Effects of long-term organic and chemical fertilization on N and P in wheat plants and in soil during crop growth

A 34-year long-term fertilizer experimental (LTFE) site on a Typic Haplustept at the Indian Agricultural Research Institute (New Delhi) was used for the present study. The objective was to investigate the effect of six fertilizer and farmyard manure (FYM) treatments (Control, N, NP, NPK, NPK + S, NPK + FYM) and three physiological stages (tillering, flowering and dough) of wheat crop on the pattern of mineral N (NH4+ and NO3-), mineralizable N and Olsen-P dynamics in soil, and concentration of N and P in wheat crop during November 2004 to April 2005. A balanced application of NPK (i.e. 100% NPK) + fannyard manure (FYM) showed highest values of the above observations and control (0 NPK) showed the lowest. Growth stages of wheat crop affected the Studied parameters significantly (p < 0.05), being highest at tillering followed by flowering and dough stages. A significant positive interactive effect of fertiliser treatments and stages of wheat growth was also recorded for N and P availability in soil and their uptake by wheat crop. Stepwise regressions have revealed that grain yield of wheat was significantly associated with mineralizable N at tillering (R-2 = 0.80), NO3-N at flowering (R-2 = 0.73), and Olsen-P and Plant-P (R-2 = 0.87) at dough stage of wheat growth. The results indicate that in the background of long-term fertility management regimes, crop growth (rhizospheric feed back) stages have significant impact oil the nutrient dynamics in soil and nutrient concentration in growing plants.