Iddo Kan

Efforts to cope with hunger by breeding highly productive annual crops for rain-fed agriculture in stochastic-rainfall environments have had only minor success, which we attribute to biological constraints that limit the crops’ yields. We use optimization modelling to interpret experimentally measured transpiration trajectories of wild barley plants following a rain event: the plants first maximized biomass accumulation by employing their maximal transpiration rate, then switched to their minimal transpiration rate to ensure survival until maturity. Thus, breeding plants with lower minimal transpiration rates combined with higher water-use efficiency and maximal transpiration rates could increase expected yields. However, our experimental results indicate that biological constraints impose tradeoffs among maximal and minimal transpiration rates and water-use efficiency. A proposed breeding methodology identifies less biologically constrained cultivar candidates.

Managed aquifer recharge (or intentional recharge) is a purposeful human intervention designed to supplement natural enrichment processes of groundwater aquifers by various methods. It holds the potential to mitigate the impact of climate uncertainty on irrigated agriculture by restoring storage levels in depleted aquifers, the economic value of which increases during droughts. We use a high‐resolution dynamic regional hydroeconomic framework that endogenizes farming decisions in response to water quantity‐quality changes, as well as complex hydrogeological principles to analyze several institutional designs and climate scenarios applied to the Kings Groundwater Basin in California. Our analysis demonstrates that intentional recharge is of high benefit to the region, potentially increasing average groundwater levels in the region by 20% over a 20 year horizon. Additionally, we show how this practice could become the subject of second‐best arrangements among water users in the region in view of property rights to groundwater derived from recent legislation in California, thus increasing its materialization potential. However, we also find that the quantity recharged is sensitive to climate conditions and hydrological properties.

Israel’s water and vegetative agriculture sectors are interdependent, as the latter constitutes the solution for wastewater disposal. We employ a dynamic mathematical programming model that captures this interdependence for evaluating the economic damage of irrigation water salinity under two strategies of blending water sources with different salinities: field blending, which enables farmers to assign water with a specific salinity to each crop, and regional blending, under which all crops experience similar water salinity. Relative to field blending, the buildup rate of desalination under regional blending is slightly expedited; nevertheless, reallocations of water sources across sectors and crops increase the average irrigation water salinity, and the overall welfare decreases by USD 0.08 per cubic meter of irrigation water—about 20% of the water’s average value of marginal product. Salinity-sensitive crops will face the largest per hectare production reduction if regional blending replaces field blending; however, the combined variations in the prices of irrigation water and agricultural outputs may motivate farmers to move irrigation water to these crops. Under equilibrium conditions in the two sectors, a 1% increase in the average salinity of the irrigation water supplied to a region reduces the value of the marginal product of that water by 2.4% and 1.6% under field and regional blending, respectively.

We characterize the political equilibrium in a game in which the use of a natural resource is controlled by a hybrid policy that integrates a uniform price and user-specific quotas. Because lower quotas reduce the benefits of the resource users from a lowered price, and a higher price diminishes users' gains from larger quotas, the integration of the two instruments reinforces the robustness of each against lobbying for lower prices and larger quotas. We show that the resource consumption declines under a hybrid regime that follows a quotas-only regime. However, the social welfare rank of the hybrid policy versus the quotas-only and price-only counterparts is an empirical question. We use the equilibrium conditions to derive a structural discrete/continuous choice model that enables estimating resource-demand functions and two political parameters: the political influence of the controlled industry and the level of participation in the collective lobbying for reduced prices. We employ the model to irrigation-water data from Israel in the late 1980s, which was controlled by a hybrid policy, and obtain empirical support to the theoretically predicted reinforcement effect. Simulations of political equilibria under the quotas-only, price-only, and hybrid regimes indicate dominance of the latter in terms of social welfare.

Many regions worldwide have replaced quotas, as a means to controlling irrigation-water usage, with a hybrid policy that integrates private quotas and uniform prices. This paper characterizes the political equilibrium in a game in which farmers lobby for lower prices and larger quotas. We show that combining the two instruments reinforces the robustness of each against political distortion; consequently, a hybrid policy that follows a quotas-only regime reduces water usage. However, the social welfare rank of the hybrid policy versus the quotas-only and price-only counterparts is an empirical question. We use the equilibrium conditions to derive a structural discrete/continuous choice model that enables estimating the agricultural sector’s lobbying power and the level of political organization used to reduce prices. We employ the model to data from Israel during the 1980s; during that period, quotas were set at a village-specific level and prices were set at a region-specific level, thereby generating the variability required to estimate the model’s parameters. We obtain empirical support for the reinforcement hypothesis and evidence of strong political influence, but also evidence of considerable free-riding regarding price reduction. Simulations of political equilibria under the quotas-only, price-only and hybrid regimes indicate a domination of the latter in terms of social welfare.

Recent agroeconomic studies in water‐scarce countries such as Spain, Australia, Saudi Arabia, and Israel have revealed the economic viability of irrigating high‐value crops with desalinated water. However, the worldwide growth of large‐scale desalination capacities is primarily designed to resolve urban‐water scarcity, disregarding the impact of desalination on irrigation‐water salinity. We develop a dynamic hydroeconomic programming model where infrastructure capacities and allocations of water quantities and salinities in a regional water distribution network are endogenous. We show that subsidizing desalination is socially warranted because the associated reduction in irrigation‐water salinity is an external effect of water consumption by all water users. Empirical application to the entire state of Israel indicates that large‐scale desalination of seawater and treated wastewater for irrigation is optimal. This result stems from the large share of irrigation‐intensive salinity‐sensitive high‐value crops, motivated by Israel's policies to support local agriculture. Ignoring salinity results in a 45% reduction in desalinated irrigation water, a 29% reduction in farming profits, a 250% increase in water suppliers' profits, and an average deadweight loss of $1,200 a year per hectare of arable land.

Soil salinization represents a wide-spread land degradation in the world, especially in arid regions. Current management involves excessive water consumption. As a pyrolyzed residue of biomass waste, biochar has the potential to combat salinization at limited water supply, the effect and mechanism, however, remain to be clarified. We monitored the movement of salts and water in the profile of irrigation-silt soil during watering and evaporation in both laboratory and the field in Kashgar oasis in Xinjiang, China, and found that biochar exacerbates salinization within a short period of time after its application due to its high content of salts, nevertheless, it strengthens salt leaching in irrigation while intensifies salt accumulation in the top soil at the expense below during evaporation, all as results of invigorated movement of salts. Removing the top 2 cm before sowing, therefore, rejuvenates the soil well. Adsorption of biochar retards migration of salts in cation forms, but the effect is trivial. Due to increase to soil water content, biochar promotes evaporation before soil cracking. This is reversed, however, once the cracking occurs, which is inevitable in irrigated farmland and increases evaporation by 77%. Biochar counteracts soil cracking by alleviating soil compaction, lowering water evaporation by 43% at 10% of biochar application rate. Our results indicated that agriculture application of biochar creates salt distribution conducive to desalting in a mechanical way. In conjunction with the effect of anti-fracturing and enhanced salt leaching, it lowers water demand substantially, providing a new solution to the agricultural sustainability at reduced water supply.