Dryland Corn vs. Grain Sorghum in Western Kansas

Dryland crop yields in the U.S. Great Plains are limited by low precipitation and high potential evapotranspiration. In western Kansas wheat (Triticum aestivum L.) and grain sorghum [Sorghum bicolor (L.) Moench] are grown commonly, whereas corn (Zea mays L.) is believed to lack sufficient drought and heat tolerance for dryland production. A study was conducted near Garden City, KS, from 1991 through 1995 to determine whether corn could be grown successfully. No-till (NT) and conventional-till (CT) corn and grain sorghum were compared. In the driest year, sorghum yielded 137% more than corn with CT and 85% more with NT, but in 3 of 5 yr, NT corn yielded from 34% to 112% more than NT sorghum. In the remaining year, CT sorghum yielded more than CT corn, but NT yields did not differ. Overall, NT increased corn yields by 28% and net return by 69%, but increased sorghum yields by only 11% and had no effect on net return. No-till corn yielded 28% more than NT sorghum and produced 169% more net return, whereas CT corn yielded 11% more than CT sorghum and produced 48% more net return. Dryland corn can be grown in western Kansas if lower yields and returns are accepted in dry years in exchange for yields and returns considerably higher than those of sorghum in favorable years. No tillage will substantially increase yields in most years and is essential to assure adequate corn yields in dry years. Research QuestionMost acres of dryland corn in the western Great Plains are in western Nebraska, with significant acreage in northwest Kansas and northeast Colorado. Grain sorghum is the summer crop grown commonly. Temperatures and potential evapotranspiration increase from north to south in the Great Plains, and western Kansas, particularly the southwest, traditionally has been considered too hot and dry for dryland corn. However, farmer interest in dryland corn is increasing, and some farmers have successfully grown it in southwest Kansas in years of favorable climatic conditions. No research has been published from the western part of the state directly comparing corn and grain sorghum. No study has proven that even if dryland corn produced adequate yields, that grain sorghum would not produce more grain in the same field. Therefore, a study was conducted to compare dryland corn and grain sorghum. The objective of this study was to determinine if dryland corn can be grown successfully in southwest Kansas. Literature SummaryWheat-fallow is the most common dryland cropping system in the Great Plains. This system allows a crop to be harvested on the same land every other year. Wheat-sorghum-fallow results in two crops in 3 yr and produces more grain and profit than wheat-fallow, particularly when combined with reduced or no tillage (NT). Grain sorghum in rotation with wheat uses the additional stored water of NT and produces a yield increase more often than wheat. No-till dryland corn in a wheat-corn-fallow system has been successful in the northern areas of the central Great Plains, but has not been grown on significant acres further south than northwest Kansas because of a perceived lack of heat and drought tolerance. Study DescriptionThe study was conducted at the Southwest Research Extension Center near Garden City, KS, from 1991 through 1995. The soil type was a Ulysses silt loam having a pH of 7.8 and an organic matter content of 1.5%. Long-term climatic data for Garden City are: preciptation 17.91 in.; mean temperature, 53°F; open pan evaporation (April– September), 67 in.; and frost-free period, 169 d. Corn and grain sorghum were grown in the wheat-row crop-fallow system at populations of 18 000 and 25 000 plants/acre, respectively. Corn was planted on approximately 1 May of each year, whereas sorghum was planted in late May to early June. Conventional (sweep) tillage (CT) and NT were compared. Applied QuestionsWhy would a farmer grow dryland corn? Corn has a higher yield potential than grain sorghum. Corn and sorghum are both feed grains. Feedlots in the Great Plains prefer corn to grain sorghum because it is more digestible with less processing. Therefore, corn brings a higher price. Also, many more herbicides are labeled for weed control in corn. This is particurly true for johnsongrass and shattercane. Grain sorghum cannot be grown successfully in many fields because of competition from these species. What are the disadvantages of growing dryland corn rather than grain sorghum? Corn does not produce as much grain as sorghum under hot, dry conditions. Dry weather results in reduced yields of both crops, but corn is affected more than sorghum. What were the results of the study? No-till corn yielded an average of 22 bu/acre (28%) more than NT grain sorghum (Table 1). No-till corn yields significantly exceeded NT sorghum yields in 3 of 5 yr and were less than sorghum yields only in the driest year of 1991. Conventional till corn yields exceeded those of sorghum in 2 yr and were less than sorghum yields in 2 yr. No tillage increased corn yields in 4 of 5 yr, whereas NT increased sorghum yields in only 2 yr. The only year not favorable for corn production was 1991, when NT sorghum yielded 85% more than NT corn, and CT sorghum yielded 137% more than CT corn. Using the crop prices in effect during this study, NT dryland corn returned $46/acre more than NT dryland grain sorghum. If farmers can accept less yield and income in dry years in exchange for substantially more grain and income in favorable years, then corn can be a viable alternative to grain sorghum in southwest Kansas. Are the results of this study only for southwest Kansas or can they be applied to a larger area? Since the main problems with dryland corn are lack of heat and drought tolerance, the results of this study certainly apply to areas Further north, such as northwest Kansas, southwest Nebraska, and northeast Colorado, where there is already a large acreage of dryland corn. In fact, recommendations based on this research may be slightly conservative for these areas. In drier areas, such as southeast Colorado, and areas of higher potential evapotranspiration, as in the Oklahoma and Texas panhandles the results of this study should be implemented with caution, i.e. more research is needed in these areas. Table 1Yield of dryland corn and grain sorghum 89 affected by tillage, 1991–1995. 19911992199319941995AverageCropCT†NTCTNTCTNTCTNTCTNTCTNT----------------------------------------bu/acre----------------------------------------Corn19341431488598741187711080102Sorghum45631011039793698850527280†CT = conventional tillage, NT = no tillage.