Correlation of Different Soil Tests With Maize Response for Nitrogen and Phosphorus at Different Fertility Levels of the Soil

Relationships between soil tests for available nitrogen and phosphorus with grain yield and nutrient uptake in maize crop (Zea mays) were worked out in soils of different fertility gradients, created artificially, on one piece of land. Fertility gradient was not found to be established with respect to organic carbon and available nitrogen; slight increase in available phosphorus level was observed blockwise.

Organic carbon per cent gave higher correlation values with nitrogen uptake and yield as compared with alkaline permanganate method showing thereby, that per cent organic carbon is a better index as an estimate of available nitrogen for first depth of soil samples (0–15 cm). Likewise, Olsen's method was found to be better index of phosphorus availability. In second depth of soil samples (15-30cm) contents of organic carbon and available phosphorus (Olsen's method) were found to be correlated with yield and nitrogen uptake and phosphorus uptake respectively.