Alan Schlegel

Equations for Drainage Component of the Field Water Balance

Accurate estimates of the drainage component of the field water balance are needed to achieve improved management of drainage in irrigated crop production systems and obtain improved estimates of evapotranspiration (ET) from soil water measurements. Estimating drainage for numerous soil and field conditions necessitates the use of simple, yet accurate, drainage equations containing easily measured parameters. The Wilcox drainage model is a relatively simple mathematical equation with a high degree of accuracy and applicability to field conditions. Our objectives were to develop Wilcox-type drainage rate equations for three coarse-textured soils of the west-central Great Plains and assemble previously determined, but fragmented, Wilcox-type drainage equations and supporting information for three medium-textured soils of the region. Drainage plots for collection of data for development of Wilcox-type drainage equations were established on two coarse-textured soil profiles in 2008 near Garden City, Kansas. Total water content of the soil profiles was measured over time during ~48-day drainage events. Total water was plotted against drainage time on log-log scales, and the linear regression equation relating the two variables was determined. These linear equations of profile water (log10) vs. drainage time (log10) were used to develop Wilcox-type drainage equations in which drainage rate (dW/dT in mm/day) is expressed as a function of soil profile water content (in mm). Drainage rate equations in this article can be used to estimate the drainage component of the field water balance for improved irrigation water management and more accurate estimates of ET from soil water measurements.

Application and Utilization of Livestock Effluent Through Sdi Systems

Abstract: Subsurface drip irrigation (SDI) can be successfully used for application of livestock effluent to agricultural fields with careful consideration of design and operational issues. Primary advantages are that exposure of the effluent to volatilization, leaching, runoff into streams, and humans can be reduced while the primary disadvantages are related to system cost and longevity, and the fixed location of the SDI system. An engineering study with beef feedlot effluent has indicated that driplines with discharge of 1.5 to 2.3 L/hr-emitter can be used successfully with little clogging. SDI tended to have greater corn yields and better nutrient utilization than low-energy precision application (LEPA) center pivot sprinklers when using swine effluent in a two-year field study.

Corn and Grain Sorghum Morphology, Physiology, and Phenology

Corn and grain sorghum are among the top cereal crops worldwide, and both are key for global food security. Similarities between the two crops, particularly their adaptation for warm-season grain production, pose an opportunity for comparisons to inform appropriate cropping decisions. A comprehensive comparison of morphological, physiological, and phenological characteristics for these crops is dated and limited. The objective of this chapter of the book was to investigate and document key morphological, physiological, and developmental characteristics of corn and grain sorghum in comparison to one another. Around 60 peer-reviewed journal articles, extension publications, books, and electronic resources were reviewed. Morphologically, grain sorghum and corn appear similar, at least above ground during their vegetative growth stages. Their physiology and developmental stages also are similar in resource-rich environments. Notable differences reported for the two crops in morphology, physiology, and phenology were related to their adaptation to different water stress conditions. Relatively, sorghum is more deeply and densely rooted, maintains physiological activities at higher levels than corn in lower water conditions, and has the plasticity to hasten or delay phenological events under drought stress conditions. Corn tends to have taller stalks and relatively more leaves, favoring greater yield in resource-rich environments.

Optimal Corn Management with Diminished Well Capacities

Many of the irrigation systems today in the Central Great Plains no longer have the capacity to apply peak irrigation needs during the summer and must rely on soil water reserves to buffer the crop from water stress. Considerable research was conducted on preseason irrigation in the US Great Plains region during the 1980s and 1990s. In general, the conclusions were that in-season irrigation was more beneficial than preseason irrigation and that often preseason irrigation was not warranted. The objective of this study was to determine whether preseason irrigation would be profitable with today’s lower capacity wells. A field study was conducted at the KSU-SWREC near Tribune, KS, from 2006 to 2009. The study was a factorial design of preplant irrigation (0 and 75 mm), well capacities (2.5, 3.8, and 5 mm day-1 capacity), and plant population (55,000, 68,000, and 80,000 plants ha-1). Preseason irrigation increased grain yields an average of 1.0 Mg ha-1. Grain yields were 29% greater when well capacity was increased from 2.5 to 5.0 mm day-1. Water use efficiency was not significantly affected by well capacity or preseason irrigation. Preseason irrigation was profitable at all well capacities. At well capacities of 2.5 and 3.8 mm day-1, a seeding rate of 68,000 seeds ha-1 was generally more profitable than lower or higher seeding rates. A higher seeding rate (80,000 seeds ha-1) increased profitability when well capacity was increased to 5 mm day-1.