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In California, alfalfa is grown on a large area ranging between 325,000 and 410,000 hectares and ranks among the thirstiest crops. While the hay production industry is often scrutinized for the large usage of the state's agricultural water, alfalfa is a crucial feed-supplier for the livestock and dairy sectors, which rank among the most profitable commodity groups in the state. Sub-surface drip irrigation (SDI), although only practiced on approximately 2% of the alfalfa production area in California, is claimed to have the potential to significantly increase hay yield (HY) and water productivity (WP) compared with surface irrigation (SI). In 2014-2016 we interviewed a number of growers pioneering SDI for alfalfa production in Central and Southern California who reported that yield improvements in the order of 10-30% and water saving of about 20-30% are achievable in SDI-irrigated fields compared with SI, according to their records and perceptions collected over few years of experience. Results from our research on SDI at the University of California, Davis, revealed significantly smaller yield gain (~5%) and a slight increase of water use (~2-3%) that are similar to findings from earlier research studies. We found that most of the interviewed alfalfa producers are generally satisfied with their SDI systems, yet face some challenges that call for additional research and educational efforts. Key limitations of SDI include high investment costs, use of energy to pressurize water, the need for more advanced irrigation management skills, and better understanding of soil-water dynamics by farm personnel. SDI-irrigated fields also need accurate water monitoring and control, attentive prevention and repair of rodent damages, and careful salinity management in the root zone. In this paper we attempt to evaluate the viability of the SDI technology for alfalfa production on the basis of preliminary results of our research and extension activities, with focus on its water and energy footprints within the context of resource efficiency. [ABSTRACT FROM AUTHOR]

Innovative irrigation practices can enhance water efficiency, gaining an economic advantage while also reducing environmental burdens. In some cases the necessary knowledge has been provided by extension services, helping farmers to adapt and implement viable solutions, thus gaining more benefits from irrigation technology. Often investment in technological improvements has incurred higher water prices, however, without gaining the full potential benefits through water efficiency. Farmers generally lack adequate means and incentives to know crops’ water use, actual irrigation applications, crops’ yield response to different water management practices, and thus current on-farm water-efficiency levels. Those general difficulties are illustrated by our two case studies investigating options, stimuli and difficulties to improve water-efficient practices. The two areas have strong stimuli for improvement but lack a knowledge-exchange system to help farmers and resource managers identify scope for improvements. Partly for this reason, farmers’ responsibility for efficient water management has been displaced to hypothetical prospects, e.g. extra supplies from reuse of treated wastewater or a long-term low water pricing. In both cases a displaced responsibility complements the default assumption that farmers’ irrigation practices already have adequate water-use efficiency. Under current circumstances, agricultural water management will maintain the unknown water-efficiency level and farmers will have weaker incentives to make efforts for more efficient practices. A continuous knowledge-exchange is necessary so that all relevant stakeholders can share greater responsibility across the entire water-supply chain. On this basis, more water-efficient management could combine wider environmental benefits with economic advantage for farmers. [ABSTRACT FROM AUTHOR]

A methodology to assess performance of pressurized irrigation distribution networks is presented, which is based on generation of flow configurations from simulated delivery scenarios, and on subsequent analysis of network operation and delivery achievements. The rationale of the methodology entails simulating the peak-demand flow configurations in the pipe network through a deterministic-stochastic combined agro-hydrological model, and forecasting the delivery performance by means of a hydraulic simulation model and of some specific performance indicators. The agro-hydrological model generates disaggregated information on soil water deficits for all the cropped fields downstream from the delivery hydrants, and forecasts the demand flow hydrographs and irrigation deliveries for the entire service area during peak-demand periods. The simulated-demand flow configurations are then passed on to the hydraulic simulation model, which evaluates the hydraulic performance achievable by the pipe network. The performance analysis is then refined using additional indicators specifically adapted to pressurized irrigation networks. The proposed methodology was applied to a large-scale pressurized irrigation system of southern Italy that is in need of modernization. Results proved the usefulness of the combined use of simulation tools as components of an analytical framework to address modernization and re-engineering of existing irrigation delivery networks, on the basis of targeted delivery performance. [ABSTRACT FROM AUTHOR]

This study was conducted on an irrigated area of southern Italy to analyze the current operation of a large-scale irrigation delivery system and the effects of the operation procedures on crop irrigation management and aquifer salinity increase. The area is characterized by relatively high levels of groundwater salinity in the summer that are probably due to intensive groundwater pumping by farmers during periods of peak irrigation demand, with the resulting seawater intrusion. Two alternative delivery schedules, namely the rotation delivery schedule and the flexible delivery schedule, referred to as RDS and FDS, respectively, were simulated using a soil-water balance model under different combinations of crop, soil and climatic conditions. The first set of simulations concerned the farm irrigation management constrained by the rotational delivery used by the local water management organization. The second scenario simulated the farm irrigation schedule most commonly used by growers in the area for maximizing crop yields. Based on crop irrigation management under RDS and FDS, two alternative operational scenarios were also developed at the scheme level and then compared for evaluation. Winter and summer salinity maps of the aquifer were developed by interpolating salinity measurements of the groundwater samples collected during the 2006 irrigation season. From these maps, a close relationship can be inferred among delivery schedule, aquifer exploitation and salinity increase, which justifies the need for implementing FDS that might reduce the groundwater demand for irrigation. [ABSTRACT FROM AUTHOR]