Nutrição e crescimento do tomateiro em função da interação de substâncias húmicas com B, fontes de Ca e formas de N mineral

Abstract

Humic substances (HSs) interact with boron (B), complex calcium (Ca) and regulate the absorption and efficiency of use of mineral N forms, as a result, they can ensure greater nutrient uptake, dry matter (DM) production, root growth, and increased crop yield. This study was carried out to evaluate the effects of the interaction of increasing concentrations of humic acid (HA) with the availability of B in soil, Ca sources and the concomitant use of HA and fulvic acid (FA) concentrations with forms and proportions of mineral N on the tomato nutrition and growth. In the first chapter, it was adopted a double factorial of 2 (availability of B in soil) x 5 (C-HA concentrations), using three replications. Rhodic and clayey Oxisol samples used incubated with concentrations of 0, 5, 10, 50 and 100 mg kg-1 of C-AH, in combination with two concentrations of B in soil: without addition or B application of increase the content in soil to 2 mg kg-1. We analyzed the DM of aerial part (AP), root (R) and total (AP+R) and the DM ratio of R/AP and the B accumulation in the AP. The availability of B in soil modulates the DM and regulates the effect of C-HA concentrations on tomato, mainly when B is in high availability in soil. In the second chapter, it was adopted a factorial of 2 (Ca sources) x 5 (C-HA concentrations), in three replications. The experiment was conducted in greenhouse conditions, using samples a Rhodic samples with a medium texture, sampled at 0-10 and 20-40 cm soil depth, and the treatments consisted of the combination of CaCO3 and CaSO4 with concentrations of 0, 5, 10, 50 and 100 mg kg-1 of C-HA. After soil samples incubation with the treatments, tomato seedlings were transplanted analyzed in regard to AP, R and total DM (AP+R). The effect of C-HA concentrations is more pronounced in the root DM than in the AP and there are higher total DM when CaCO3 is applied in soil in comparison to CaSO4. In the third chapter, it was adopted a factorial 3 N-NO3-: N-NH4+ ratios: 70:30, 50:50 and 30:70, respectively, x 5 C-HA and C-FA concentrations, in three replications. Washed sand samples were incubated with the concentrations of 0, 5, 10, 50 and 100 mg kg-1 of C-HA and C-FA, with nutrient supplying via nutrition solution. After the sand was incubated with these treatments, tomato seedlings were transplanted and, after 35 days of cultivation, DM was analyzed for AP, R and total (AP+R) and the chemical composition of the growth medium was analyzed. The sand solution was sampled at the beginning of the crop transplanting. The effect of concentrations of C-HA and C-FA and proportions of N-NO3-, NH4+ and N differ from each other. Prevalence of N-NO3- over N-NH4+ implied in higher tomato DM than concentrations of HSs and other mineral N form proportions.