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ABSTRACTThe use of eggshells as an alternative source of calcium carbonate for groundnut can reduce the impact on the natural reserves of limestone, a non-renewable natural source. This study aimed to investigate the effects of eggshell powder application on the growth and yield of groundnut. The calcium treatments were lime application (A0) at 500 kg ha−1and four rates of eggshell powder application including A1 (200 kg ha−1), A2 (300 kg ha−1), A3 (400 kg ha−1), and A4 (500 kg ha−1). Two application times, T1 (applying 5-days before sowing) and T2 (applying 5-days after flowering) were employed. The result showed that eggshell powder could be a useful alternative source to supply Ca for groundnut. Application of eggshell powder before sowing resulted in significantly higher pod yield and total calcium uptake with better growth parameters than after flowering. Increasing eggshell powder application rates also increased soil pH and calcium contents, and plant calcium uptake. The application rate of eggshell powder before sowing at the rate of 300 kg ha−1produced the highest pod yield and was suggested to be optimum.

AbstractDrought stress which often occurs during early growth stage is one constraint in sugarcane production. In this study, the response of sugarcane to drought and nitrogen application for physiological and agronomical characteristics was investigated. Two water regimes (well-watered and drought stress from 60 to 120 day after transplanting) and four nitrogen levels (0, 4.4, 8.8 and 13.2 g pot−1equivalent to 0, 90, 180 and 270 kg ha−1, respectively) were assigned in a Split-plot design with three replications. The results showed that photosynthetic responses to light intensity and intercellular CO2concentrations of sugarcane were different between fertilized and non-fertilized treatments. Photosynthetic rates of 180 and 270 N treatments, normally, were significantly higher than that of 90 N, but not significant at drought conditions. Photosynthetic rates of 0 N treatment were the lowest under both conditions. Higher nitrogen application supported higher photosynthetic rate, stomatal conductance, and chlorophyll content because of higher nitrogen concentration accumulated into the leaf. Drought significantly reduced the potential photosynthetic rate, stomatal conductance, SPAD, leaf area, and biomass production. Higher nitrogen applications with larger root system could support higher photosynthetic activities to accumulate more dry mass. Strong positive coefficient between photosynthetic and biomass nitrogen use efficiency and drought tolerance index may suggest that higher nitrogen use efficiency could help plants have higher ability to tolerate drought stress.