In the states of Texas and Oklahoma, it is estimated that pecans contribute more than $90 million and $14 million to each state’s economy, respectively (Noble Research Institute, 2010). A growing interest in pecans stems from explosive growth in the export market for pecan nuts during the past several decades (Lillywhite et al., 2014). Irrigation has been found to be crucial in the establishment and growth of young nut-bearing trees in areas such as Alabama (Patterson et al., 1990) and Georgia (Wells, 2017), but little is known about the relationship between irrigation and establishment in the southern Great Plains. In pecans, a recent study by Wells (2017) aimed to determine the appropriate irrigation rates and effects on growth of young pecan trees in Georgia. Wells compared two microsprinkler systems with emitters of different pressures and a nonirrigated control. During the first 2 years of the experiment, irrigated trees had greater trunk diameter growth than the nonirrigated control trees. This work agrees loosely with previous work in Alabama by Patterson et al. (1990), who compared a nonirrigated control with a drip irrigation system with five emitters per tree. No difference in trunk diameter was found during the first year between irrigated and nonirrigated trees. However, in subsequent years, Patterson et al. (1990) did find that irrigated trees had significantly larger trunk diameters.
Although some research exists on irrigation effect on the growth of young pecan trees, little to none exists on the effects of irrigation delivery system on nutrient uptake in pecan trees. Neilsen et al. (1995) investigated the effects of emitter (jet or microsprinkler) and frequency of irrigation and their effects upon ‘Gala’ apples (Malus ×domestica). In their study, leaf concentrations of potassium (K), magnesium (Mg), copper (Cu), and manganese (Mn) were affected significantly by irrigation type and frequency. However, fertigation of nitrogen (N) and phosphorus (P) occurred, potentially leaching the soil of some nutrients and consequently leading to different element leaf concentrations.
Effects of differing irrigation levels on individual pecan nut weight has been investigated previously. Garrot et al. (1993) designed four irrigation treatments based on a crop water stress index resulting in a wet, medium, and dry treatment as well as a grower-designated irrigation treatment. Sixteen trees established in 1967 were included in the 4-year experiment that started in 1988. Data pooled over the 4 years showed a decrease in pecan nut weight in relation to a decrease in water. However, the number of saleable kernels was unaffected. Although the relationship between amount of water and nut quality might be documented, there is a lack of research concerning the effects of the irrigation water delivery system and its effects upon the nut quality of young pecan trees.
Research is needed to determine the effects of irrigation water delivery method on growth, nut quality, and nutrient absorption of young pecan trees. The objectives of our study were to determine the effects of different types of drip and sprinkler irrigation systems, and the periodicity of irrigation as well as a nonirrigated control on the change in trunk diameter, kernel percentage, pecan nut weight, and leaf element concentrations.
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