Nitrogen fertilization effects on jojoba seed production
2001
Nelson, J.M. | Watson, J.E.
Although jojoba (Simmondsia chinensis (Link) C. Schneider) has been cultivated in the United States for many years, information is limited on the plant's nitrogen (N) requirement. A 10-year field study, which began with 2-year-old plants, evaluated the effect of N application rates on growth, flower bud survival, seed yield, seed weight, seed wax content and leaf blade total N content of three clones. Nitrogen rates were 0, 30 and 60 kg N per ha per year for the first 4 years and then were increased to 0, 60 and 120 kg N per ha per year for the remaining 6 years of the study. Nitrogen rates had a significant effect on growth in height in only 1 year. Growth was generally less in years when high seed yields were produced. Seed yields were increased linearly by N rate in 4 of the 7 years that crops were produced. Nitrogen rate had no effect on flower bud survival. Highest bud survival followed winters with temperatures no lower than -3 degrees C and little or no survival occurred when temperatures reached -6 or -7 degrees C. Seed weight was increased by N in 3 of the 7 years. A negative linear relationship existed between seed yield and seed weight. In 5 of the 7 years, seed wax content was reduced as the N rate was increased. Seed yields of clones varied among years, but AT-1310 had the highest seed wax content in 4 of the 7 years. Leaf blade total N content generally increased linearly as the N rate was increased after the first 3 years of the study. Based on leaf N content and seed yields obtained over a 7-year period, it appears that a leaf N content lower than 2% from July through September is associated with reduced seed yield in the following crop year.
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