, 55 % lower compared to CF30, while no differences in nitrous oxide emissions were observed between treatments (p > 0.05). No yield differences between irrigation systems were observed in two of the rice seasons (p > 0.05) while AWDI promoted yield reduction in one of the seasons (p < 0.05). When rice yield and greenhouse gases (GHG) emissions were considered together, the AWDI irrigation system allowed for lower yield-scaled total global warming potential (GWP). Higher irrigation water productivity was achieved under AWDI in two of the three rice seasons. These findings suggest that AWDI could be an option for reducing GHG emissions and increasing irrigation water productivity. However, AWDI may compromise grain yield in certain years, reflecting the importance of the need for fine tuning of this irrigation strategy and an assessment of the overall tradeoff between relationships in order to promote its adoption by farmers.

No abstract

Recent Colorado, USA water law provisions allow a portion of irrigation water to be leased between agricultural and other users. Reducing consumptive use (CU) through deficit irrigation while maintaining some crop production could allow farmers to earn revenue from leasing water rights. This observational study aimed to determine if deficit irrigation of alfalfa (Medicago sativa L.) can be used to reduce CU, provide parameters for an alfalfa crop water production function (WPF), and evaluate the potential for improved farm income by leasing water. Soil water balance, evapotranspiration (ET), and dry matter yield from eight commercial fields (1.70 to 2.14 ha zones), growing subsurface drip-irrigated alfalfa, were monitored for five seasons (2018–2022) at Kersey, Colorado. Four irrigation treatments [Standard Irrigation (SI) = irrigate when soil water deficit (D) exceeds management allowed depletion (MAD); Moderate Deficit Irrigation (MDI) = 70% of SI; Severe Deficit Irrigation (SDI) = 50% of SI; and Over Irrigation (OI) = 120% of SI] were applied, with two zones per treatment. Reductions in CU ranged from 205 to 260 mm per season. The shape of the alfalfa WPF (dry biomass yield vs. ET) was concave, indicating that water use efficiency (WUE) could be optimized through deficit irrigation. The average WUE was 0.17 Mg ha−1 cm−1 and tended to increase with greater deficits. Deficit irrigation also increased the relative feed value. If conserved CU from deficit irrigation can be leased into a transfer water market, farmers could profit when the water lease revenue exceeds the forgone profit from alfalfa production. We found incremental profit from deficit irrigation and water leasing to be positive, assuming 2020 prices for hay ($230 bale−1) and water prices above $0.50 m−3.

No abstract

Crop production in Uruguay has changed significantly in recent years, not only in terms of expansion of cultivated area but in its main features. These changes came along with significant increase in land prices and agricultural inputs causing intensification on land use. In order to get high profits the traditional crop-pasture rotations should be strongly oriented to a continuous cropping system and strengthened on grain crops. The potential of agricultural systems is highly dependent on rainfall, therefore, the adoption of irrigation represents an attractive alternative to increase productivity and reduce vulnerability of productive systems. Maize performance and its C4 metabolism enhancing water use efficiency represent an excellent choice for farmers. Nitrogen (N) is one of the main nutrients affecting plant growth and maize grain yield response to N application is well known. In order to reduce N losses, increase uptakes and improve N use efficiency, optimum amount of water and N should be applied. The objective of this study was to assess the interaction between irrigation and N application rates and its effect upon yield. A three year field experiment was carried out in Colonia, Uruguay (34º25´S, 58º0´W), at the Experimental Station of the National Agricultural Research Institute (INIA) "La Estanzuela", in three growing seasons (2011-2014), under a Vertic Argiudoll soil. The experimental treatments consisted in eight urea treatments with four levels of N application (0, 50, 100, 150 and 200 KgN/ha) at three different phenological moments (V6, V10 and V14) under rainfed and supplementary irrigated conditions. The study showed that the average grain yield on irrigated conditions was 12.060 ± 2282 kg/ha for all treatments and 7.089 ± 1615 kg/ha under rainfed conditions. Results indicated that due to the strategies of N application and irrigation water application, yields increased as N rate application increased. Furthermore, results showed that under rainfed conditions N treatments did not translated in significantly increased grain yields, indicating that when water is scarce, the effect of nutrients are scattered, and the achievable grain yields are not reached. The maximum grain yield was obtained for 200 kgN/ha application treatments, showing an increase of 5.337 kg/ha under irrigated conditions, while on rainfed conditions was only 1.500 kg/ha. However, in order to avoid N losses and improve N use efficiency, the amount of N fertilizer should not be applied at one time. It can be concluded that supplementary irrigation is a fundamental technology not only to maximize and stabilize grain yields but to enhance N use efficiency.