An Irrigation and Precipitation Isotope Analysis of Crops in Central Kenya

Abstract

The water-­‐stressed environment of central Kenya is predicted to become increasingly more vulnerable with the progression of climate change. With this problem and population increases, water availability will become a source of conflict in the local communities. Understanding the water usage of plants is valuable in determining the specific strains of a crop that will produce the optimal yield in a given environment. This paper investigates the oxygen isotope (δ18O) and hydrogen isotope (δD) enrichment in maize (Zea mays) and bean (Phaseolus vulgaris) crops. Data were collected from three farms in July 2014 in the Laikipia District of Kenya that confirmed the concepts of no fractionation in soil water uptake and that differences exist between the maize and bean species. The application of different watering practices, from a combination of irrigation and precipitation, was modeled using soil moisture mass balance principles to observe their effects on plants. Results from the model indicate that differences in watering patterns are more easily observable in the oxygen isotope than the hydrogen isotope. Conditions of no irrigation, the least applied water, are more enriched than when irrigation is present and the differences in isotopic composition are only discernible to a certain level of applied water.