Carbon and Nitrogen Dynamics Affected by Drip Irrigation Methods and Fertilization Practices in a Pomegranate Orchard

Abstract

Knowledge of carbon (C) and nitrogen (N) dynamics under different irrigation practices in pomegranate orchards is novel and essential to develop sustainable production systems. The aim of this research was to determine the effect of high-frequency drip irrigation and different rates of N fertilizer on C and N distribution in the soil and N uptake by pomegranate fruit and leaves. The main treatments were surface drip irrigation (DI) and subsurface drip irrigation (SDI), and the sub-treatments used were three initial N rates (N1, N2, and N3). As trees grew larger, the N application rate increased. From 2013-2015, trees received the following rates of N: 62-113 (N1), 166-263 (N2), or 244-342 kg/ha (N3). Soil and leaf total C (TC) and N (TN), soil dissolved organic C (DOC), soil nitrate (NO 3 − ), and total N uptake by fruit were evaluated between 2012 and 2015. Soil samples were collected to 120 cm depth at 15 cm increments. DI resulted in higher concentrations of TN, TC, NO 3 − , and DOC in the upper 75 cm depth than SDI. The N3 treatment resulted in higher concentrations of TN, TC, NO 3 − , and DOC under both DI and SDI. Neither DI nor SDI at the N1 or N2 levels increased TN and NO 3 − concentrations at 105-120 cm soil depth, indicating reduced leaching risk using high-frequency drip irrigation. Higher N uptake by fruit was observed in SDI than in DI in 2014 and 2015, and in N2 and N3 treatments compared with N1 in 2013 and 2014. The data indicate that the application rate at 166-263 kg/ha (N2) provided sufficient N for a 4-6-year-old pomegranate orchard and that high-frequency SDI is a promising technology for achieving higher N use efficiency and minimizing leaching loss of NO 3 − and DOC.

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.…”

“…Overall, the lower soil N 2 O concentration in SDI plots than that from DI may also be due to more efficient plant uptake. Tirado-Corbalá et al [18] showed that total N uptake in fruits were significantly higher in SDI plots than that from DI at least for two out of three years. 2013 data (not shown) were similar to those collected in 2012 in distribution patterns except that the N3 treatment plots showed either lower or similar N 2 O concentrations as the N2 treatment plots that were consistent with the emission data.…”

“…The data support that microbial reactions could occur in subsurface and explained why N 2 O concentration could increase with soil depth in subsurface soil under SDI. 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.…”

“…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.…”

“…These were due to N application at surface for DI, but in subsurface for SDI. Tirado-Corbalá et al [18] showed that dissolved organic carbon (DOC) and nitrate concentrations under the SDI were higher in subsurface soils (below 30 cm) than surface soil compared to those under DI with higher concentrations in upper soil depths. The data support that microbial reactions could occur in subsurface and explained why N 2 O concentration could increase with soil depth in subsurface soil under SDI.…”