HUMIC SUBSTANCES AND PHOSPHOROUS SOURCES IN MAIZE CROPS

SUBSTÂNCIAS HUMICAS E FONTES DE FOSFORO NA CULTURA DO MILHO O objetivo do estudo e verificar o efeito da adicao de doses de um produto comercial a base de substâncias humicas (SH), na producao de massa seca de plantas de milho, no acumulo de P nas plantas e a eficiencia agronomica de fontes de fosforo em dois tipos de solos com diferentes capacidades de adsorcao. O trabalho foi conduzido em casa de vegetacao. Os tratamentos compreendem quatro doses de substâncias humicas (0, 100, 200 e 400 kg ha-1) e duas fontes de fosforo (superfosfato triplo – SFT e fosfato natural reativo – FNR), em dois tipos de solos (Latossolo Vermelho – LV e Neossolo Quartzarenico – NQ). As fontes de P foram fornecidas em dose constante de 75 mg.dm-3 de P. Houve resposta estatisticamente significativa (P<0,05) da producao de massa seca da parte aerea (MSPA), massa seca das raizes (MSR), P acumulado na parte aerea e P acumulado nas raizes a adicao de SH. No LV os parâmetros MSPA, MSR, P acumulado na parte aerea, P acumulado nas raizes e a Eficiencia agronomica relativa das fontes de P aumentaram com a adicao crescente de SH, obtendo os melhores resultados com uso da maior dose (400 kg ha-1). No NQ as melhores respostas foram obtidas com a adicao de 100 kg ha-1 da SH. Estes resultados indicam que a utilizacao de substâncias humicas e eficiente para o aumento da producao de massa seca das plantas de milho e no teor de P acumulado.Palavras-chave: P acumulado, eficiencia agronomica relativa, adsorcao de fosforo. ABSTRACT: The objective of this study was to verify the effect of the application of different rates of a commercial product based on humic substances (HS) on the dry matter contents, and P accumulation in maize plants and the agronomic efficiency of phosphorus sources in two soils with different adsorption capacities. The experiment was conducted in a greenhouse. The treatments consisted of four rates of humic substances (0, 100, 200, and 400 kg ha-1) and two phosphorus sources (triple superphosphate – TSP; and reactive natural phosphate – RNP) in two types of soils (Rhodic Hapludox – RH; and Typic Quartzipsamment – TQ). The response of the shoot dry weight (SDW), root dry weight (RDW), shoot accumulated P, and root accumulated P to the application of HS was statistically significant (P <0.05). In the RH, the SDW, RDW, shoot and root accumulated P, and relative agronomic efficiency of the P sources increased with increasing HS rates; thus, the best results were found with the use of the highest rate (400 kg ha-1). In the TQ, the best responses were found with the application of 100 kg ha-1 of HS. These results indicate that the use of humic substances is efficient to increase dry matter and accumulated P contents in maize plants.Keywords: accumulated P, relative agronomic efficiency, P adsorption.