Influence of phosphorus and biofertilizers on soybean and wheat root growth and properties

• Inoculation of PSB and VAM with 50% P enhanced P inflow rate with comparison to 100% P application, although highest rhizosphere P was recorded in later.
• Acquisition of P is more important than higher soil available P for root growth and grain yield
• PSB and VAM with 50% P dramatically enhanced root CEC, root length density and other root properties with comparison to 100% P application.
• Root CEC and root length density significantly influenced other root properties and grain yield of soybean and wheat.
• Inoculation of PSB and VAM substituted 50% P application for grain yield in soybean–wheat cropping system.

Alteration of crop root morphology is a new innovative approach to provide food security. Phosphorus is the most important nutrient to influence root properties. Efficient use of P fertilizers has become an important issue of agriculture all over the world due to limited availability of rock phosphate and its non-renewable nature. Hence, root properties and grain yield of soybean–wheat cropping system were evaluated by inoculation of phosphate solubilizing bacteria (PSB) and vesicular arbuscular microorganism (VAM) with 50% recommended P (0.5 P + PSB + VAM) against 100% P (1.0 P), 50% P and control in a Typic Ustochrepts of the Indo-Gangetic plains. The root cation exchange capacity (CEC) of soybean and wheat treated with 0.5 P + PSB + VAM were 3.6 and 4.6% higher than 1.0 P, respectively. The same treatment produced 2.3 and 2.6% higher root length density (RLD) in soybean and wheat, respectively in comparison to 1.0 P. The P inflow rate under 0.5 P + PSB + VAM was 9.2 and 4.6% higher than 1.0 P in soybean and wheat, respectively indicating higher acquisition of P through VAM, although higher rhizospheric P availability was recorded in 1.0 P. The root CEC, RLD and P inflow rate were closely related to P concentration and content in root, shoot and nodule, specific root length, root diameter and internal P requirement. The better root property observed in 0.5 P + PSB + VAM enhanced 4.1 and 4.9% grain yield of soybean and wheat, respectively as compared to 1.0 P. Inoculation of PSB and VAM could substitute 50% P of soybean–wheat cropping system with better root property and higher grain yield in semi-arid sub tropics of the Indo-Gangetic plains.