Effect of farmyard manure on distribution of photosynthates and efficiency of nitrogen utilization by potato

Pot experiments were conducted on sandy clay loam acid soil of Simla during three seasons (winters 1977 & 1978 and summer 1978) to evaluate tbe role of FYM in N nutrition of potatoes. Farmyard manure (FYM), calcium ammonium nitrate (CAN) and FYM+CAN (1:1 on N basis) were compared @ 50, 100, 150 and 200 mg N/kg soil. FYM was less effective than CAN. The combined application of FYM and CAN, however, gave 2.67 time higher tuber yield than CAN alone due to higher percentage of photosynthates translocated from tops to tubers and improvement in N utilization by potatoes. CAN gave larger yield of tops and higher N concentration in plant than the combined application of FYM+CAN which led to reduced translocation of photosynthates and decreased efficiency of N utilization. The effects of FYM on the translocation and N utilization efficiency were more striking in summer crop (grown under high temperatures and long day conditions) than in winter crops (grown under normal temperatures and short day conditions). Apparent recovery of N was 56% from CAN, 47% from CAN+FYM and 20% from FYM. N balance indicated gains in soil N in FYM treatments while deficits in CAN treatments.

Soil analyses made after three dressings of manurial treatments showed an increase in N by N application. FYM showed highest increase in organic carbon, total-N and K₂Cr₂O₇ oxidisable N while CAN showed highest increase in alkaline KMnO₄ oxidisable-N, NH₄-N and NO₃-N. C/N ratio of soil was increased by FYM.