Field study was conducted on slightly alkaline alluvial soil at Modipuram (U.P.) to ascertain the effect of PK fertilizers and farmyard manure (FYM) on the potato-wheat crop rotation during 1979–80 and 1980–81. Application of 20 and 40 kg P/ha increased the potato yield and P uptake by tubers but the differences were non significant in both years but significant in pooled data. Application of 40 and 80 kg K/ha increased the potato yield and PK uptake by the tubers significantly. The highest tuber yield and PK uptake by the tubers was obtained by the interaction of 20 kg P and 80 kg K/ha. The application of 30 tonoes FYM/ha was at par with 20 kg P plus 80kg K/ha, with respect to tuber yield and uptake of PK by the tubers. The effect of PK fertilizers and FYM was significant on the yield of large size tubers only. The residual effect of PK fertilizer and FYM was quite pronounced on the succeeding wheat crop. The economic optimum doses of P,K fertilizers and FYM for potato were 15.7 kg P, 112 kg K and 26.2 tonnes FYM/ha.
