No abstract

S U M M A R YNine rice genotypes were classed as tolerant, moderately tolerant, susceptible and highly susceptible, depending on their growth retardation and the intensity of lime-induced iron chlorosis. All except genotypes IET 7972 and IET 7973 showed varying degreees of chlorosis and corresponding decreases in shoot dry matter production. Chlorosis was negatively correlated with the orthophenanthroline reactive Fe 2+ iron content of the leaves, the concentration of which accounted for 82% of the variability in chlorosis. However, total iron concentration in the leaves and the Fe/Mn, Fe/Cu and K/Fe ratios were not significantly correlated with dry matter accumulation in the plants.Lime-induced iron chlorosis of plants is frequently observed in calcareous soils. Rice grown on medium upland soils displays acute iron deficiency symptoms, the severity of which differs widely amongst different varieties (Ponnamperuma, 1978) so that the selection of suitable genotypes for cultivation in such soils is of great practical importance. The present study investigated the relative tolerance of indica rice genotypes and the causes of their differential susceptibility when grown on calcareous soil. MATERIALS AND METHODSField investigations were carried out at Rajendra Agricultural University, Pusa, Bihar (25° 39' N, 85° 40' E) during the kharif (summer) seasons of 1982 and 1983 on iron deficient, light textured, extremely calcareous soils. Important characteristics of the experimental plots are presented in Table 1. Available iron, zinc, copper and manganese were extracted with DTPA (Lindsay and Norvell, 1978) and estimated with an atomic absorption spectrophotometer. Other soil properties were determined by standard procedures (Jackson, 1967). A randomized block design was used with nine rice genotypes each replicated four times in 15 m 2 plots under upland conditions. The standard evaluation system for screening against iron stress was followed (IRRI, 1976). Observations were recorded three times at eight-day intervals from the 24th day after sowing in all four replicates. Twenty identical 40-day-old plant samples were collected from each genotype, oven dried at 70°C and the dry matter yields of the shoots recorded. The samples were then pulverized in a Waring blender

The agro-eco-sub region (AESR) 4.2 encompasses Aravalli foot hills, central Rajasthan plains and adjoining areas. Visual interpretation of geo-coded satellite data (IRS-P6, LISS IV MX) on the same scale was done before starting the field work. Based on the interpretative units a high intensity detailed soil survey was carried out in cluster of ten villages of Bhadesar tehsil of Chittaurgarh district on cadastral map (1:4000 scale) and the soils were characterized with respect to landforms. In all, 14 soil series were established and assessed for soil site suitability for maize, wheat, mustard and soybean. Daulatpura-c series soils are suitable for maize, mustard, soybean, and Daulatpura-d soils for soybean and moderately suitable for other crops. Soils of Bagund and Narbadiya-a series are moderately suitable for maize and marginally suitable for other crops. The soils of Bhadsoda-b series are marginally suitable only for mustard but moderately suitable for all other crops. Soils of Parliya series are moderately suitable only for mustard crop and marginally suitable for remaining crops. The soils of Guda series are marginally suitable for maize, wheat, mustard but not suitable for soybean. The soils of Nardhari-a and Nardhari-b are moderately suitable, Daulatpura-b, Bhadsoda-a and Narbadiya-b are marginally suitable whereas soils of Madanpura and Daulatpura are not suitable for all the crops due to limitations of shallow soil depth.