Soil Texture, Nitrogen and Irrigation Water Quality Influence on Pecan Kernel.

Pecans are one of the highest sources per capita income but also have high water demand. Since surface water is becoming a limited resource and groundwater has been used as a supplementary source of water in the southwestern arid lands of the United States. This research was done in pecan farms along the Rio Grande, from Derry NM to Fabens TX. The objectives of the research were to evaluate the effects of soil texture variation and soil and groundwater salinity on full pecan kernel and length. The other objectives were to assess the variability of soil nitrogen among the experimental orchards, and investigate the effects of diurnal temperatures variation during winter and spring on pecan trees bud break. One temperature sensor was installed at each location and air temperature was recorded every ten min. Soil samples were taken every four months during a two-year period from six depths (0-20, 20-40, 40-60, 60-80, 80-100 and 100-120 cm). Well water samples were also collected once every four months for two years. All of them were analyzed for soil texture, sodium absorption rate (SAR), pH, electrical conductivity (EC), nitrate-N and ammonium (NH₄). Pecan nut samples were collected for two consecutive years and kernel percentage in a 300 g sample and Zn, P, Mg, Ca, Al, Na, K, and Fe contents were determined. Bud braek was earlier in orchards with higher number of heating hours during Feb. and March. The statistical analysis showed a significant inverse relationship between clay content and kernel size. Increasing soil (or irrigation water) salinity also decreased kernel size. Pecan trees that are planted in clayey soils produced smaller nuts compared to those grown in sandy soils. Pecan length was smaller in orchards irrigated with brackish groundwater and kernel quality decreased eith increasing soil and irrigation water salinity. Overall, continuous irrigation with brackish groundwater will be dterimental for pecan production in the study area.