Water‐Yield Relations of Several Spring‐Planted Dryland Crops following Winter Wheat

A winter wheat (Triticum aestivum L.)‐fallow cropping system has developed in the central Great Plains as a means to stabilize crop production in a highly variable climate. As an alternative, a flexible cropping system partially based on soil water at planting may allow producers to minimize risk while allowing some additional crop production during wetter climate cycles. Water‐yield relations are critical in the development of flexible cropping systems. The experiment was conducted near Sidney, NE, on a Keith silt loam (fine silty, mixed mesic Aridic Argiustoll) to determine the response of five spring‐planted crops (corn (Zea mays L.), grain sorghum [Sorghum bicolor (L.) Moench], pinto bean (Phaseolus vulgaris L.), proso millet (Panicum miliaceum L.), and sunflower (Helianthus annuus L.)) to three different soil water levels the year following winter wheat harvest. Water use of all crops increased with increasing soil water at planting. The grain yield of pinto bean and proso millet responded positively to soil water at planting. Soil water at planting accounted for less than half of the total variability in grain yield for corn, grain sorghum, and sunflower. Soil water at planting appears to be useful in determining the success of planting the two short duration crops (pinto bean and proso millet) the year after winter wheat harvest. For the long duration crops (corn, grain sorghum, and sunflower) other factors, such as precipitation near the time of flowering, may be more important in determining success. Research Question Dryland farmers in the semi‐arid central Great Plains are looking for alternative crops to complement their traditional winter wheat‐fallow rotations without significantly increasing production risk. This study was conducted to determine which alternative spring‐planted dryland crops had desirable soil water‐yield relations that might allow reasonable estimation of grain yields based on soil water at planting. Crops exhibiting a strong correlation between grain yield and soil water at planting could be used in a flexible cropping system to intensify cropping frequency while minimizing drought risk associated with more frequent cropping in the semi‐arid Great Plains. Literature Summary The central Great Plains is characterized by a continental climate with large year‐to‐year variation in precipitation. A flexible system of cropping, referred to as Flexcrop, has been proposed for the spring wheat production region of the northern Great Plains. The quantity of stored soil water at seeding has been identified as the production factor most related to crop growth and grain yield. Grain crops typically have a critical growth period during the season when water demand is high. Drought at these times can be devastating to grain production. The critical periods for crops in this study are: corn, silking and tasseling stages; grain sorghum, early boot to dough stage; pinto bean, early pod filling; proso millet, blooming stage; and sunflower, mid‐flowering. Study Description This study was conducted in 1992 and 1993 at the High Plains Agricultural Lab near Sidney, NE. A lateral‐move irrigation system was used to establish low, medium, and high soil water levels at planting. Treatments: Low, medium, and high soil water levels at planting. Five spring‐planted crops no‐till seeded in winter wheat stubble: corn—Pioneer ‘3790’ pinto bean—‘Othello’ proso millet—‘Sunup’ Grain sorghum—DeKalb ‘X‐218’ Sunflower—Dahlgren ‘707’ Weeds were controlled by hand hoeing. Soil type: Keith silt loam with pH of 7.3 to 7.7 and organic matter content of 1.7 to 1.2%, respectively. Growing season temperatures and precipitation are presented in Fig. . Growing season precipitation and temperature at the High Plains Agricultural Lab near Sidney, NE, during 1992 and 1993. image Applied Question In which of the spring‐planted dryland crops does grain yield consistently respond to soil water at planting when no‐till seeded into winter wheat stubble? Grain yields of the short‐duration crops such as pinto bean and proso millet appear to consistently respond positively to increasing soil water at planting. The long‐duration crops such as corn, grain sorghum, and sunflower do not appear to consistently respond to increasing soil water at planting with increased grain yields. The correlation of grain yield to soil water at planting appeared to decrease as the days from planting to harvest increased (Fig. ). Perhaps for short‐duration crops, there might still be a substantial amount of initial soil water available at flowering—typically the critical period of water requirement. For long‐duration crops, however, much of the initial soil water may be used in stover production and not available for grain development. The long‐duration crops are also more likely to suffer from such adverse weather as hail and early freeze due to the length of their growing season. Association between days from planting to harvest and the relationship (correlation) between grain yield and soil water at planting for five spring‐planted dryland crops no‐till seeded into winter wheat stubble near Sidney, NE. image What are the management implications from these results? Farmers in the semi‐arid central Great Plains often state that if they have moist soil to a 3 ft depth they feel confident in planting dryland corn. Many farmers also believe proso millet requires just one good rain after planting to yield well. This study would suggest that for long‐duration crops like corn, grain sorghum, and sunflower other factors like growing season precipitation, especially near flowering, might be more important in determining success than is soil water at planting. Conversely, grain yield potential for short‐duration crops can be roughly estimated based on soil water at planting, therefore, management decisions such as crop to be planted and production inputs to be used may be made with at least some reasonable expectation of outcome. Bear in mind that the above conclusions are drawn from a limited a set in which no drought conditions occurred. Therefore, the above discussion is probably best limited to situations of moderate to ample soil water conditions at planting.