WWW.WAS.ORG • WORLD AQUACULTURE • SEPTEMBER 2015 67 This demonstration project addressed two questions: • Corn planted late in the growing season requires irrigation, but does irrigation water pumped from commercial channel catfish ponds contain enough nutrients to benefit corn production? • Does the volume of replacement groundwater improve water quality or increase catfish production in a pond used for irrigation compared to a static pond? Ponderosa Farms is located near Murray, in western Kentucky and produces corn, soybeans, wheat and channel catfish. In three fields with poorly drained soils that were not well suited for grain production, nine levee-type commercial catfish ponds were constructed, ranging from 1.6 to 2.0 ha. Each location contains three ponds that are filled with water from a 50-m deep well with a pumping capacity of 2.3 m3/min. Each pond is equipped with an electric, 10-hp, paddlewheel aerator. During summer, one pond in each location is used to supply water for crop irrigation. A water pumping truck equipped with an irrigation pump with a 15-cm intake and a 7.6-cm discharge capacity was connected to a field irrigation system. The pump trailer is powered by a truck-mounted 99-hp, 4-cylinder diesel engine that provided power to the irrigation pump and a 480 V, 3-phase electric generator that supplied electricity to center pivot field irrigation systems. The portable pumping station was constructed to reduce water pumping cost and increase pumping efficiency by locating the source of irrigation water closer to crop fields. Otherwise, irrigation water would have to be pumped to fields located far from the well. Late-summer corn was planted in the stubble of a harvested winter wheat crop in mid-June 2014. Irrigation water was pumped Irrigating Late Summer Corn with Channel Catfish Pond Water in Western Kentucky: A Demonstration Project Forrest Wynne, John Murdock and Rick Murdock from a 1.7-ha commercial channel catfish pond and applied to 13.9 ha of an 18.7ha field of yellow corn. A 247-m center-pivot irrigation system equipped with a terminal spray gun delivered pond water during seven watering trips between early July and mid-September. The system was calibrated to deliver 1.5 cm of water per ha of corn, or about 2,100 m3 per field application. One water application was estimated to be equivalent to approximately 8 percent of the catfish irrigation pond volume. Replacement water was pumped a short distance to the catfish irrigation pond from a nearby well. A 1.64ha catfish pond located next to the irrigation pond was used as a comparison. Weekly water samples were taken from both ponds during 11 weeks of irrigation. Comparisons were made between the irrigation and control pond to evaluate differences in water quality that may affect fish production and to estimate the amount of nutrients supplied to corn from pond water. Irrigation water suitability analyses were performed by a commercial agricultural laboratory. Rainfall was 17.8 cm between corn planting in mid-June and harvest in late October 2014. Ammonium nitrate (34-0-0) fertilizer was applied to emergent corn by spreader truck at 564 kg/ha in early July. Both ponds were stocked with 14,800 channel catfish per ha and were harvested and restocked in a multiple batch production system. Catfish were fed a floating, 28-percent protein, commercial catfish feed at 84 kg/ha per day. Dissolved oxygen concentration was monitored daily and nighttime aeration was provided when dissolved oxygen concentration fell below 3 mg/L. (CONTINUED ON PAGE 68) TABLE 1. Mean (± standard deviation) of water quality parameters of an irrigation pond and a catfish pond. Asterisk indicates a significant difference (P<0.05). Irrigation Control Pond Pond Nitrogen (mg/L) 5.2 (2.1) 4.7 (1.9) Phosphorus (mg/L) 0.23 (0.17) 0.33 (0.21) Potassium (mg/L) 6.2 (1.7)* 10.1 (2.3)* Calcium (mg/L) 5.0 (0.6) 5.3 (0.9) Magnesium (mg/L) 2.1 (0.4)* 2.7 (0.5)* Sodium (mg/L) 8.4 (1.3)* 7.0 (1.7)* Chloride (mg/L) 15.6 (5.6) 12.7 (4.7) Sulfate (mg/L) 5.8 (1.7) 7.6 (2.4) Boron (mg/L) 0 (0) 0.02 (0.01) Carbonate (mg/L) 0 (0) 0 (0) Bicarbonate (mg/L) 38 (14) 39 (13) pH 6.5 (0.2) 6.5 (0.2) Conductivity (mmhos/cm) 0.097 (0.004) 0.100 (0.010) Total dissolved solids (mg/L) 61 (3) 64 (7) Sodium absorption ratio (mg/L) 0.80 (0.16)* 0.62
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