Review of measured crop water productivity values for irrigated wheat, rice, cotton and maize

Irrigation management under water scarcity

Irrigated agriculture is a vital component of total agriculture and supplies many of the fruits, vegetables, and cereal foods consumed by humans; the grains fed to animals that are used as human food; and the feed to sustain animals for work in many parts of the world. Irrigation worldwide was practiced on about 263 Mha in 1996, and about 49% of the world's irrigation occurred in India, China, and the USA. The objectives of this paper are to (i) review irrigation worldwide in its ability to meet our growing needs for food production, (ii) review irrigation trends in the USA, (iii) discuss various concepts that define water use efficiency (WUE) in irrigated agriculture from both engineering and agronomic viewpoints, and (iv) discuss the impacts of enhanced WUE on water conservation. Scarcely one-third of our rainfall, surface water, or ground water is used to produce plants that are useful to mankind. Without appropriate management, irrigated agriculture can be detrimental to the environment and endanger sustainability. Irrigated agriculture is facing growing competition for low-cost, high-quality water. In irrigated agriculture, WUE is broader in scope than most agronomic applications and must be considered on a watershed, basin, irrigation district, or catchment scale. The main pathways for enhancing WUE in irrigated agriculture are to increase the output per unit of water (engineering and agronomic management aspects), reduce losses of water to unusable sinks, reduce water degradation (environmental aspects), and reallocate water to higher priority uses (societal aspects).

Enhancing Water Use Efficiency in Irrigated Agriculture

Effect of water stress at different development stages on vegetative and reproductive growth of corn

with the Agricultural Research Service (ARS) and various government agencies and private institutions have provided a great deal of fundamental information relating spectral reflectance and thermal emittance properties of soils and crops to their agronomic and biophysical characteristics. This knowledge has facilitated the development and use of various remote sensing methods for non-destructive monitor- ing of plant growth and development and for the detection of many environmental stresses which limit plant productivity. Coupled with rapid advances in computing and position- locating technologies, remote sensing from ground-, air-, and space-based platforms is now capable of providing detailed spatial and temporal information on plant response to their local environment that is needed for site specific agricultural management approaches. This manuscript, which empha- sizes contributions by ARS researchers, reviews the biophysi- cal basis of remote sensing; examines approaches that have been developed, refined, and tested for management of water, nutrients, and pests in agricultural crops; and as- sesses the role of remote sensing in yield prediction. It con- cludes with a discussion of challenges facing remote sens- ing in the future.

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Remote Sensing for Crop Management

Effect of drip irrigation regimes on yield and quality of field grown bell pepper

This study was designed to evaluate the crop water stress index (CWSI) for low-energy precision application (LEPA) irrigated corn (Zea mays L.) grown on slowly-permeable Pullman clay loam soil (fine, mixed, Torrertic Paleustoll) during the 1992 growing season at Bushland, Tex. The effects of six different irrigation levels (100%, 80%, 60%, 40%, 20%, and 0% replenishment of soil water depleted from the 1.5-m soil profile depth) on corn yields and the resulting CWSI were investigated. Irrigations were applied in 25 mm increments to maintain the soil water in the 100% treatment within 60–80% of the “plant extractable soil water” using LEPA technology, which wets alternate furrows only. The 1992 growing season was slightly wetter than normal. Thus, irrigation water use was less than normal, but the corn dry matter and grain yield were still significantly increased by irrigation. The yield, water use, and water use efficiency of fully irrigated corn were 1.246 kg/m2, 786 mm, and 1.34 kg/m3, respectively. CWSI was calculated from measurements of infrared canopy temperatures, ambient air temperatures, and vapor pressure deficit values for the six irrigation levels. A “non-water-stressed baseline” equation for corn was developed using the diurnal infrared canopy temperature measurements as Tc–Ta = 1.06–2.56 VPD, where Tc was the canopy temperature (°C), Ta was the air temperature (°C) and VPD was the vapor pressure deficit (kPa). Trends in CWSI values were consistent with the soil water contents induced by the deficit irrigations. Both the dry matter and grain yields decreased with increased soil water deficit. Minimal yield reductions were observed at a threshold CWSI value of 0.33 or less for corn. The CWSI was useful for evaluating crop water stress in corn and should be a valuable tool to assist irrigation decision making together with soil water measurements and/or evapotranspiration models.

Evaluation of crop water stress index for LEPA irrigated corn

Center-pivot sprinklers are rapidly expanding on the Southern High Plains, and LEPA (low energy precision application) application methods are widely used in this region to reduce water application losses, to use the relatively low well yields, and to reduce energy requirements for pressurization This study was conducted to evaluate LEPA irrigation response of corn (Zea mays L) on slowly permeable Pullman clay loam (fine, mixed, thermic Torrertic Paleustoll) The effects of irrigation amount were investigated in a field study during the 1992 and 1993 cropping seasons at Bushland, Texas In 1992, a wetter than normal season, grain yields varied from 06 to 12 kg/m2 while in 1993, which was a season with slightly less than normal rain, grain yields varied from 04 to over 15 kg/m2 as irrigations increased from no-post plant irrigations to fully meeting the crop water use Irrigation amounts for the full irrigation varied from only 279 mm for the wet year to over 640 mm for the more normal year A significant relationship was found between grain yield and water use for the two years described as GY (kg/m2) = 000169 [WU (mm) – 147] with an r2 of 0882 and a Sy/x of 010 kg/m2 Deficit irrigation of corn, even with LEPA, reduced yields by affecting both seed mass and kernels per ear Generally, the grain yield was in proportion to dry matter yield LEPA irrigation was shown to be efficient in terms of partitioning the applied water into crop water use Irrigation amounts should not exceed 25 mm for alternate furrows (076-m rows) LEPA on the Pullman-type soils with furrow dike basins

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Attila Yazar

Papers

Effect of drip irrigation regimes on yield and quality of field grown bell pepper

Evaluation of crop water stress index for LEPA irrigated corn

Yield and Water Use Efficiency of Corn in Response to LEPA Irrigation

LEPA and trickle irrigation of cotton in the Southeast Anatolia Project (GAP) area in Turkey

Optimum lateral spacing for drip-irrigated corn in the Mediterranean Region of Turkey