Soil samples were collected from 13 locations in Haryana, after irrigation with sewage water for the past 10–15 years, and were analysed for heavy metals (Cd, Cu, Zn and Ni) and physicochemical properties, such as pH, EC, C, N, and total and available (DTPA-extractable) P. The total heavy metal contents in the soils ranged from 1.3–6.7 mg kg
for Cd, 55.8–353.2 mg kg
for Cu, 356–1028 mg kg
for Zn and 90.0–199.7 mg kg
for Ni. Though soil sample size was small, a significant negative correlation was observed between the organic C and Ni contents in the soil (r
= −0.870, P=0.01). The survival of
(strain PRH 1) and
(B 48) tagged with green fluorescent protein (
) was monitored in liquid culture as well as in the above soil samples. In liquid culture the order of heavy metal toxicity for both strains was Cd>Ni>Cu≥Zn. Soils receiving sewage water showed a 25–97% reduction in the viable cell number of
strains. Available Cd showed a positive correlation and the other three metals a negative correlation with the reduction in cell numbers in both the strains.
The functional diversity of native mesorhizobial genotypes nodulating chickpea was assessed using two chickpea cultivars under pot culture conditions. The symbiotic effectiveness ratio of the mesorhizobial genotypes showed the existence of wide functional diversity among the isolates in Haryana soils. Mesorhizobial isolates belonging to the third genotype (MG III) were more efficient than the other genotypes. The majority of the isolates (94%) had intermediate effectiveness and only a very small percentage (2%) were ineffective, while 4–6% of the isolates were highly effective with a symbiotic ratio > 4.0. These included CP2381A, CP741, CP1423 and CP2437. Among all the isolates, strain CP2381A was the most efficient isolate for both cvs HC1 and HC5. The symbiotic ratio of the shoot N contents varied for both the cultivars after inoculation with mesorhizobial isolates from different districts. The most efficient chickpea mesorhizobial isolates were found to be present in soils from the Bhiwani district followed by that from RDS Farm, Hisar, but isolates from Mahendragarh, Fatehabad and Jhajjar were less efficient.
This work investigated the effect of graded doses and methods of application of digested spent wash on seed germination, nodulation, photosynthetic activity and nutrient uptake in chickpea and on soil properties. Under laboratory conditions, lower concentrations of digested spent wash were not inhibitory to seed germination, whereas higher concentrations led to poor seedling growth and delayed seed germination. However, under greenhouse conditions, seed germination was slightly better at higher concentrations. Increased concentrations of digested spent wash affected the nodulation of chickpea. Irrigation with digested spent wash in pots had an adverse effect on nodulation as compared to its soil application. Lower concentrations of digested spent wash had no detrimental effect on plant growth (shoot length, root length and their weight). The photosynthetic activity of chickpea plants, measured as chlorophyll a fluorescence, was maximum at 10% and 100 m3 ha−1 of digested spent wash, while a decrease was observed at higher concentrations. With an increase in the concentration of digested spent wash, there was a decrease in N and P uptake by chickpea plants. No significant difference was observed in soil pH, but the EC, organic carbon and total N and P contents of post-harvest soil increased with an increase in the concentration of digested spent wash.