38 research outputs found
Evaluation of the Doraiswamy-Thompson winter wheat crop calendar model incorporating a modified spring restart sequence
The Robertson phenology was used to provide growth stage information to a wheat stress indicator mode. A stress indicator model demands two acurate predictions from a crop calendar: date of spring growth initiation; and crop calendar stage at growth initiation. Several approaches for restarting the Robertson phenology model at spring growth initiation were studied. Although best results were obtained with a solar thermal unit method, an alternate approach which indicates soil temperature as the controlling parameter for spring growth initiation was selected and tested. The modified model (Doraiswamy-Thompson) is compared to LACIE-Robertson model predictions
Irrigation and Fertilization Practices for Seed Production from Established Stands of Side-oats Grama
The objectives of this study of grass seed production were to determine the response of an established stand of a warm-season grass to irrigation and fertilizer practices with regard to the specific practices needed to produce maximum quantity of adequate quality seed per acre. Side-oats grama was chosen for the study because of the availability of adapted varieties
Winter wheat: A model for the simulation of growth and yield in winter wheat
The basic ideas and constructs for a general physical/physiological process level winter wheat simulation model are documented. It is a materials balance model which calculates daily increments of photosynthate production and respiratory losses in the crop canopy. The partitioning of the resulting dry matter to the active growing tissues in the plant each day, transpiration and the uptake of nitrogen from the soil profile are simulated. It incorporates the RHIZOS model which simulates, in two dimensions, the movement of water, roots, and soluble nutrients through the soil profile. It records the time of initiation of each of the plant organs. These phenological events are calculated from temperature functions with delays resulting from physiological stress. Stress is defined mathematically as an imbalance in the metabolite supply; demand ratio. Physiological stress is also the basis for the calculation of rates of tiller and floret abortion. Thus, tillering and head differentiation are modeled as the resulants of the two processes, morphogenesis and abortion, which may be occurring simulaneously
A meteorologically-driven yield reduction model for spring and winter wheat
A yield reduction model for spring and winter wheat was developed for large-area crop condition assessment. Reductions are expressed in percentage from a base yield and are calculated on a daily basis. The algorithm contains two integral components: a two-layer soil water budget model and a crop calendar routine. Yield reductions associated with hot, dry winds (Sukhovey) and soil moisture stress are determined. Input variables include evapotranspiration, maximum temperature and precipitation; subsequently crop-stage, available water holding percentage and stress duration are evaluated. No specific base yield is required and may be selected by the user; however, it may be generally characterized as the maximum likely to be produced commercially at a location
Cultural Practices for Seed Production from Established Stands of Western Wheatgrass
Fertilization and irrigation requirements and aftermath removal practices for maximum seed production from solid stand western wheatgrass were studied for three years near Oakley, Kansas. Conclusions from this study indicate that to obtain maximum quantity of highest quality western wheatgrass seed from established stands, the grass must be fertilized in the fall with at least 80 pounds of nitrogen per acre. Irrigation with sufficient water to fill the root zone in either the fall or early spring and again when the grass is in boot or heading is necessary. The practice of removing the aftermath following harvest by mowing and raking, coupled with successful weed control measures, may be beneficial
Irrigation and Fertilization Practices for Seed Production from Established Stands of Side-oats Grama
The objectives of this study of grass seed production were to determine the response of an established stand of a warm-season grass to irrigation and fertilizer practices with regard to the specific practices needed to produce maximum quantity of adequate quality seed per acre. Side-oats grama was chosen for the study because of the availability of adapted varieties
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Water Intake on Rangeland as Affected by Simulated Grazing Fertilization
This material was digitized as part of a cooperative project between the Society for Range Management and the University of Arizona Libraries.The Journal of Range Management archives are made available by the Society for Range Management and the University of Arizona Libraries. Contact [email protected] for further information.Migrated from OJS platform August 202
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Seed Yield and Caryopsis Weight of Side-Oats Grama
Insect control, row spacing, and nitrogen fertilization were studied. Insect control increased seed set and seed yields of side-oats grama. Seed set and seed yields per acre were higher but caryopsis weight was lower from plantings in solid stands than from spaced rows. Nitrogen fertilizer maintained seed quality and increased seed set and yields of cleaned seed. Cultural practices to obtain maximum development of caryopses, as well as large yields, should be utilized because of the great importance of seed quality in stand establishment.This material was digitized as part of a cooperative project between the Society for Range Management and the University of Arizona Libraries.The Journal of Range Management archives are made available by the Society for Range Management and the University of Arizona Libraries. Contact [email protected] for further information.Migrated from OJS platform August 202