Influence of nutrient-challenged water on soil and forage quality
Clark, Donald Ray
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Declining fresh water sources could be countered with irrigation water from saline aquifers or industrial and municipal effluents but soil properties and forage quality may be affected. Greenhouse experiments were conducted in completely random designs with 4 replications to evaluate the effects of solute compromised secondary waters on soil properties and forage growth and quality. 'Dekalb FS-5' forage sorghum [Sorghum bicolor(L.) Moench] was grown with irrigation water of increasing salinities (1.7 to 12.2 dS m^-1). Accumulation of salts increased soil salinity and reduced soil pH. Concentrations of extractable soil Ca, Mg, Na, K, Mn, and Cd increased while S, Cu, and Fe decreased with increasing salinity. Sorghum survivability, growth, and water consumption decreased with increasing salinity. Concentrations of Ca, Sr, Mn, and Cd increased in sorghum while K, P, and S decreased with increased salinity. Two greenhouse experiments were conducted with seven water sources plus saline standards ranging in salinity from 0 to 8.3 dS m^-1 'Matua' bromegrass [Bromus willdenowii Kunth] was harvested 4 times with no leaching allowed. In the final experiment Dekalb FS-5 forage sorghum was harvested once with two leaching events. Soil NO3 and concentrations of extractable soil Ca, Mg, Na, K, and Sr were related to concentration of total-N and minerals in the secondary waters. Extractable soil Fe, Mn, and Zn were not closely related to amounts in the compromised or to changes to soil pH. Water infiltration rates varied and were most related to sodium adsorption ratios for the irrigation waters. Leaching of P was limited while leachate concentrations of Fe and Zn were greater than inputs through the irrigation water. Plant survivability and growth were most affected by salinity of the irrigation waters and accumulation of salts in soils. Plant N was increased linearly with increasing total-N in the irrigation waters. Concentrations of P, Cu, and Fe in Matua and sorghum could be inadequate for growing steers while Cd and K concentrations reached levels of concern for animal health with increased salinity. Interactions among constituents of wastewater, soil, and forages results in complexities not seen in simple solute systems.