Document Type : Research Paper
Authors
1 Agricultural Engineering Research Department, Ardabil Agricultural and Natural Resources Research and Education Center, Agricultural Research, Education and Extension Organization, Ardabil, Iran.
2 Agricultural Engineering Research Institute, Agricultural Research, Education and Extension Organization (AREEO), Karaj, Iran
Abstract
Keywords
Main Subjects
Seasonal Irrigation Performance Assessment in Peaches and Nectarines Orchards (a Case Study: Ardabil Province, Iran)
EXTENDED ABSTRACT
Economical fruit trees have become an important cash source of many rural household incomes. However, in arid and semi-arid regions, serious water resource challenges due to changing climate and the rapid expansion of the population are the biggest challenge to the viability and sustainability of the horticulture sector. Improving irrigation water management in orchards in the Ardabil Province of Iran is an increasingly important issue, especially given the low water allocations and concerns about drought events in recent years. In this regard, irrigation performance assessments under actual operation conditions are required as a first step toward improving agricultural water management. Hence, the objective of this work was to assess the seasonal irrigation performance of peaches and nectarines (Prunus Persica L.) under actual operation conditions by monitoring 24 orchards in Ardabil Province, Iran, during the growing season 2018-2019. This study was carried out in Parsabad and Meshginshahr counties, as the main peach- and nectarine-producing regions of the province.
The study orchards were selected in such a way as to cover, as much as possible, the range of peach and nectarine orchards' properties in terms of physical-chemical properties of soil and irrigation water, orchard surface area, irrigation method, tree spacing, tree cultivar/age, orchardist's education and skill (advanced/ordinary) level. During the field studies, soil texture and salinity, irrigation water salinity, irrigation schedule, tree growth stages, and fruit yield were determined. The applied irrigation water depth (I) for each of the irrigation events was estimated by measuring the flow rate delivered to the orchard, the irrigation duration, and the actual cultivated orchard area. Crop water requirement, ETc, was determined by the FAO Penman-Monteith model, using weather data obtained from the nearby synoptic sites, including Parsabad (lat. 39⁰36’ N, long. 47⁰46’E) and Meshginshahr (lat. 38⁰22’ N, long. 47⁰40’E). Effective precipitation, Pe, was estimated, using the USDA-SCS method. The seasonal irrigation performance was evaluated, using the following six performance indicators: relative rainfall supply (RRS = Pe / ETc), relative irrigation supply (RIS = I / [ETc - Pe]), crop yield ratio (CYR, the ratio of actual to intend fruit yield), applied water productivity (WPI), water productivity (WPI+Pe), and economic water productivity (WP$). The intended fruit yield for each of the study orchards was considered as the third quarter of the fruit yield during the last five years.
The seasonal estimates of the net irrigation requirement (In = ETc - Pe) during the growing season 2018-2019 and its 10-year average ranged from 567-721 mm and 544-697 mm, respectively, over the study orchards. The seasonal I + Pe and the fruit yield ranged from 280-1675 mm and 1.00-32.43 ton ha-1 (with a weighted average, WA, of 582 mm and 14.61 ton ha-1), respectively. RRS and RIS ranged from 0.08-0.15 and 0.96-2.35, with WA of 0.09 and 1.25, respectively. CYR ranged between 0.17-1.25 (with a WA of 0.95). The mean RIS over initial, development, mid-, and late-season growth stages were 1.09, 1.80, 1.61, and 0.05, respectively. These results indicate that the study orchards experienced varying degrees of over-/under-irrigation. The mean RIS for the drip irrigation method (1.25) was significantly (P < 0.05) lower than the surface irrigation method (1.66). WPI and WPI+Pe ranged from 0.11-6.81 and 0.11-5.04 kg m-3, with a WA of 2.77 and 2.44 kg m-3, respectively. WP$ range from -42.60 × 103 to 246.27 × 103 Rial m-3 with a WA of 56.41 × 103 Rial m-3. WPI, WPI+Pe, and WP$ indicators were significantly (P < 0.05) affected by the orchardist's skill level, interplantion of trees, tree spacing, irrigation method, and disease/frost (DF) damage. Post-harvest period accounted for a mean proportion of 75, 25, and 15% of the seasonal applied water in orchards with early-season, late-season, and mixed early- and late-season cultivars, respectively. Compared to surface irrigation, drip irrigation did not necessarily lead to an increase in fruit yield, but the use of drip irrigation resulted in a significant improvement in water productivity indicators. DF damage accounted for an 87 and 85% reduction in fruit yield and WPI+Pe, respectively, compared to the orchards without severe DF damage.
Under the current technological and economic constraints, most of the study orchards experienced a rational (but yet with low productivity) irrigation water management. Improving irrigation efficiency and fruit yield, controlling disease/frost damage, and Implementing regulated deficit irrigation during pre- and post-harvest stages are the most effective approaches to improve water productivity indicators in the study area.