Author
|
Submitted to: Dahlia Greidinger International Symposium
Publication Type: Abstract Only Publication Acceptance Date: 2/29/2016 Publication Date: N/A Citation: N/A Interpretive Summary: Technical Abstract: Arid regions face increasing scarcity of fresh water, increasing salinization of water and soil resources and often increasing demand to minimize nutrient loading to drainage waters. Understanding the interaction of abiotic stress on crop production is essential for management and optimization of resources as well as economic crop production. We discuss plant response to interactive effects of combinations of salinity, drought, nitrogen and boron stress. Often plant response studies and subsequent recommendations regarding water requirements and drought stress, salinity stress and management, boron toxicity and nutrient requirements are provided from single stress experiments. Under field conditions there are often multiple stresses occurring simultaneously. The simplest model, adding the individual responses to abiotic stress to predict yield, has been discredited, but there are conflicting reports regarding how multiple abiotic stresses interact. Many models consider an interactive effect that is multiplicative of the response to stresses, in contrast some recommendations are to consider only the most severe stress when managing for yield loss. Many literature reports on salinity and nitrogen conclude that increased fertilization increases yield under saline conditions. However most of these reports consider only two treatments; saline with current nutrient practices and saline with added nutrients. Unless these studies have established the minimal requirements under non-stress conditions the conclusions are not justified and are only useful for current management at that specific site. Studies with either multiple salinity and nutrient levels or measurement of nutrient status in the plant and soil, generally reach an opposite conclusion: Nitrogen requirements are best considered as proportional (scaled) to the relative yield. Thus with expected yield loss due to salinity, less N is generally required than under non-stressed conditions. There is information that Cl salts can reduce nitrate uptake but as will be explained under field conditions this is of lessor consideration than the reduced N demand caused by salinity. Examples from various studies are provided. Although there are some crops that demonstrate decreased K uptake under saline conditions it is not clear that increased K application can be recommended for saline environments, and in fact in many regions increased soil salinity is also associated with increased soluble K. P nutrition and salinity interaction has been reported but as will be discussed, is more related to solution composition (Ca, and pH or alkalinity) than osmotic stress. There are many studies with the objective of evaluating the effects of water and salinity stress, most are difficult to evaluate because they generally consist of irrigation with waters of varying salinity, superimposed on different fixed applications of water. Reduced transpiration of salt stressed plants results in higher water content and less water (matric potential) stress than non saline treatments with the same water application. Comparison of response to water stress under saline and non-saline conditions requires direct measurement of soil water content or matric potential. Estimation of water consumption based on reduction in biomass production is not adequate as it assumes that water use efficiency is constant under salt stress- an assumption that has been found to not be valid for many crops. Further, the response to these potentials (osmotic and matric) does not appear to be equal. What are needed are experiments evaluating response to multiple abiotic stresses. These studies are difficult due to experimental constraints, but there are a few that consider three stresses simultaneously. At present with insufficient information, the multiplicative response models provide the best estimate of the effect of these com |
