Influence of cadmium on dry matter yield, micronutrient content and its uptake in some crops.

The study was conducted to evaluate the accumulation pattern of cadmium (Cd) and its tolerance in different crops grown on sewage irrigated soils with differentCd levels. Growth, yield, uptake and tolerance of maize, raya, berseem and spinach were assessed to different levels of Cd ranging from 0-40 mg kg(-1) soil. Significant reduction in dry matter yield in raya was observed at 20 mg Cd kg(-1) soil where as for other crops it was 10 mg Cd kg(-1) soil. The quadratic models seem to give the best description of variation in dry matter yield with Cd levels as revealed by significant coefficient of determination (R2 > or = 90). Cadmium content and uptake varied in the following order: raya > spinach > maize > berseem. Raya could tolerate high levels of Cd as compared to other crops. Conversely, berseem and maize which showed reduced ability to absorb or translocate Cd for genetic reasons compared to raya and spinach be preferred for growing on sewage irrigated soils or area having increased Cd-levels. The relationship of Cd with other micronutrients was variable.

Effect of farm yard manure on chemical fractionation of cadmium and its bio-availability to maize crop grown on sewage irrigated coarse textured soil.

Cadmium is a potentially toxic heavy metal that enters food chain from the soil through various anthropogenic sources. Availability of metal ions in contaminated soils can be reduced by the addition of organic amendments. In this study, effect of organic matter -farm yard manure (FYM) amendment on fractionation and availability of Cd to maize was evaluated. A green house experiment was conducted to determine the toxicity and uptake of Cd by maize in sandy loam soil with and without organic matter. Four levels of Cd (0, 10, 20 and 40 mg kg(-1) soil) and two levels of FYM (0 and 20 tonnes ha(-1)) with three replication in a completely randomized factorial design. Concentration of Cd in maize increased with increasing rate of Cd application. Application of organic matter increased the dry matter yield of maize while reduced the uptake of metal. All the fractions exhibited increase with Cd rates. The addition of organic amendment declined significantly the concentration of water soluble and exchangeable Cd, but increased the amounts of these metals into less mobile fractions (Fe/Mn oxide, organic matter and residual). Dominance of insoluble forms of Cd after the application of organic amendments may be ascribed to the increases of soil OM, pH, EC and available P contents which caused transformation or redistribution of the sorbed phases. This resulted in increasing Cd retention in the more persistent fractions with application of FYM at the expense of reductions in the loosely bound fractions. Thus FYM appears to be agronomically feasible way to off set the adverse effect of Cd toxicity.

Suitability of village pond waters for irrigation-a case study from district Ludhiana, India.

The village ponds were used for storing rainwater for animals and recharging of underground water. Recent developments like public water supply for household purpose, provision of household wastewater concrete channels, and toilet septic tanks have polluted the village ponds. The infiltration of water has decreased due to non-cleaning of silt from the pond beds. Increased discharge of wastewater from households, coupled with a low infiltration rate, has inundated these ponds. People have abandoned the use of this water for animals. An effort has been made to assess the suitability of this water for irrigation in the vicinity so as to clean these ponds. Seventy-eight water samples were collected from the village ponds in the Ludhiana district of Punjab. The samples were analyzed for total solids (TS), total dissolved solids (TDS), total suspended solids (TSS), biological oxygen demand (BOD), chemical oxygen demand (COD), electrical conductivity (EC), residual sodium carbonate (RSC), nitrogen, water soluble P and K, as well as micronutrients and pollutant elements. The total solids content of these waters were on the higher side. Considering TSS, BOD, and COD, some of these waters are unsafe for their disposal in river or water bodies. Electrical conductivity ranged from 693 to 5050 µmhos/cm, and RSC varied between -1.9 and 22.8 meq/l. The inorganic N (NH+4+ NO-3-N) and total Kjeldahl N ranged from 3 to 30 and 8 to 41 mg/l, respectively. The amount of micronutrients (Zn, Cu, Fe, and Mn) present in pond water indicated its high nutrient value. The content of the pollutant elements such as nickel, cadmium, and lead was below the maximum permissible limits, thereby indicating its suitability for irrigation. According to the EC and RSC criteria, 18% of the samples were fit, 31% were marginal, and 51% were unfit for irrigation. The data indicate that these waters are a good source of nutrients for agriculture.

Impact of sewage irrigation on speciation of nickel in soils and its accumulation in crops of industrial towns of Punjab.

Analysis of soil samples collected from sewage and tube well irrigated soils of Ludhiana, Amritsar Jalandhar and Mandi Gobindgarh, revealed that Diethylene triamine pentaacetic acid extractable nickel ( DTPA-Ni) was found to be higher in sewage fed soils. Sewage irrigation increased soil DTPA-Ni content by 3.04 times over the tube well irrigated soils. The content of DTPA-Ni showed decreasing trend with depth. Hydrogen concentration (pH) was negatively and significantly correlated with DTPA-Ni nickel whereas, organic carbon and total Ni show positive and significant correlation. Sequential fractionation was carried out to partition Ni in to fractions namely exchangeable and water soluble, organic bound, carbonate bound, Mn oxides bound, amorphous Fe oxides, crystalline Fe oxides bound and residual. Plant availability of these fractions is believed to decrease in the above order. Sequential fractionation indicated that every extracted fraction exhibited increase in Ni content with sewage irrigation with most prominent increases occurring in the organic and oxide fractions. The lowest amount of Ni in exchangeable and water soluble and the highest in residual pools testify that plants grown on these soils may not suffer from Ni toxicity. Though all the crops irrigated with sewage water had appreciably higher concentration of Ni as compared to the crops raised with tube-well water yet raya (Brassica juncea) and toria (Brassica campestris) accumulated higher content of heavy metals as compared to other crops, with higher content in roots than shoots. Transport index suggested that major part of taken up Ni is translocated to top parts of plant. Based on values of transport indices, different crops maybe arranged as toria > raya = maize > bajra > lady finger. As the plants take up nickel readily and there is danger of its excessive accumulation in plant organs and devaluation of the plant products. This is topical issue particularly in crops used for direct consumption.