Physical and chemical characterisation of the agricultural lands of the Soan-Sakesar Valley, Salt Range, Pakistan

Soil samples (depth, 0-20 cm) from the Soan-Sakesar Valley were analysed fo r a variety of parameters: pH, electrical conductivity (ECe), alkalinity, N a, K, Ca, Mg, Cl, SO4, Li, B, and NO3 in saturation extracts; organic carbo n (C), NaHCO3-extractable phosphorus (P), and total P in whole soil; and mi neralogical investigations in whole-soil and separated clay fractions. A Pr incipal Component Analysis was carried out on the correlation matrix (i.e. on standardised attributes) and soil samples were subdivided into salinity groups. The mean ECe levels of Groups 1-4 were 1.27, 2.75, 2.07, and 5.67 d S/m, respectively; the corresponding sodium adsorption ratios were 5.36, 7. 9, 15.7, and 29.6 mmol(0.5), respectively. In these soil groups, suitable c rops were suggested on the basis of their salt tolerance and the salinity o f the irrigation water. The low availability of P from phosphatic fertilise rs and farmyard manure as a result of fixation by calcite, which is present in these soils to the extent of 7.8-15.2%, resulted in a lower yield of gr ain crops (wheat and maize). On the other hand, higher application rate of nitrogen (N) fertilisers together with farmyard manure to irrigated crops a nd vegetables resulted in N leaching from the crop rooting zone into ground water. The soils investigated had mixed clay mineralogy with a dominance of chlorite, illite, and kaolinite, whereas major non-clay minerals are predo minantly albite, calcite, and quartz.