Published online by Cambridge University Press: 27 March 2009
A field experiment was conducted on acid soil of Kufri (Shimla) from 1980 to 1982 to study the effect of 30 t farmyard manure/ha (FYM) and 88 kg P + 160 kg K/ha (PK) on the response of potatoes to N fertilizer and on soil properties. There was a highly significant response of potato to N and the response was greater in the presence of PK than in the presence of FYM. The dose of N for maximum tuber yield with PK (39·9 t/ha) was 194 kg/ha, whereas for maximum yield with FYM (33·2 t/ha) it was 128 kg/ha. FYM met the P and K needs of potato when 100 kg N/ha was applied but not when 180 kg N/ha was applied. N fertilizer increased N concentration but decreased P and K concentration in leaves and tubers. The concentration of P and K was higher but that of N was lower with PK than with FYM. N fertilizer enhanced the uptake of P and K but its effect was not significant with FYM.
After 3 years of treatment FYM improved organic carbon, total N and NO3 status of the soil. N as calcium ammonium nitrate increased organic carbon in the presence of PK but decreased it in the presence of FYM. N fertilizer had little effect on total N, NO3 and available P content. N application depleted available K and the depletion was proportionate to the rate of N applied. The application of FYM and PK increased available P and K content of the soil and the increase was more with PK than with FYM.