Estimation of Nitrogen Pools in Irrigated Potato Production on Sandy Soil Using the Model SUBSTOR

Abstract

Recent increases in nitrate concentrations in the Suwannee River and associated springs in northern Florida have raised concerns over the contributions of non-point sources. The Middle Suwannee River Basin (MSRB) is of special concern because of prevalent karst topography, unconfined aquifers and sandy soils which increase vulnerability of the ground water contamination from agricultural operations- a billion dollar industry in this region. Potato (Solanum tuberosum L.) production poses a challenge in the area due to the shallow root system of potato plants, and low water and nutrient holding capacity of the sandy soils. A four-year monitoring study for potato production on sandy soil was conducted on a commercial farm located in the MSRB to identify major nitrogen (N) loss pathways and determine their contribution to the total environmental N load, using a partial N budget approach and the potato model SUBSTOR. Model simulated environmental N loading rates were found to lie within one standard deviation of the observed values and identified leaching loss of N as the major sink representing 25 to 38% (or 85 to 138 kg ha-1 N) of the total input N (310 to 349 kg ha-1 N). The crop residues left in the field after tuber harvest represented a significant amount of N (64 to 110 kg ha-1N) and posed potential for indirect leaching loss of N upon their mineralization and the absence of subsequent cover crops. Typically, two months of fallow period exits between harvest of tubers and planting of the fall row crop (silage corn). The fallow period is characterized by summer rains which pose a threat to N released from rapidly mineralizing potato vines. Strategies to reduce N loading into the groundwater from potato production must focus on development and adoption of best management practices aimed on reducing direct as well as indirect N leaching losses.

Influence of feedstocks and pyrolysis on biochar’s capacity to modify soil water retention characteristics

“…A combination of accelerated erosion processes (water, tillage, and wind) has modified many agricultural landscapes [42]. Severely eroded soils are frequently degraded in terms of their ability to supply water for crop production.…”

Environmental Nitrogen Losses from Commercial Crop Production Systems in the Suwannee River Basin of Florida

“…Information on regional geology, climate and soils can be found elsewhere [22]. Briefly, the farm lies along a physiographic region of Cody Escarpment where the sands are thick and the eroded Hawthrone formation consist of thin and pocketed clay to no clay atop the limestone.…”

Evaluation of the Performance of Different Organic Fertilizers on Maize Yield: A Case Study of Kampala, Uganda

“…The fertilizer was applied 3 weeks after planting, when all maize plants had fully emerged from the soil. According to Shisanya, Mucheru, Mugendi, and Kung'u (2009), potential nitrogen losses due to leaching are higher in the first few weeks after sowing, when evapotranspiration is low and also during this period plant roots are not sufficiently well developed to take up the available nitrates (Prasad, Hochmuth, & Boote, 2015). The fertilizer was spread, or sprayed in the case of digestate, in a ring around the plant and then covered with soil.…”