Department of Soils, Punjab Agricultural University, Ludhiana, Punjab, 141004.
1Present address: Department of Civil Engineering, Punjab Agricultural University, Ludhiana, Punjab, 141004.
The results on the influence of differential levels of urea and manures addition to rice or wheat alone or to both the crops in a rice-wheat sequence on the distribution of mineral N content in the soil profile at various stages of rice growth are reported. Mineral N content (NH4-N and NO3-N) at various soil depths in residual manuring phase (M3) was considerably lower than in plots representing cumulative (M1) and direct manuring (M2) phases. Peak NO3-N concentrations were observed at 60–90, 90–120 and 120–150 cm soil depths at 35 and 70 DAT and at rice harvest, respectively. However, peak NH4-N concentration at these three sampling stages occurred at 15–30, 30–45 and 45–60 cm soil depths. Substitution of 60 kg N through biogas slurry (BGS) or farmyard manure (FYM) at both levels of applied N reduced movement of mineral N to lower depths. The concentration of NO3-N in the soil profile decreased with increasing stage of crop growth in each of the manuring phase, irrespective of the fertilizer treatment. At rice harvest, NO3-N content in M1, M2 and M3 manuring phases was nearly 40.4 to 43.3, 40.3 to 44.2 and 40.1 to 43.8 per cent, respectively, of that recorded at 35 DAT. The concentration of NH4-N in the soil profile followed the same trend as exhibited by NO3-N. Among the two organic sources used for N substitution, NO3-N as well as NH4-N accumulation in the soil was higher with biogas slurry application iu each of the manuring phase.
Mineral N, soil profile, stage of rice
