Determining pomegranate water and nitrogen requirements with drip irrigation

Abstract

Despite being an ancient crop there is limited knowledge on the water and nitrogen (N) requirements of pomegranate. We conducted research at the University of California, Kearney Agricultural Research and Extension Center (KARE) to determine the water and N requirements of a developing pomegranate orchard. Pomegranate trees (Punica granatum L. var. Wonderful) were planted in 2010. The irrigation treatments were surface drip irrigation (DI) and subsurface drip irrigation (SDI) with three N sub-treatments (N application rates of 50, 100, and 150 % of current practice) and 5 replications in split-plot design. A weighing lysimeter located in the experimental field was used to automatically irrigate the orchard after 1.0 mm of measured crop water use. The trees received uniform application of fertilizers and water during the first two years of growth to insure uniform stand establishment prior to beginning the experiment. The pH of the irrigation water was maintained at 6.5+/-0.5 by injection of N as urea sulfuric acid (US-10; 10% N). Differential N treatments were started in 2012 and continued through the end of the project. Phosphorus (PO 4-P) was continuously injected during irrigation and potassium (K 2 T) was injected weekly. We report the results of the study from 2013 to 2015. From 2013 to 2015 the applied N ranged from 62 to 332 kg/ha and the total yields ranged from 33,144 to 57,769 kg/ha. There were no statistical differences in yield within any year related to total applied N. The yearly applied irrigation water increased as the plant size increased. The total water requirement is approximately 952 mm and the maximum daily water use was 10.5 mm. The DI irrigation application went from 645 mm to 932 mm and the SDI application increased from 584 mm to

Subsurface Drip Irrigation Reduced Nitrous Oxide Emissions in a Pomegranate Orchard

“…The field treatments included two main irrigation treatments as surface drip irrigation (DI) and subsurface drip irrigation (SDI) and three N application rates as sub-treatments. The findings on treatment effects on yield, N requirement, and weed as well as C and N dynamics from this field research are reported in Ayars et al [17] and Tirado-Corbalá et al [18], respectively. Conclusions included that although yields were not significantly different between the two irrigation systems, SDI used less water with much lower weed pressure than DI.…”

“…Wang et al [21] reported that increased soil moisture stimulated the growth of ammonia-oxidizing bacteria and nitrite reducer (nirK) and total N 2 O emissions were positively correlated to ammonia-oxidizing bacteria abundance. The SDI also resulted in higher water use efficiency and much lower weed pressure Ayars et al [17] as well as higher N use efficiency Tirado-Corbalá et al [18]. All the benefits plus the reduced N 2 O emissions in this study make SDI preferable to the DI.…”

“…However, Tirado-Corbalá et al [18] also showed that the SDI soil at N1 and N2 levels did not result in elevated TN and NO 3 concentrations at 105-120 cm soil depth suggesting reduced leaching risk using the high frequency irrigation. Both Ayars et al [17] and Tirado-Corbalá et al [18] have demonstrated that N3 treatment provided unnecessarily high N for the pomegranate demand. Overall, the lower soil N 2 O concentration in SDI plots than that from DI may also be due to more efficient plant uptake.…”

“…Wonderful) and continued for five years. Detailed information about the field set up can be found in Ayars et al [17]. Briefly, the field experiment included two main irrigation treatments: DI and SDI, and three sub-treatments N application rates of 50, 100, and 150% of current practice for a total six treatments in five replications (blocks) in a split-plot design.…”

“…For the additional N requirement, ammonium nitrate (20% N or AN20) was injected to N2 and N3 treatments. For P and K supply, phosphoric acid (H 3 PO 4 ) and potassium thiosulfate (25% K from K 2 O and 17.5% S) were injected to all treatments at irrigation water concentrations of 15-20 mg L -1 for P and 50 mg L -1 for K (refer to Ayars et al [17] for details). Fertilizer application began in late April or early May through August for both 2012 and 2013.…”