PT  - JOURNAL ARTICLE
AU  - T.K. Iragavarapu
AU  - J.L. Posner
AU  - G.D. Bubenzer
TI  - The effect of various crops on bromide leaching to shallow groundwater under natural rainfall conditions
DP  - 1998 Apr 01
TA  - Journal of Soil and Water Conservation
PG  - 146--151
VI  - 53
IP  - 2
4099  - http://www.jswconline.org/content/53/2/146.short
4100  - http://www.jswconline.org/content/53/2/146.full
AB  - Information is limited on water and solute leaching in the presence of crops. This field investigation was conducted to determine the effect of various crops on leaching of a bromide (Br) tracer under natural rainfall conditions. The soil is a Griswold silt loam (fine-loamy, mixed, mesic, Acquic Argiudoll). Monitoring wells (4-m deep) to groundwater were installed in the center of a Br -treated area (5 m × 5 m) in selected plots planted to corn, soybean, and alfalfa. Bromide was surface-applied at the ratc of 197 kg ha−1 in May 1991. Dry weather conditions early in the growing season resulted in the formation of deep cracks in the field in all plots. Bromide was detected in the soil to a 80-cm depth by August (less than three months after application) under all the crops with only 1/0 mm of accumulated rainfall. This was presumably due to transport of Br through the soil cracks during the sporadic rainfall events. Simulation analysis with the Groundwater Loading Effects of Agricultural Management Systems (GLEAMS) computer model indicated that piston-flow was no adequate to provide the observed leaching depth of Br by the August sampling date. By November, Br was distributed fairly uniformly throughout the 1-m profile in all the treatments. Except in the top 20 cm, Br concentrations were significantly greater with the drilled soybean treatment compared to others at all depths. Crop uptake of Br was significantly greater (P 0.05) for corn (19.3 kg ha−1) and soybean (16 kg ha−1) compared to alfalfa (6.6 kg ha−1) or oats (4.5 kg ha−1). Bromide recovery (soil+tissue) was highest with the drilled soybean treatment (84%) followed by alfalfa (46%), corn (39%), and row soybean (28%) treatments in November. Monitoring wells sampled in December 1991 showed detectable amounts of Br in all the plots irrespective of the type of crop grown. Results from this study show that although the amount of Br recovered (soil+tissue) varied with the type of crop grown, Br breakthrough to groundwater occurred within one growing season under all crops. This is especially true when surface-applied Br moves rapidly through the soil via preferential pathways like macropcres. Greater potential for shallow groundwater pollution by non-adsorbed agri-chemicals exists on these medium-textured silt loam soils than previously believed.