Submitted to: Industrial Crops and Products
Publication Type: Peer reviewed journal
Publication Acceptance Date: 6/13/2014
Publication Date: 7/1/2014
Citation: Jiangang, L., Bronson, K.F., Thorp, K.R., Mon, J., Mohammad, B., Mccloskey, W., Ray, D.T., Qingquan, C., Guangyao, W. 2014. Lesquerella seed and oil yield response to split-applied N fertilizer. Industrial Crops and Products. 60:273-279. Interpretive Summary: Agronomic management guidelines and recommendations are sorely lacking for new oilseed and biofuel crops such as lesquerella. We conducted a two-year field trial to study the response and of Nitrogen (N) fertilizer rates under well-watered and water-stressed conditions in Arizona. Despite low initial soil nitrate, pre-plant N fertilizer did not affect early lesquerella growth. With higher N fertilizer rates, seed and straw N concentration increased in both well-watered and water-stressed plots. Seed and oil yields showed a quadratic (i.e. diminishing curve) response to N fertilizer rate. Optimum N fertilizer rate for oil yield was lower than the N fertilizer rate for the optimum seed yield. Well-watered lesquerella had a greater optimal N fertilizer rate for oil yield 240 kg N ha-1) than did water-stressed lesquerella in the second season (180 kg N ha-1). The results of this study provide practical guidelines for N fertilizer management for lesquerella in the southwestern US.
Technical Abstract: Agronomic management information is critical for successfully commercial production of new crops such as lesquerella [lesquerella ferndleri Gray (Wats.)]. Response of lesquerella to six nitrogen (N) fertilizer rates under well-watered and water-stressed treatments were studied in irrigated desert conditions in southwestern of United States to establish guidelines for lesquerella N management. Seed and oil yield, seed and straw N concentrations, N harvest index, and total N uptake were recorded at harvest and plant samples were also taken during growing season for plant N status. Although soil NO3-N was low due to a cover crop to remove excessive N in the soil, pre-plant N fertilizer did not affect lesquerella growth at early growth stage. For the treatments with high N fertilizer rates (224 and 336 kg ha-1), lesquerella plant N concentrations were relatively stable before the first bloom, decreased drastically until mid-bloom (one month after the first bloom), and then continued to decrease at a lower rate until harvest. As N fertilizer rates increased, seed and straw N concentration increased linearly under both well-watered and water-stressed conditions. Lesquerella seed and oil yield had a quadratic relationship with N fertilizer rate. Because seed oil concentration decreased as N fertilizer increased, N fertilizer rate for the optimum oil yield was lower than the N fertilizer rate for the optimum seed yield. According to seed and oil yield as well as plant N status under different N fertilizer rates, we provided a guideline for N fertilizer management for lesquerella crop.