Reevaluating On-farm Inputs in Corn and Forage Sorghum Silage Systems

Beef and dairy industries form the base of livestock production in New Mexico. In 2003, Curry, Roosevelt, and Chaves counties accounted for over 48% of all livestock cash receipts in the state (New Mexico Agricultural Statistics, 2003). Milk is the state’s number one cash commodity, producing over $790 million in 2003; and these three counties accounted for over 63% of milk cow numbers and milk cash receipts (New Mexico Agricultural Statistics, 2003). Cattle numbers are increasing in the area because of recent influxes of dairy operations from other parts of the U.S. It is important to conduct research that is applicable to the dairy industry because it has such a large influence on the agricultural and economic stability of communities in the area. Forages provide valuable, low-cost feeds that often result in excellent animal weight gains and milk production with a high net return on investment; and forages comprise the majority of dairy feeds. Warm-season annual grasses used as silage and greenchop in dairy and beef feedyard rations are well adapted to the climatic conditions of the Southern High Plains. Of these, corn (Zea mays L.) is used most extensively in feeding programs as a feedsource for lactating dairy cows which need high energy feed for maximum milk production. Corn production, however, requires relatively large amounts of water in order to be high yielding and of adequate nutrition for the dairy industry. It has been documented that forage sorghums [Sorghum bicolor (L.) Moench] have the potential to produce as much, and in some cases more, dry matter than corn when grown with the same amount of water. Although dependent upon many environmental and management conditions, productivity of forage sorghum, if managed properly, can be as productive and feed-valuable as corn. Just as widely accepted is the assertion that, in general, sorghums are more water-use efficient than corn and require less water to produce a certain amount of dry matter. Even in situations where corn and sorghum water-use efficiencies are similar, corn tends to use more water because of earlier planting dates and longer growing seasons. In addition to the advantage of a later planting date, forage sorghums have the ability to maintain high yields under water stress conditions and resume growth after drought. Several opportunities exist to utilize these forages for livestock, including grazing, ensiling, and cutting for hay; and the flexibility of management options makes them valuable and attractive to growers in regions of extreme climatic instability such as the Southern High Plains of the U.S. Historically, sorghum silage nutritive value has been inferior to that of corn silage due to low energy and digestibility of the ensiled product; and acceptance among dairies and feedyards has been limited. In more recent years, however, sorghum forage quality has improved through