Alleviation of temperature stress in maize by integration of foliar applied growth promoting substances and sowing dates.

Temperature is a key factor influencing plant growth and productivity, but its sudden rise can cause severe consequences on crop performances. Early sowing and application of growth promoting agents as a foliar spray can be a sustainable approach to cope with high temperature stress at grain filling stage of cereal crops. Therefore, a test was designed to explore the potential of different growth helping agents including sorghum water extract (SWE, 10 ml L-1), moringa leaf extract (MLE, 3%), hydrogen peroxide (H2O2, 2 µM), salicylic acid (SA, 50 mg L-1) and ascorbic acid (ASA, 50 mg L-1) as foliar agents at different sowing dates (early and optimum) to cope with temperature stress in maize. The results stated that foliar application of growth promoting substances successfully persuaded high temperature tolerance at reproductive phase of maize in early and optimum sowings when compared to control. However, SWE + ASA, MLE + H2O2 and SWE + ASA + SA + H2O2 were the best combinations for improving growth, development, and physiological variables under both sowing dates even under suboptimal temperature. All foliar applications significantly increased maize grain and biological yields while maximum was observed in SWE + ASA followed by SWE + ASA + SA + H2O2 or MLE + H2O2 that were statistically at par with ASA + SA + H2O2 but plants without spray or distilled water application did not improve grain and biological yields. Overall, the foliar applications of growth promoting substances enable the plant to enhance its growth, development, morphology, yield and biochemical variables.

Effects of co-addition of ammonium, nitrite, and glucose with methionine on soil nitrogen.

Methionine is one of the many amino acids in the soil. In order to study the role of methionine in acidic forest soil, the effect of methionine (Met) was compared with control together with addition of ammonium (Met + A), nitrite (Met + N), and glucose (Met + C) under 60% or 90% water holding capacity (WHC), because ammonium and nitrite are important factors in nitrification, and glucose affect the heterotrophic nitrification and nitrogen immobilization. We found that methionine addition significantly reduced NO3- concentration in acidic forest soil. Compared to Met, Met + A and Met + N treatments non-significantly enhanced nitrification; however, Met + C treatment decreased NH4+ concentration which suggested that soil autotrophic and heterotrophic nitrification were limited in the presence of methionine at 60% WHC. Further, our findings of 15N-labeled treatment showed the impact and priming effect of methionine was negative for NO3- concentration and positive for N2O emission, which were observed mainly from the soil N source rather than methionine. At 90% WHC, Met + C treatment significantly lessened concentrations of NH4+ and NO3-, nonetheless improved N2O compared to Met treatment. Therefore, besides the denitrification and dissimilatory NO3- reduction to ammonia, the immobilization might be the key factor to explain this decrease in NO3- concentration at 90% WHC, while these processes were induced with the C addition. This study indicated that the positive role of amino acids in soil N cycling might be overrated.