Retired, Emeritus Professor, Dr. Aiken’s research goal was to contribute knowledge of factors regulating the crop transpiration fraction of the annual water budget and the transpiration efficiency of yield formation for water-limited cropping systems. The NWREC Crops Program maintains long-term cropping system studies to evaluate cropping intensity and tillage effects on water use, yield formation and critical soil properties. Field instrumentation quantifies canopy formation, thermal indices of water stress and photosynthetic/transpiration relationships. Support for sorghum and wheat breeding is provided through the development of high-throughput screening tools to efficiently identify crop water productivity, cold tolerance and heat tolerance traits. Agronomic support for sunflower breeding focuses on pest-resistance and pest management traits.
Sustainable cropping systems (WKARC Research Goal 3)
Crop rotations, tillage and fallow-replacement studies compare management effects on effective water capture, crop canopy formation, above-ground biomass productivity and yield formation.
Cropping intensity: Under multi-year drought conditions, wheat-fallow (one crop in two years) and wheat-grain sorghum-fallow (two crops in three years) cropping systems maintained land productivity and positive economic returns to land and management. Increasing crop intensity by replacing fallow with spring canola, soybean or sunflower increased the crop transpiration fraction of the annual water budget. However, crop water productivity was reduced, due to reduced available soil water. The practice of summer fallow, prior to drilling wheat in fall, remains viable—particularly under drought conditions. Spring oilseed crops provide opportunity for more intensive cropping with favorable soil moisture conditions.
- Ten crop sequences, transition to no-till (PDF). 2008. R. Aiken and D. O’Brien. Proc. Cover Your Acres Winter Conference. Oberlin, KS.
Wheat water productivity: Replacing fallow with oilseed crops (spring canola, soybean or sunflower) reduced water productivity of wheat (ratio of grain yield to crop water use). Continuous cropping reduced available soil water, above-ground biomass growth and harvest index (ratio of grain to above-ground biomass), compared to that of wheat following an 11-month fallow period. Eliminating fallow, in the semi-arid U.S. High Plains, diminished water use and crop water productivity of the subsequent wheat crop.
- Replacing fallow with continuous cropping reduces crop water productivity of semiarid wheat (PDF). 2013. R. Aiken, D. O’Brien, B. Olson, and L. Murray. Agron. J. 105:199-207.
Spring oilseed crops: Productivity of spring oilseed crops (canola, Indian Brown Mustard, Camelina) is favored by early to mid-March planting and stand establishment for early flowering.
- "Planting methods affect emergence, flowering and yield of spring oilseed crops in the U.S. central High Plains” R. Aiken, D. Baltenspergerk, J. Krall, A. Pavlista and J. Johnson. Industrial Crops and Products 69 (2015) 273-277
- Planting date effects on spring oilseed production (PDF). 2010. R. Aiken, R. Wolf, L. Dible and A. Oien. Field Research Report of Progress SRP 1030, pp. 72-75
- Canola harvest methods (PDF). 2010. R. Aiken, R. Wolf, L. Dible and A. Oien. Field Research Report of Progress SRP 1030, pp. 83-84
Sunflower water productivity: Sunflower studies address crop water use, yield formation and support pest management research.
- Effects of planting period on sunflower productivity in Northwest Kansas (PDF). 2003. R. Aiken, and R. Stockton. KSU Agronomy Field Research, Report of Progress 913. pp. 97-98.
- Effects of supplemental water on sunflower productivity in Northwest Kansas (PDF). 2003. R. Aiken, and R. Stockton.KSU Agronomy Field Research, Report of Progress 913.
Sunflower pest management: Stem-infesting insect pests that affect sunflower yield formation and lodging can be managed by planting practices. These studies were done in collaboration with the USDA-Agricultural Research Service Sunflower Research Unit in Fargo, North Dakota.
- Impact of combining planting date and chemical control to reduce larval densities of stem-infesting pests of sunflower in the Central Plains (PDF). 2007. L. Charlet, R. Aiken, R. Meyer and A. Gebre-Amlak. J. Econ. Entomol. 100(4):1248-1257.
- Influence of planting date on sunflower stem weevil (Coleoptera: Curculionidae) larval density and parasitism in oilseed and confection sunflower in western Kansas (PDF). 2005. L. Charlet and R. Aiken. Crop Management. DOI: 10.1094/CM-2005-0812-01-RS.
- Impact of irrigation on larval density of stem-infesting pests of cultivated sunflower in Kansas. 2007. L. Charlet, R. Aiken, R. Meyer and A. Gebre-Amlak. J. Econ. Entomol. 100(5):1555-1559.
Sunflower pest resistance: Agronomic support for the ARS Sunflower Research Unit has shown that pest-resistant sunflower hybrids may be derived from germplasm showing resistance to stem and head pests.
- Resistance among cultivated sunflower germplasm to stem-infesting pests in the central Great Plains (PDF). 2008. L. Charlet, R. Aiken, J. Miller and G. Seiler. J. of Econ. Entomol. 102:1281-1290. (Document)
- Resistance in cultivated sunflower to the Sunflower Moth (Lepidoptera: Pyralidae) (PDF). 2008. L. Charlet, R. Aiken, G. Seiler, A. Chirumamilla, B. Hulke and J. Knodel. J. of Agric. & Urban Entomol. 25(4):245-257. (Document)
- Methods for assessing infestations of sunflower stem weevil, Cylindrocopturus adspersus LeConte (Coleoptera: Curculionidae), in sunflower stems. 2014. J.R. Prasifka, J. F. Campbell, R.M. Aiken and J.D. Bradshaw.The Canadian Entomologist. 146:465-469.
Support for irrigation management research addresses water use and yield formation of grain and oilseed crops.
Irrigating oilseed crops: Oilseed crops provide opportunity to diversify irrigation production systems and to adapt to limited irrigation pumping capacities. Oilseed yield responses to water use and opportunities to enhance productivity are reviewed. Sunflower can be a suitable crop for deficit irrigation, where pumping capacity is limited. Growing conditions can modify yield potential. Oil composition changes in relation to reproductive development.
- Oilseed crop water use and water productivity (PDF). 2011. R. Aiken, F. Lamm, and A. Aboukheira. Proc. 2011 Irrigation Association Tech. Conf., San Diego, California, November 6-8, 2011.
- Sunflower canopy and oilseed yield formation under deficit irrigation (PDF). R. Aiken, F. Lamm and G. Seiler. 2012. National Sunflower Association Research Forum. Fargo, N.D.
Predictive understanding of production systems (WKARC Research Goal 4)
Field studies quantify fundamental biological mechanisms which affect plant responses to management and environmental variables.
Sunflower development: The timing of sunflower leaf appearance and reproductive development is related to growing degree days, a measure of thermal time. Day-length during mid-vegetative growth also modifies the onset and duration of reproductive development, from flowering to maturity.
- Applying thermal time scales to sunflower development (PDF). 2005. R. Aiken. Agron. J. 997:746-754.
Canopy temperature: Crop canopy temperature can indicate crop water stress related to canopy restrictions in transpiration. Information about transpiration control can be gained from plant sensors and weather data. These studies indicate plants adjust transpiration to maintain efficient photosynthesis.
- Inferring transpiration control from sap flow heat gauges and the Penman-Monteith equation (PDF). 2012. R. Aiken and N. Klocke. Transactions of the ASABE. 55(2):543-549.
- Corn canopy temperature as a stress index with limited subsurface drip irrigation (PDF). 2005. R. Aiken and F. Lamm. Field Research Report of Progress SRP 956.
Sorghum productivity: The intrinsic productivity (above-ground biomass) of sorghum, with respect to light use, is similar to that of high-yielding corn hybrids. We dectected large genetic differences among sorghum cultivars with 60% greater productivity in the most productive compared to the least productive cultivars. Similar biomass productivity per unit of water used indicates the potential to increase sorghum water productivity by increasing crop growth responses to intercepted light.
- Water and radiation use efficiencies in sorghum (PDF). 2013. S. Narayanan, R. Aiken, V. Prasad, Z. Xin and J. Yu. Agron. J. 105:199-207. (Document)
- Genetic diversity of transpiration efficiency in Sorghum (PDF). 2009. Xin, Z., R.M. Aiken and J. Burke. Field Crops Research 111:74-80. (Document)
Research collaboration provides WKARC scientists with access to system scientists to develop and make use of computer models.
Kansas Water Budget: The Kansas Water Budget (KSWB) uses daily weather data and knowledge of soil-crop water processes to provide a realistic view of the soil water balance and grain yield for rain-fed wheat and grain sorghum in Western Kansas. The USDA Ogallala Aquifer Program supported development of a regional database to confirm and enhance the predictive accuracy of the Kansas Water Budget.
- Forecasting wheat and sorghum yields with the Kansas Water Budget (PDF). 2008. R. Aiken, L. Stone and A. Schlegel. Field Research Report of Progress SRP 1017, pp. 126-129
Yield Tracker: Remote sensing of crop canopy formation can contribute to yield forecasts. The predictive accuracy of the YieldTracker computer model for corn yield was acceptable for well-watered conditions.Improvements are required to forecast yields under water-limiting conditions.
- Evaluating YieldTracker yield forecasts for corn in western Kansas (PDF). 2009. P. Coyne, R. Aiken, S. Maas and F. Lamm. Agron. J. 101:671-680.
Drought assessment: A new study, supported by the Kansas Water Resources Institute, assembled a Kansas-wide database of monthly average temperature and total precipitation (80+ locations, 120 years). These records were used to analyze dynamic properties of drought indices (Palmer Drought Severity Index, Standardized Precipitation Index, and Standardized Precipitation Evapotranspiration Index) and to strengthen drought forecasting capabilities.
- Winter wheat yield responses to climate variation in the U.S. Central Great Plains. R. Aiken, X. Lin and Z. Zambreski. Written for presentation at the 2017 ASABE Annual International Meeting. DOI: https://doi.org/10.13031/aim.201701661
Cold tolerance: Traits needed for early-planted grain sorghum include rapid emergence and vigorous growth under chilling conditions, earlier flowering and desirable agronomic traits. High-throughput screening, under controlled environment conditions, is suitable for evaluating seedling emergence. Field confirmation is required for evaluation of seedling growth, flowering date and agronomic traits. Several sources for rapid emergence, seedling growth, and early flowering were identified.
- Analysis of sorghum [Sorghum bicolor (L.) Moench] lines and hybrids in response to early-season planting and cool conditions (PDF). 2013. M. Kapanigowda, R. Perumal, R. Aiken, T. Herald, S. Bean, and C. Little. Can. J. Plant Sci. 93:773-784.
- Genotypic variation in sorghum [Sorghum bicolor (L.) Moench] exotic germplasm collections for drought and disease tolerance (PDF). 2013 Kapanigowda, M.H., R. Perumal, M. Djanaguiraman, R. M. Aiken, T. Tesso, P.V.V. Prasad, C.R. Little. SpringerPlus 2:650.
Canopy productivity: Crop canopies provide the building blocks for plant growth, as well as the means for transpiration control. A simple canopy formation model is suitable for characterizing differences, among sorghum cultivars in leaf growth and development. New traits enhancing sorghum productivity include upright leaves for improved light utilization, limited transpiration under hot and dry conditions, and heat stress tolerance. Stay-green is a well-known trait which extends the duration of canopy function and supporting stalk strength under drought conditions. Remote sensing tools (digital cameras, small unmanned airborne systems) provide opportunity to detect these advanced productivity traits in crop breeder nurseries. Development of remote sensing tools for sorghum breeding is supported by the Kansas Grain Sorghum Commission.
- A simple quantitative model to predict leaf area index in Sorghum (PDF) S. Narayanan, R. Aiken, V. Prasad, Z. Xin and J. Yu. 2014. Agron. J. 106:219-226. (Document)
- A field procedure to derive heat, water vapor and carbon dioxide exchange rates from digital images of vegetative canopies. 2011. R. Aiken, R. P. Coyne and A. Aboukheira. Proc. ASABE Annual International Meetings. Louisville, Kentucky, August 7 – 10, 2011.
Adaptive traits in wheat
Wheat productivity: Recent studies show that laboratory analysis of wheat grain samples can provide useful information about crop water use efficiency (ratio of biomass produced to water used). These results may also provide information about plant nutrient supply and utilization. The Kansas Wheat Alliance is supporting research to evaluate wheat grain produced under well-watered, rain-fed and drought-stress growing conditions. The tests may provide a means of detecting cultivars with more effective root systems.
- Relationship between carbon isotope discrimination and grain yield of rainfed winter wheat in a semi-arid region. G. Zhang, R. Aiken and T.J. Martin. Euphytica (2015) 204:39-48.