Production and nutrition of irrigated Tanzania guinea grass in response to nitrogen fertilization

Abstract

-The objective of this study was to evaluate the effects of nitrogen (N) fertilization in the four seasons of the year on forage production, nitrate (NO 3 ) in the sap, total N in the forage and relative chlorophyll index (SPAD reading) in the leaves of irrigated Panicum maximum cv. Tanzania grass, establishing their critical ranges. In addition, we evaluated the ability to predict forage production based on NO 3 in the sap, total N in the forage and relative chlorophyll index. The soil in the experimental area was classified as an Oxisol (Red-Yellow Latosol) with a clayey texture. Annual rates of N (0, 200, 400 and 800 kg ha -1 ) in the form of urea were the treatments tested. Irrigation was performed through a conventional spray system. The NO 3 content in the sap and the relative chlorophyll index were measured in leaves using a portable meter with NO 3 selective electrode and the SPAD-502 portable chlorophyll meter device, respectively. Tanzania guinea grass was very responsive to N fertilization, except in the winter. The critical ranges of the SPAD reading proved to be more adequate for monitoring the nutritional state of N of Tanzania guinea grass in the different seasons of the year than the NO 3 content in the sap and the total N content in the dry matter. Use of the chlorophyll meter is more advantageous than the use of the portable meter with an nitrate selective electrode for predicting the nutritional status of Tanzania guinea grass.

Nutritional characteristics of marandu grass (Brachiaria brizantha cv. marandu) subjected to inoculation with associative diazotrophic bacteria

“…Viana et al (2014) of nitrogen, respectively, and according to Maranhão et al (2009), the chlorophyll content, in addition to indirectly measuring the nitrogen status of plants, may also be used as an indicator of the crude protein content of marandu grass. In the interaction of the cuts within each treatment, the highest values for chlorophyll index were observed in the first cut in all treatments.…”

Guiding fall fertilization of cool‐season turfgrass lawns with verdure tissue‐N tests

“…Optimum sap NO 3 -N concentrations have been reported for annual cereal grasses used for forage as <225 to <440 mg L -1 , depending on species (Westcott et al, 1998;Zhang et al, 1999), and <250 to <325 mg L -1 for different varieties of perennial or short-lived forage grasses (Lyons et al, 1992 (Viana et al, 2014). Although maximizing yields is not a goal for turfgrasses, sap NO 3 -N concentrations correlated to grass growth suggest that this relationship can be used to calibrate N fertilization recommendations.…”

Potencial de resposta ao nitrogênio em pastos manejados intensivamente

“…Contudo, já foram relatadas áreas responsivas para a lavoura de cana de açúcar mesmo com índices de ISNT maiores que 228 mg kg -1 no solo (PEREIRA, 2015). Quanto maior o teor de N aminoaçúcar no solo menor seria a resposta da planta à adubação nitrogenada, porém alguns autores também não encontraram boa correlação entre o ISNT e a resposta da planta (LABOSKI et al, 2008 (CAMPANA, 2008;VIANA et al, 2014).…”

“…Os valores encontrados estão de acordo com a literatura (EUCLIDES e MEDEIROS, 2003;FRANÇA et al, 2007;SÁ et al, 2010 por ano (OLIVEIRA et al, 2009;VIANA et al, 2014). Observou-se através dos teores de proteína bruta associados com as produtividades das pastagens, que o suprimento de N presente no solo atendeu a demanda da forrageira (SHARIFI et al, 2011), mesmo o gênero Panicum sendo classificado como uma gramínea de alta exigência (WERNER et al, 1996).…”

“…Neste experimento, a resposta comportamental para o acréscimo nas doses nitrogenadas foi similar para os índices SPAD e NDVI, que responderam de forma crescente conforme houve aumento da dose de nitrogênio aplicada seguindo padrão similar à produção de massa seca disponível e teor de nitrogênio foliar. A relação entre o teor de clorofila medido com equipamentos portáteis e a concentração de nitrogênio e rendimento produtivo da lavoura tem sido demonstrada em diversas pesquisas (MOREIRA e VIDIGAL, 2011;PARIZ et al, 2011;VIANA et al, 2014 …”