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Water and Nitrogen Budget Dynamics for a Maize-Peanut Rotation in Florida

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan www.asabe.org

Citation:  Transactions of the ASABE. (in press). (doi: 10.13031/trans.13916) @2020
Authors:   M . I. Zamora Re, Sagarika Rath, Michael D. Dukes, Wendy Graham
Keywords:   Agricultural best management practices (BMPs), N leaching, Maize-peanut rotation, Bare fallow, Sensor-based irrigation scheduling, N fertilization, N balance, Water balance, sandy soils.

Highlights

DSSAT simulations of final N uptake, biomass, and yield for a three irrigation by three N rate rotational field experiment had good performance for the irrigated treatments (average nRMSE 9%) but greater error for the rainfed treatments (average nRMSE 15%)

Experiments and DSSAT simulations demonstrated that N fertilizer and irrigation applications were reduced by 26% and 60%, respectively when using a 247 kg N/ha fertilizer rate and a sensor-based irrigation schedule rather than conventional practices of 336 kg N/ha and a calendar-based irrigation method, with no impact on yield

Simulations demonstrated that N leaching during the crop rotation was reduced 37% when an N fertilizer rate of 247 kg N/ha and sensor-based irrigation scheduling was used versus conventional practices

Soil N increased (≥15 mg/kg) when maize and peanut residues decayed, then leached during the fallow season. Cover or cash crops planted immediately after the maize and peanut harvests have the potential to take up this N and reduce leaching

Abstract. Nitrogen (N) is an essential element for crop growth and yield; however, excessive N applications not taken up by crops can result in N leaching from the rootzone, increasing loads to waterbodies, and leading to a host of environmental problems. The main objective of this study was to simulate water and N balances for a three irrigation treatment by three N fertility rate treatment maize-peanut (Zea mays L. - Arachis hypogaea L.) rotational experiment. Irrigation treatments consisted of GROW, mimicking grower irrigation practices in the region; SMS, using soil moisture sensors to schedule irrigation; and NON, non-irrigated. The three N fertility rates evaluated were low, medium, and high (157, 247, and 336 kg N/ha, respectively for maize with a constant 17 kg/ha for all peanut treatments). DSSAT maize genetic coefficients were calibrated using the SMS-high experimental data treatment under the assumption of no water or N stress. The other eight treatment combinations were used as independent data for model validation of these crop coefficients. All soil hydrologic parameters were specified based on measured values and default DSSAT peanut genetic coefficients were used with no calibration. For irrigated treatments, DSSAT models had good performance on N uptake, biomass, and yield (average nRMSE 8%) and moderate performance on soil water content (average nRMSE 18%). Soil nitrate RMSE was 21% lower than the standard deviation of the observed data (5.8 vs. 7.2 mg/kg). For rainfed treatments DSSAT had greater error (average nRMSE 15% for N uptake, biomass, and yield, average nRMSE 31% for soil water, and soil nitrate RMSE was 11% greater than the standard deviation of the observed data (8.0 vs. 7.2 mg/kg) and nRMSE >30% during the crop rotation). Simulations estimated that N leaching over the crop rotation was reduced by 24% on average when using a rate of 247 kg N/ha compared to 336 kg N/ha across the irrigation treatments evaluated. Furthermore, N leaching was reduced 37% when using SMS to schedule irrigation and a 247 kg N/ha fertilizer rate in maize and 17 kg N/ha in peanut compared to conventional practices (GROW and 336 kg N/ha in maize and 17 kg N/ha in peanut). Moreover, following this management practice reduced N fertilizer use by 26% and irrigation water use by up to 60% without negative impacts on yield. Observed and simulated soil N increased during maize and peanut residue decay, with simulations estimating that this soil N would leach below the root zone during the fallow season. This fallow season leaching could potentially be reduced if a cover crop or a cash crop were planted between the maize and peanut crops to take up the mineralized N.

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