Economic evaluation of silage crops under reduced irrigation in the Texas High Plains
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Agriculture production remains a major mainstay of the Texas High Plains economy. However, the primary groundwater source (Ogallala Aquifer) that supports the intensive nature of irrigated agriculture and livestock operations is waning rapidly which raises alarm for future sustainability of agriculture production in the area. The main goal of the study is to analyze the economic feasibility of corn silage and sorghum silage under reduced irrigation in the Texas High Plains. The specific objectives were to: 1) Estimate water response function for irrigated corn silage and sorghum silage. 2) Use the input response function to determine optimum levels of input to maximize profit for corn silage and sorghum silage production. 3) Perform a comparative analysis of water use between corn silage and sorghum silage and estimate potential water savings. 4) Predict the effect of forage quality of corn silage and sorghum silage on milk yield per ton of forage dry matter. Data for sorghum silage were obtained from the Texas AgriLife Research Center in Amarillo, Texas from sorghum silage trials 2007 to 2014 whereas corn silage data were obtained from 2009 to 2013 corn silage trials from the State Silage Corn Performance Test at Etter. Models were developed to determine the effect of water on corn silage and sorghum silage yield. These models were further used to determine the optimal input levels of total available water and applied irrigation water to maximize profit. The R2 value from the restricted model relating corn silage and sorghum silage to total available water received explained 99% and 97% of the variation in yield, respectively. The profit for irrigated sorghum silage ($43/ton) and irrigated corn silage ($48/ton) in the Northern Texas High Plains are $183/acre and $471/acre, respectively, at a natural gas price of $4/Mcf whereas the Southern Texas High Plains, had $242/acre and $554/acre, respectively, at electricity price of $0.074/kWh. A total of 258,068 acre-feet of water will be needed to produce 4,180,711 tons of corn silage whereas 239,692 acre-feet of water will be required to grow 4,646,340 tons of sorghum silage to meet the feed (silage) requirement of dairy cows in the Texas High Plains. The amount of water saved if corn silage is replaced by 50% irrigated sorghum silage and 50% dryland sorghum silage is 138,222 acre-feet. Crude protein, in-vitro true digestibility, starch, and lignin content of corn silage forage quality explained 99% of the variation in milk yield while sorghum silage forage quality explained 98%. Although there is 16% increase in milk yield in favor of corn silage due to forage quality, it is economically profitable to feed the dairy cows with sorghum silage as far as buying or growing both silages to formulate ration for dairy cows are concerned. The production cost of corn silage in the feed component of dairy cows is 15% more than sorghum silage per year. Improvement in crude protein, in-vitro true digestibility, and starch content of sorghum silage will increase the quantity of milk produced per ton of forage dry matter. Considering global concerns on water scarcity coupled with unpredictable climate changes, it is economically prudent to consider sorghum silage especially in the Texas High Plains where the groundwater (Ogallala Aquifer) is waning.