Water Quality Evaluations of Biochar in Cotton Production Systems in the Mississippi Delta

Investigators: Amrinder Jakhar, Gurpreet Kaur, Gurbir Singh, Saseendran Anapalli

Date: 2021

Project Summary

Introduction

Conventional tillage practices commonly followed in the Mississippi Delta cause soil compaction, deteriorate soil structure, reduce soil organic matter reserves, and consequently result in nutrient losses from the soil. Nutrient leaching from agricultural soils might increase soil acidity, add up fertilizer cost for farmers, and adversely affects the quality of surface and groundwater. Soil amendments such as biochar could be a potential solution to this issue. Biochar is a carbonaceous product obtained through the pyrolysis process by subjecting organic biomass to heat treatment (212-1292oF) either in the absence or limited availability of oxygen. The overall objective of this study was to evaluate the impact of sugarcane biochar amendment on nutrient leaching in dryland cotton production systems on Sharkey clay soil in the Mississippi Delta.

Materials and Methods

A field experiment was conducted at the USDA-ARS Crop Production System Research Unit’s farm in Stoneville, MS. The experiment was carried out in a completely randomized design with four replications. Each plot included 6 rows and the size of the treatment plot was 60 ft × 20 ft. Treatments included biochar application at rates of 0, 11, 22, and 44 tons/ ha. Two suction-cup lysimeters were installed in each plot at a depth of 18 and 32 inches to collect the soil solution samples. Soil solution samples were collected after every significant precipitation event (>0.25 inches). A total of 32 events of soil solution samples were collected from December 2019 to August 2021. After collection, soil solution samples were brought to the lab and analyzed for pH and electrical conductivity (EC) using the Fisherbrand pH Combination Electrodes (Chelmsford, MA) and Fisherbrand Four Cell conductivity probe (Chelmsford, MA), respectively. The soil solution samples were then vacuumed filtered using a 0.45-micrometer filter and were analyzed for anions including nitrite-N (NO2-N), Nitrate-N (NO3-N), fluoride (F-), chloride (Cl-), phosphate-P (PO4-P), and sulfate- S (SO4-S) using the Dionex Integrion High Pressure Ion Chromatograph (Sunnyvale, CA) and for ammonia (NH4-N) using Lachat 8400 series II automated ion analyzer (Hach Corp., Loveland, CO). The GLIMMIX procedure in SAS software (version 9.4) was used for analyzing the data.

Results and Discussion

Biochar application rate had a pronounced effect on nitrate and phosphate level of the soil (Figure 1). Nitrate and phosphate concentration in soil solution declined by 26 to 66% and 11 to 31%, respectively, with the increasing rate of biochar application compared to the control plots (0 ton/ha). Fluoride concentration in soil solution increased by 9% with biochar application at the rate of 44 ton/ha than the control plots. Nitrite-N reduced by 13% and 35 % at 18 and 36 inches depth, respectively, with biochar application at 44 ton/ha (Table 1) compared to control plots. Reduced leaching of nutrients with the addition of biochar was due to the increase in cation exchange capacity of soils. For biochar application rates at 22 and 44 ton/ha, the electrical conductivity for soil solution samples was lower in the deeper soil layer (32 inches) than at the 18 inches depth (Table 1). There was a higher buildup of SO4-S at 18- inch depth with biochar applied at the rate of 22 and 44 ton/ha.

Conclusion

Biochar application confirmed a reduction in nutrient leaching losses, viz. nitrate, chloride, and phosphate. In the present study, the application of 44 ton/ha biochar indicated the maximum reduction in leaching of nitrate, phosphate, and chloride in soil solution. However, the biochar application rate of 11 ton/ha may be more economical, with sufficient reduction in nutrient leaching in dryland cotton production systems over time.

Project Photos

• Crop Type:
• Cotton

• Topic:
• Irrigation Scheduling
• Technologies
• Soil