Toxicity of Cadmium and nickel in the context of applied activated carbon biochar for improvement in soil fertility.

Toxicity induced by heavy metals deteriorates soil fertility status. It also adversely affects the growth and yield of crops. These heavy metals become part of the food chain when crops are cultivated in areas where heavy metals are beyond threshold limits. Cadmium (Cd) and nickel (Ni) are considered the most notorious ones among different heavy metals. The high water solubility of Cd made it a potential toxin for plants and their consumers. Accumulation of Ni in plants, leaves, and fruits also deteriorates their quality and causes cancer in humans when such a Ni-contaminated diet is used regularly. Both Cd and Ni also compete with essential nutrients of plants, making the fertility status of soil poor. To overcome this problem, the use of activated carbon biochar can play a milestone role. In the recent past application of activated carbon biochar is gaining more and more attention. Biochar sorb the Cd and Ni and releases essential micronutrients that are part of its structure. Many micropores and high cation exchange capacity make it the most acceptable organic amendment to improve soil fertility and immobilize Cd and Ni. In addition to improving water and nutrients, soil better microbial proliferation enhances the soil rhizosphere ecosystem and nutrient cycling. This review has covered Cd and Ni harmful effects on crop yield and their immobilization by activated carbon biochar. The focus was made to elaborate on the positive effects of biochar on crop yield and soil health.

Improvement in growth and yield attributes of cluster bean through optimization of sowing time and plant spacing under climate change scenario.

Cluster bean (Cyamopsis tetragonoloba L.) yield has plateaued due to reduction in rainfall and rise in temperature. Therefore, its production cycle could not get appropriate water and temperature. It becomes important to standardize the sowing time and plant spacing of cluster beans in changing climate scenarios to get higher productivity. Therefore, a field study was conducted in 2019 at the Research area of MNS-University of Agriculture, Multan, Pakistan to evaluate the effect of four sowing times (15th May, 1st June, 15th June, and 1st July) and three plant spacings (10, 12 and 15 cm) on crop growth, yield, and physiological functions of cluster bean genotype BR-2017 under split plot arrangement under randomized complete block design (RCBD) with three replications. The sowing times (15th May, 1st June, 15th June, and 1st July) were placed in the main plot, while plant spacing (10, 12 and 15 cm) was maintained in subplots. The significant effect of sowing time and plant spacing was observed on pod plant-1, pod length, grain yield, and 1000-grain weight. Results showed that 1st June sowing performed better over 15th May, 15th June, and 1st July, while plant spacing 15 cm about in all sowing times showed higher results on growth and yield parameters of cluster bean over plant spacing 10, 12, and 15 cm. The 1st June sowing time at 15 cm plant spacing showed 8.0, 22.7, and 28.5% higher grains pod-1 than 15th May, 15th June, and 1st July sowing, respectively. Maximum grain yield was observed on 1st June in all three spacings (10, 12, and 15 cm). The chord diagram indicates that the crop has received optimum environmental conditions when sown 1st June over other sowing times. In conclusion, 1st June sowing with 15 cm plant spacing could be a good option to achieve maximum productivity of cluster bean under changing climate scenario.

Mitigation of lead (Pb) toxicity in rice cultivated with either ground water or wastewater by application of acidified carbon.

Toxicity induced by a high concentration of lead (Pb) can significantly decrease plant's growth, gas exchange, and yield attributes. It can also causes cancer in humans. The use of organic amendments, especially biochar, can alleviate Pb toxicity in different crops. The application of biochar can decrease the uptake of Pb by plant roots. However, the high pH of thermo-pyrolyzed biochar makes it an unfit amendment for high pH soils. As Pb is an acute toxin and its uptake in rice is a major issue, the current experiment was conducted to explore the efficacy of chemically produced acidified carbon (AC) to mitigate Pb toxicity in rice. Lead was introduced in concentrations of 0, 15, and 30 mg kg-1 soil in combination with 0, 0.5, and 1% AC, underground water (GW) and wastewater (WW) in rice plants. The addition of 1% AC significantly improved the plant height (52 and 7%), spike length (66 and 50%), 1000 grains weight (144 and 71%) compared to 0% AC under GW and WW irrigation, respectively at 30 mg Pb kg-1 soil (30 Pb) toxicity. Similar improvements in the photosynthetic rate, transpiration rate and stomatal conductance also validated the effectiveness of 1% AC over 0% AC. A significant decrease in electrolyte leakage and plant Pb concentration by application of 0.5 and 1% AC validates the effectiveness of these treatments for mitigating 30 Pb toxicity in rice compared to 0% AC under GW or WW irrigation. In conclusion, 1% AC is an effective amendment in alleviating Pb toxicity in rice irrigated with GW or WW at 30 Pb.

Effect of carbon-enriched digestate on the microbial soil activity.

OBJECTIVES: As a liquid organic fertilizer used in agriculture, digestate is rich in many nutrients (i.e. nitrogen, phosphorus, sulfur, calcium, potassium); their utilization may be however less efficient in soils poor in organic carbon (due to low carbon:nitrogen ratio). In order to solve the disadvantages, digestate enrichment with carbon-rich amendments biochar or humic acids (Humac) was tested. METHODS: Soil variants amended with enriched digestate: digestate + biochar, digestate + Humac, and digestate + combined biochar and humic acids-were compared to control with untreated digestate in their effect on total soil carbon and nitrogen, microbial biomass carbon, soil respiration and soil enzymatic activities in a pot experiment. Yield of the test crop lettuce was also determined for all variants. RESULTS: Soil respiration was the most significantly increased property, positively affected by digestate + Humac. Both digestate + biochar and digestate + Humac significantly increased microbial biomass carbon. Significant negative effect of digestate + biochar (compared to the control digestate) on particular enzyme activities was alleviated by the addition of humic acids. No significant differences among the tested variants were found in the above-ground and root plant biomass. CONCLUSIONS: The tested organic supplements improved the digestate effect on some determined soil properties. We deduced from the results (carbon:nitrogen ratio, microbial biomass and activity) that the assimilation of nutrients by plants increased; however, the most desired positive effect on the yield of crop biomass was not demonstrated. We assume that the digestate enrichment with organic amendments may be more beneficial in a long time-scaled trial.