Effects Of Water Table Management Research Articles

Effect of water-table management and nitrogen supply on yield, plant growth and water use of corn in undisturbed soil columns

The effect of three water-table depths (30, 60 and 80 cm below the soil surface) and four N rates (0, 45, 90 and 135 kg ha−1) on plant growth, yield and water use were evaluated for corn (Zea mays L.). Research was conducted in a greenhouse, using 36 undisturbed foil columns (20 cm i.d. and 90 cm length) collected with a Meta-Drill vibrating core sampler from a Fox sandy loam soil at Harrow Research Centre. Corn grown in the 80-cm water-table depth had the greatest degree of water stress, as indicated by low volumetric soil water content, low stomatal conductance and transpiration rates, and elevated soil-surface and leaf-surface temperatures. There was a substantial increase in plant dry weight and grain yields as the N rates increased from 0 to 135 kg ha−1 with the 30- and 60-cm water-table depths. Under our experimental conditions, maximum grain yields were obtained with a 60-cm water-table depth. Grain yields were significantly reduced with the 80-cm water-table depth. With this water-table depth, grain yield was also reduced by N addition. Key words: Water-table management, Zea mays, yield, stomatal conductance, leaf temperature

Effect of Water Table Management on the Fate of the Pesticide Aldicarb

The fate of agricultural chemicals applied to cultivated fields with subsurface drains is an environmental concern. The transport of the pesticide aldicarb in the soil and groundwater in an agricultural field with subsurface drains was simulated using the computer model VS2DT. A Portsmouth soil from Plymouth, North Carolina, was simulated with five water table management treatmentsconventional or free drainage, controlled drainage, subirrigation, free drainage with surface irrigation, and controlled drainage with surface irrigation. Five drain spacings, 15.2, 22.8, 30.4, 38.1, and 45.7 m, were investigated. Two aldicarb degradation rates, 7- and 30-day half life, were simulated. Free drainage with surface irrigation produced the highest predicted aldicarb losses for all drain spacings while the controlled drainage treatment without surface irrigation consistently resulted in the lowest amount of aldicarb lost through tile outflow.

Water Table Management Effects on Denitrification and Nitrous Oxide Evolution

AbstractPrevious research suggested that using controlled drainage to elevate the water table reduces NO3− contamination of surface water by enhancing denitrification. The C2H2 inhibition technique was used to study denitrification and N2O evolution using 56‐cm‐long, undisturbed cores of Cape Fear loam (clayey, mixed, thermic Typic Umbraquult) maintained in the field and subjected to three static water table levels (15, 30, and 45 cm). Results showed that intermittent C2H2 exposure did not (i) affect soil inorganic N distribution between NH4+ and NO3−, (ii) diminish inhibition of N2O reduction during subsequent C2H2 exposure, or (iii) induce C2H2 decomposition. Denitrification from 1 Nov. 1993 through 21 Apr. 1994 (172 d) was 341 kg N ha−1 for the 15‐cm water table treatment, 260 kg N ha−1 for the 30‐cm water table treatment, and 86 kg N ha−1 for the 45‐cm water table treatment. Denitrification was maximum at the lowest monitored zone (36–54 cm) for each water table treatment. Total N2O evolution was 9 kg N ha−1 for the 15‐cm water table treatment, 4 kg N ha−1 for the 30‐cm water table treatment, and 2 kg N ha−1 for the 45‐cm water table treatment. Nitrous oxide evolution was positively correlated with mean soil temperature (10‐cm depth) until low NO3− levels appeared to limit denitrification. Since steady‐state diffusion was not reached, estimates of N2 evolution, using N2O evolution in the presence of C2H2, were underestimated 12‐fold. Evolved N2O‐N represented only 2% of denitrification in the soil core (0–54 cm) for each water table treatment. Drainage control to elevate the water table enhanced denitrification and N2O evolution, reducing the potential for N transport with subsurface drainage to surface water.

Predicting effects of water table management on loss of nitrogen from poorly drained soils

Agricultural drainage and related water management practices affect the quality and quantity of water leaving the field and entering ground and surface waters. The design and management of drainage systems should consider these impacts, as well as effects on agricultural production. In many instances, water quality and environmental requirements have a priority greater than that of maximizing agricultural productivity and profits. This paper describes the application of a simulation model, DRAINMOD-N, to predict the effects of design and management of subsurface drainage systems on nitrogen losses and crop yields. DRAINMOD-N uses hydrologic predictions by DRAINMOD, including daily soil water fluxes, in numerical solutions to the advective-dispersive-reactive (ADR) equation to describe movement and fate of NO3-N in shallow water table soils. Simulations were conducted for maize production on a Portsmouth sandy loam soil (Thermic, Typic Umbraquult) in the North Carolina Coastal Plain. Agricultural production objectives could be satisfied with 1 m deep parallel drains spaced 40 m apart or less. Predicted losses of NO3-N were significantly affected by drainage design and management. Increasing drain spacing from 20 to 40 m decreased NO3-N losses by 47 per cent. Nitrate losses can be further reduced by placing a weir in the drainage outlet so as to raise the water level in the outlet and reduce subsurface drainge rates. This practice, called controlled drainage, can be applied in both the growing season and the nongrowing season, and can be varied in intensity (with season) by placing the weir closer to or further below the soil surface. Controlled drainage during both the growing season and winter months reduced NO3-N losses from an annual average of 21.8 kg ha−1 to 10.5 kg ha−1 (52 per cent) for a 30 m drain spacing, without reducing crop yields.Analysis of simulated results on a year-by-year basis showed that large losses of NO3-N via drainage water occur in years following droughts when crops remove little of the fertilizer N because of reduced yields. Losses to the environment under these circumstances can be reduced by increasing the intensity of drainage control to minimize subsurface drainage during the following year. In one year, for example, raising the weir in the drainage outlet to a 25 cm depth directly after harvest and holding it there until time for seedbed preparation (one month prior to planting) in the spring reduced predicted NO3-N losses by 77 per cent compared to conventional drainage and by 60 per cent compared to currently recommended controlled drainage practices. The effectiveness of intensive drainage control was not as great in other years, but reduced NO3-N losses by at least 20 per cent in the years analysed. Results of this study indicate simulation modelling can be used to design and guide the management of drainage systems to address both agricultural productivity and environmental objectives.