ABSTRACT
ABSTRACT: Nitrogen (N) is the main nutrient responsible for the green coloration of lawns but also stimulates the growth of the aerial portion of grass, thus increasing mowing expenses. Therefore, herbicides may be used as a growth regulator. The ideal herbicide will reduce lawn height without affecting esthetics. Toward this end, the aim of the present study was to evaluate the green coloration of Emerald grass ( Zoysia japonica Steud.) under the effect of different N doses or herbicides used as growth regulators. The study site consisted of randomized blocks containing 20 treatments arranged in a 5×4 factorial design with four treatment groups: four herbicides (glyphosate, imazaquin, imazethapyr, and metsulfuron-methyl, accounting for 200, 420, 80, and 140g ha-1 of the active ingredient, respectively) and the control sample (no herbicide); and three doses of N in the form of urea (5, 10, and 20g m-2), divided into five applications per year, in addition to a treatment without N. Leaf chlorophyll content (LCC) was assessed and the aerial portion of the lawn was measured with digital image analysis. Doses of N ranging from 10 to 20g m-2, divided into five applications a year, provided the lawn with intense green coloration, and the herbicides glyphosate (200g ha-1), imazaquin (420g ha-1), and imazethapyr (80g ha-1) were reported to be suitable for use as growth regulators of the study species, considering maintenance of esthetic quality (green coloration). The digital image analysis of the aerial portion provided more accurate results than use of a chlorophyll meter with regard to the recommendation of both N dose and herbicides to be used as growth regulators of Emerald grass.
RESUMO: Embora o nitrogênio (N) seja o principal nutriente responsável pela coloração verde dos gramados, o mesmo estimula o crescimento da parte aérea, resultando em maior dispêndio com cortes. Assim, a utilização de herbicidas como reguladores de crescimento seria alternativa, sendo ideal aquele que reduzisse a altura sem afetar a estética do gramado. Diante do exposto, objetivou-se avaliar a coloração verde da grama esmeralda ( Zoysia japonica Steud.) sob o efeito de doses de N e do uso de herbicidas como reguladores de crescimento. Utilizou-se o delineamento em blocos casualizados com 20 tratamentos dispostos num fatorial 5x4 com quatro repetições, sendo quatro herbicidas: glyphosate, imazaquin, imazethapyr e metsulfuron-methyl (200, 420, 80 e 140g ha-1 do ingrediente ativo (i.a.), respectivamente) e a testemunha (sem herbicida); e três doses de N na forma de ureia: 5, 10 e 20g m-2, parceladas em cinco aplicações ao ano, além do tratamento sem N. Avaliaram-se o índice de clorofila foliar (ICF) e a análise por imagem digital da parte aérea do gramado. Doses de 10 a 20g m-2 de N, parceladas em cinco vezes ao ano, propiciaram coloração verde intensa do gramado e os herbicidas glyphosate (200g ha-1), imazaquin (420g ha-1) e imazethapyr (80g ha-1) foram adequados para utilização como reguladores do crescimento da espécie estudada, considerando a qualidade estética (cor verde). A análise por imagem digital da parte aérea forneceu resultados mais precisos que o uso do clorofilômetro, quanto à recomendação da dose de N, bem como dos herbicidas a serem utilizados como reguladores de crescimento da grama esmeralda.
ABSTRACT
Laboratory experiments were conducted to evaluate adsorption, desorption and mobility of metsulfuron-methyl in soils of the oil palm agroecosystem consisting of the Bernam, Selangor, Rengam and Bongor soil series. The lowest adsorption of metsulfuron-methyl occurred in the Bongor soil (0.366 ml g-1), and the highest in the Bernam soil (2.837 ml g-1). The Kfads (Freundlich) values of metsulfuron-methyl were 0.366, 0.560, 1.570 and 2.837 ml g-1 in Bongor, Rengam, Selangor and Bernam soil, respectively. The highest K fdes value of metsulfuron-methyl, observed in the Bernam soil, was 2.563 indicating low desorption 0.280 (relatively strong retention). In contrast, the lowest Kfdes value of 0.564 was observed for the Bongor soil, which had the lowest organic matter (1.43%) and clay content (13.2%). Soil organic matter and clay content were the main factors affecting the adsorption of metsulfuron-methyl. The results of the soil column leaching studies suggested that metsulfuron-methyl has a moderate potential for mobility in the Bernam and Bongor soil series with 19.3% and 39%, respectively for rainfall at 200 mm. However, since metsulfuron-methyl is applied at a very low rate (the maximum field application rate used was 30 g ha-1) and is susceptible to biodegradation, the potential for ground water contamination is low.