Interference from the vertical variation of soil phosphorus and from water stress on growth in maize, the soybean and sunflower

Resumo

The distribution of phosphorus (P) in the soil interferes with the availability of the nutrient and can affect plant
growth. The aim of this study was to compare the growth and accumulation of P in maize, soybean and sunflower plants in
vertical gradients of the nutrient in the soil, with and without water stress. The design was completely randomised with five
replications, in a 3 x 2 factorial scheme: three soil depth gradients of P (decreasing, increasing and nil) and two conditions of
soil water availability (with and with no water stress). The depth gradients of P were in decreasing doses of P2O5
(300, 200,
100 and 0 mg dm-3), increasing doses (0, 100, 200 and 300 mg dm-3) and equal doses (150 mg dm-3) applied to the intermediate
layers between 0.0-5.0, 5.1-10.0, 10.1-15.0 and 15.1-20.0 cm. Height, dry weight and P accumulation in the roots and shoots
were quantified. The data were submitted to analysis of variance, and mean values compared by Tukey’s test (p<0.05). The
distribution of P in the soil did not interfere with growth or nutrient accumulation in the soybean. Phosphate fertiliser located
in the surface or subsurface layers favoured greater growth and the accumulation of P in the maize and sunflower, compared to
the uniform distribution of the nutrient in the 0-20 cm layer. The increase in phosphate fertiliser at depth did not increase growth
or P accumulation in the three crops, even under conditions of water stress.