista, BRS Notável, IPR Campos Gerais, IPR Tangará, IAC Formoso, and IAC Imperador) and four N rates (0, 35, 70, and 140 kg ha-1). The experiments were analyzed jointly. The application of N did not affect the cycle, plant population, and number of grains per pod, but increased the leaf N concentration, number of pods per plant, grain size, and grain yield, regardless of the cultivar. The responses of common bean cultivars to N rates varied according to the growth condition, with response to N only in the "rainy" season experiment, under conditions of lower N and higher C/N ratio in the straw of the preceding crop. The crude protein concentration in the grains was influenced in an inconsistent manner by the factors studied.

No abstract