Soybean Root Development Under Low Phosphorus and Water Availabilities.

Soybean is a new crop in Southwest of Buenos Aires province where low soil P availability in some areas of the region and droughts can be serious limitations to soybean production.

The relative immobility of phosphorus in soil makes the disposition of the root system important for P obtention by the plant. Besides, in most cases P available for plants is located in the upper soil layers decreasing with soil depth. Previous results obtained found that P application in a low-P and dry soil relieve soybean water stress symptoms.

A greenhouse experiment was conducted to evaluate the role of the root system of soybean under phosphorus and water deficiencies. Treatments were a factorial combination of three levels of P and three levels of soil water content.

Phosphorus application increased biomass (32%) and plant total P (82%). Soybean root development responded to phosphorus addition. Root architecture was closely related to P absorption. There was an increase of branch roots, mainly in the upper portion of the soil profile with P application.

Phosphorus addition improve the adverse effects of water stress. It was also observed an increase in root dry weight and root lenght allowing the soybean plants to explore more soil volume.