Influence of 35 years continuous inorganic fertilization on soil properties and wheat yield

This investigation comprised of both laboratory as well as field studies on soils collected after 35 years from long-term maize-wheat fertilizer experiment, initiated at Punjab Agricultural University Farm, Ludhiana in 1971 and is still in progress. The soil tested sandy loam, alkaline in nature (pH, 8.8), normal in soluble salt concentration (EC, 0.20 dSm⁻¹), low in OC (0.20%) and available-N (81 kg ha⁻¹) and medium in Olsen-P (14 kg ha⁻¹). Continuous addition of fertilizers resulted in decreased soil pH, and maximum decrease in soil pH was observed in N₂₀₀ P₄₄K₈₂ (from 8.8 to 7.7) treatment. There was no effect on EC with the continuous addition of inorganic fertilizer, however, the addition of super-optimal dose of inorganic fertilizers (N₂₀₀P₄₄K₈₂, N₂₀₀P₄₄K₈₂Zn₁₀,) resulted a slight increase in EC. The OC of all the fertilizer treated plots increased with the continuous addition of fertilizers. Available nutrient status (N and P) also improved with the continuous addition of inorganic fertilizers. In the field experiment, N content in wheat plant increased with increasing level of N. The dry matter yield and P uptake increased with P application. The maximum P content was obtained in N₂₀₀P₄₄K₈₂Zn₁₀ treatment (0.49 and 0.14 per cent in grain and straw) whereas the minimum P content (0.10 and 0.06 per cent in grain and straw) was observed in check plot. As the residual P status of soil increased, dry matter production also increased correspondingly and the effect was statistically significant.