Recipient Organization
LOUISIANA STATE UNIVERSITY
202 HIMES HALL
BATON ROUGE,LA 70803-0100
Performing Department
Agri Economics & Agribusiness
Non Technical Summary
Irrigation water salinity is a serious problem in many parts of the tropical and subtropical world.Agriculture uses 54 percent of total groundwater extracted and 5.4 percent of the total surface water in Louisiana. According to the data from the Farm Service Agency of United States Department of Agriculture, in 2014 of all the crop acres planted, 55.4% of the area overlying the Mississippi River Alluvial Aquifer (MRAA) was irrigated. Thus, the lack of quality groundwater and surface watercould severely impact the agriculture-based economy. The continuous increase in salinity is likely to have a significant impact on Louisiana agriculture. The parishes above MRAA and Chicot aquifer are the most productive row crop areas in Louisiana and the regions use a significant amount of groundwater for crop irrigation. It is important to understand the impact of potential cropping pattern shifts in this region. Water allocation extends beyond the state line as these aquifers are shared with other states (Mississippi in case of MRAA and Texas in case of Chicot aquifer). Understanding transboundary water management issues would be important for the long-term sustainability of these aquifers, as well as for the long-term productivity and viability of agriculture in Louisiana.We will use a dynamic model to understand the relationship between irrigation water salinity and crop yield loss in Louisiana. To assess the impact of salinity on land value loss, we will use a hedonic method. To understand the broader impact of salinity on the economy, we will use an input-output model. To understand the groundwatersharing between two states and to consider the endogenous and exogenous risk, we will develop dynamic optimization models. The ultimate goal of the project is to support a profitable farming system that also protects groundwater resources.
Animal Health Component
70%
Research Effort Categories
Basic
20%
Applied
70%
Developmental
10%
Goals / Objectives
Calculate the dynamics of salt deposits in soil from saline irrigation water application andIdentify the yield and economic loss,Determine land value impact using a spatial hedonic regression modelCalculate the economic impacts of an alternative solution for the salinity problem underThe adoption of more salt-tolerant crop varietiesThe change in cropping system to incorporate more salt tolerant cropsDevelop models for water extraction behavior under endogenous and exogenous risksDevelop models for transboundary allocation of groundwater under salinity risk
Project Methods
Objective 1: Calculate the dynamics of salt deposits in soil from saline irrigation water application and i. identify the yield and economic loss, ii. Land value impact using a spatial hedonic regression modelGenerally speaking, both MRAA and Chicot aquifers are showing an upward trend in salinity. A dynamic optimization model will be developed that maximizes farm income given the dynamics of water and soil salinity in the region.The yield function will be a switching function with two different slopes based on whether the salinity level is below or above the threshold point. The dynamic relationship between irrigation water and soil salinity will be explored. The dynamic model will consider soil salinity buildup and yield loss due to saline groundwater use in the study region. The model will help to calculate the variations in soil salinity buildup due to the difference in crop grown, soil type, and soil layer. It will also help to understand how long it will take to realize different levels of soil salinity in the study region.We also want to establish the relationship between the land value (or land rental value) and groundwater well depth and water salinity level. For the purpose, we will use a spatial hedonic regression model. The spatial regression model will use land value or land rental value as a dependent variable and salinity, well depth variable as explanatory variables.Data sources for this objective include our recently conducted survey data (survey conducted in 2015, and 2016) collected from Louisiana crop producers. A GIS map will be developed for the study area with soil and crop information. This map will be provided to parish agents and land credit bank in the study region to obtain a land rental rate.Objective 2: Calculate the economic impacts of alternative solution for salinity problem Increased water salinity and soil salinity reduce crop yield (see Figure 4). According to FAO & Panta et al. (2014), this yield reduction depends on salt concentration in water. If the concentration of salt in water is 7.7, 2.5, 7.2, 9.4, and 5.5 desi Siemen dS/m, respectively, the yields in sorghum, corn, wheat, cotton, and soybeans are reduced by 10% with afurther increase in salt concentration in irrigation water by 9.6, 5.5, 12.6, 16.8, and 7.2 dS/m, the yield loss will be 50%.Task 1. Based on the modeling approach developed for the objective 1, we will identify the expected time when water applied or soil used would get salinity levels that would result in significant yield reductions. We will model the economic impacts of this salt concentration increase and its impacts on yields and overall crop profitability to both the agricultural economy and the entire Louisiana economy using input-output modeling. IMPLAN software (http://www.implan.com/) will be used to estimate the economic impact model. IMPLAN is an input-output based model that contains detail information for each county for the entire U.S. We will use a predictive value of crop yield decrease or crop mix changes due to salinity and input that information in IMPLAN. The dynamic model developed in method 1 (for objective 1) provides the change in yield information due to increase in water and soil salinity. Multipliers are generated in IMPLAN that evaluate the response of a region's economy at a different scale to an impact from salinity. Economic activities generated include direct, indirect, and induced impact on employment, wages and total values of output.Task 2: The economic impact of salinity in irrigation water combined with soil salinity build-up could be substantial. There are several ways to overcome this problem. We will look into following options:We will identify the role of salinity resistant variety of soybeans and other major feed grain crops. Although research in soybean has indicated gmSALT3 gene is capable of withstanding salt tolerance and Tiefeng 8 is identified as one such variety for the purpose, there will be yield reduction of a certain amount. Similarly, we will analyze the economic feasibility of introducing HKT1;5-like gene containing wheat as the possibility of substitute crop to the existing wheat crop. Results had shown that a wheat variety with this gene is capable of increasing 25% grain yield under saline field conditions. The International Rice Research Institute has developed several salinity resistant varieties (IRRI-12, IRRI-13, IRRI-24, IRRI-25, IRRI-26, IRRI-28), although those are not common in Louisiana. We will identify the economic impact of using alternative salinity tolerant species.Instead of the current cropping system prevalent in the region, we will look into the economic effects of incorporating more salt tolerant crops such as cotton, wheat, barley, and sorghum. Another alternative is to leave land fallow. The possibilities of utilization of halophytic plant species as agricultural crops are very limited although some exceptions, e.g. Chenopodium quinoa from Chenopodiaceae family or wild relatives of cultivated Triticeae such as tall wheatgrass (Thinopyrum elongatum) do exist.We will limit the changes to only crops currently prevalent in the region (replacing soybeans by say cotton or changing cropping system to a wheat-based system). We will identify the economic impacts of this cropping system change and fallowing by calculating the direct, indirect, and induced effects on the affected parish, region and state economies.Objective 3: Modeling Endogenous and Exogenous RiskWe use the framework employed by Polasky et al. (2011). In this framework, a planner is solving an infinite horizon profit maximization problem and has to decide the amount of groundwater withdrawal in each period. We will derive theoretical and empirical solutions for this equation when there is only endogenous risk, only exogenous risk, and when there are both endogenous and exogenous risks present at the same time. We will compare these results to previous literature and show the implications of alternative risk considerations in groundwater extraction behavior by farmers in the study region.Objective 4: Transboundary water allocationWe provide several scenarios that are possible in the dynamic version of the groundwater management problem associated with the transboundary aquifers (MRAA and Chicot).Scenario I. Dynamic analog of the static model with recharge rate and sole ownershipScenario II. Optimal social plan with two statesThis situation results if two states extract groundwater from a shared aquifer independently. We will expand this formulation when there are strategic behaviors involved in water extraction by two states. We will calculate several equilibria solutions (analytical, numerical or approximate solutions depending on the problem formulations) in differential games (open loop Nash, feedback Nash, open-loop Stackelberg and feedback Stackelberg solutions) settings (Dockner, 2000). We will also calculate i) welfare under these strategies, ii) compare these outcomes with an optimal solution, and iii) suggest policies to make these solutions optimal. These models and solutions will also be derived when there are multiple sectors and multiple players in both states. Mathematica and Python software will be used to obtain the solutions under these scenarios.