Importance of arbuscular mycorrhizal technology relying on exploitation of native flora for improving P nutrition of upland rice has been established and technology module has been developed. One of the components of such technology module is application of on-farm produced AM fungal inoculum of native origin for which production protocol and optimum dose for upland rice has been worked out. However, under precision farming system, inoculum needs to be applied based on site and system specific precise dose requirements to avoid excess or less (than requirement) application. To address this issue, efforts were made to develop mathematical model for determining AM (arbuscular mycorhiza) inoculum requirement under known soil phosphorus (available) and AMF population level for targeted P uptake by rice crop. Two such models for AM-responsive and non-AM-responsive varieties were developed.

(1) For moderately AM-responsive variety (eg, Vandana)
P uptake= -1.734 +(0.013 x Soil P conc) + 0.004 x AM spore population
R2= 75.81; cv= 18.17
(2) For AM-non-responsive variety (eg, Jonga)
P uptake= 1.41+(0.01 x Soil P conc) - 0.00001 x AM spore population
R2=59.61; cv= 27.80
Where;
Growth rate= dry matter production /day / plant in g
Soil P conc.= P in ppm
AM spore population= AM spore number / 100 g soil