Phosphorus fertilization improves soybean growth under salt stress

Abstract

Soybean is one the most important crop in the world. This crop has expanded its cultivated area for
regions with saline soils in several parts of the world. This fact occurs because of the large increase of
the soybean productivity in recent decades, in parallel with an increasing demand for food. This work
aimed to evaluate the salinity effects on the plant growth, and the interaction of phosphorus fertilization
versus irrigation water salinity in soybean plants. The experiment was conducted in a greenhouse
using recipients contained 6.0 dm3 of mixture sand and commercial substrate (1:1 v/v). Five salinity
levels in the irrigation water (0.8, 2.2, 3.6, 5.0 and 6.4 dS m-1) and two levels of phosphorus fertilization
(0 and 300 mg L-1) were evaluated. After 36 days, the salt stress promoted reductions in the most of the
growth variables, such as stem diameter, plant height, number and average length of branches, root
length, shoot and root dry mass, and absolute growth rate. On the other hand, it increased the
chlorophyll relative index, chlorophyll a and total content, and shoot/root dry mass ratio. The
phosphorus-supplemented plants had higher stem diameter, number of branches, shoot dry mass and
absolute growth rate. The salt stress-phosphorus interaction showed that the phosphorus attenuated
the salt stress deleterious effects only on leaf area after 5 dS m-1 of saline water. Soybean plants can be
irrigated using water with electrical conductivity up to 1.9 dS m-1 without disturbing its biomass
components. The phosphorus fertilization improves the growth soybean subjected to salt stress but not
reduce the salinity deleterious effects.