Effect of Phosphorus Supply on Soybean Plant Response to Water Deficit.

Preliminary results found that increased phosphorus application to soybean plants in a low-P and dry soil, relief their water deficit symptoms. To get a better understanding of this response experiments were conducted at Nueva Roma (38°30'S 62°39'W) in the semiarid region of Argentina and in the greenhouse. Treatments were a factorial combination of three levels of P supply and three levels of soil water availability. Measurements were made of the plant and leaf growth, root system and water status of the soybean plants.

Under water deficiency only plants grown with a high level of P concentration kept a fairly high conductance and water potential and improve water use efficiency. An increase in soil P availability could partially surpass water deficit effects on leaf appearance rate, leaf area, aboveground biomass and dry weight of roots, and also increased plant recovery upon rewatering.

Higher P rates were able to partially overcome effects of a dry soil, as a result of larger P and water uptake.