Environmentally Sound Irrigation and Fertility Systems for Sweet Cherry Crops in the Pacific Northwest

View the project final report

Commodities

• Fruits: cherries

Practices

• Crop Production: fertigation, irrigation
• Education and Training: display, extension
• Farm Business Management: feasibility study, agricultural finance
• Pest Management: biological control, economic threshold
• Sustainable Communities: partnerships, sustainability measures

The objective of this project was to evaluate the impacts of drip irrigation, split N fertigation, and ground covers on water consumption, N use, and fruit productivity of sweet cherry. A field experiment was conducted using ‘Lapins’ sweet cherry at The Dalles, OR in 2005 and 2006. Two irrigation systems (single-line drip irrigation and micro sprinkler irrigation) and four ground management systems [straw mulch, white polypropylene cover, black polypropylene cover, and control (no mulch or polypropylene cover, but herbicides were used to control weeds)] were evaluated in a split-plot design with four replicates. Another field trial was implemented on ‘Regina’ cherry trees at Hood River, OR in 2006 and 2007. Five N fertigation and irrigation systems [1. control (micro sprinkler + broadcast application of dry N fertilizer on the soil surface), 2. micro sprinkler irrigation + fertigation of N fertilizer injected at the same time and interval as irrigation, 3. drip irrigation every day + fertigation of N fertilizer every day, 4. drip irrigation every two days + fertigation of N fertilizer every two days, and 5. drip irrigation every four days + fertigation of N fertilizer every four days] were evaluated in a randomized complete block design with four replicates.

Our two-year results at The Dalles showed the biggest benefit with drip irrigation was water saving. During the entire season from May to September each year, drip irrigation consumed only 21 to 26% of irrigation water relative to micro sprinkler irrigation. Black polypropylene, white polypropylene, and straw mulch covers reduced irrigation water use slightly compared with no cover. Fruit yield was statistically similar under drip irrigation and micro sprinkler. There was a trend of yield increase with straw mulch and polypropylene covers relative to no cover. Fruit quality including firmness, color, and size did not differ regardless of irrigation or ground cover system. Drip irrigation increased marketable fruit by about 4-5% (absolute value) via reducing fruit surface pitting compared with micro sprinkler. Overall, drip irrigation seems to be a good system for orchards in regions that are short of water.

At Hood River in both years, micro sprinkler irrigation plus N fertigation system resulted in significantly higher leaf N concentrations than micro sprinkler plus dry N fertilizer system after harvest. However, no increase in leaf nutrient concentrations was observed with the three drip irrigation plus N fertigation systems compared with micro sprinkler plus dry N fertilizer system. The three drip irrigation plus fertigation treatments saved over 60% of irrigation water per season relative to the two micro sprinkler treatments. Fruit yield and quality were statistically similar among the five irrigation and N management systems. Overall, drip irrigation plus N fertigation systems produce competitive sweet cherries with much less irrigation water and provide more flexibility for N fertilizer applications.

The impacts of this project on sweet cherry productivity and profitability and the environment were significant, and will be greater. About 300 targeted sweet cherry growers along with thousands of other fruit growers were educated through this project. More and more growers in the Pacific Northwest have begun to use drip irrigation, ground covers, and N fertigation on their orchards, and this trend will be magnified during the next 5 to 10 years.

Introduction

Oregon’s Mid-Columbia region boasts the highest concentration of cherry orchards in the United States. Production of sweet cherry is highly dependent on the inputs of water and nitrogen (N) fertilizer to achieve optimum yields in the Pacific Northwest. Currently, impact and micro sprinklers are the primary form of irrigation. Nitrogen fertilizer is broadcast applied on soil surface as a dry material once or twice per year. Both water and N use efficiencies are low under these management practices. Overall, the current water and N management practices have resulted in high production costs and low grower profitability, and contaminated streams and rivers due to increased N leaching losses from the soil. Furthermore, there is increasing concern about the adverse impacts of current water and N management practices on fruit quality and the storability of sweet cherry. Therefore, research is needed to develop more efficient irrigation and N management systems.

So far, little research has been done to address the effects of drip irrigation and fertigation on growth, yield, quality, and storability of orchard trees. On the other hand, enhanced yields, higher water and N use efficiencies, and improved control of weeds are reported with both drip irrigation and fertigation on some non orchard crops. For example, drip irrigation increased sweet pepper yield by 50% compared with micro sprinkler (Goyal et al., 1987). Water consumption was reduced by as much as 50% with drip irrigation relative to micro sprinkler in potato production (Waddell et al., 1999). Nitrogen use efficiency was enhanced by above 20% relative to broadcasting of dry N fertilizer to the soil surface on citrus trees (Sauls, 2004). In addition, water management is highly related to fruit quality and storability. For instance, excessive application of water or prolonged water uptake by the fruit can cause sweet cherry surface pitting (Patten et al., 2004). However, drip-irrigation and fertigation have not been tested either separately or as an integrated production system on sweet cherry in the Northwest. No guidelines are available about water and N management for drip irrigated or (and) fertigated sweet cherry.

Ground management is another key practice in sweet cherry production. Growers overwhelmly use herbicides to control weeds at present. However, herbicides are quite expensive and may hurt soil ecosystems and cause water contamination. Although no publications about polypropylene and straw mulch ground covers on sweet cherry are available, some research about mulch cover has been done on apple, and the results are encouraging. Mervin and Stiles (1994) reported that trunk cross-sectional area and fruit yield of apple were significantly enhanced due to mulch cover compared with no ground cover but with herbicide applications. Soil water availability, soil organic matter, water infiltration, saturated hydraulic conductivity, and soil temperatures were improved by mulch cover (Merwin et al., 1994). In addition, nitrate-N and benomyl fungicide leaching and runoff were reduced due to mulch cover relative to no cover but with herbicide applications (Mervin et al., 1996). All these results suggest orchard productivity, soil fertility, and soil quality are improved due to straw mulch ground cover. However, no research has been done to compare all these different ground cover management options simultaneously under different irrigation systems.

The objectives of this project were to: 1) examine the impacts of drip irrigation and N fertigation systems on sweet cherry water and N use compared with micro-sprinkler irrigation and broadcast application of dry N fertilizer systems; 2) evaluate the effects of drip irrigation and fertigation systems on fruit yield, quality, and storability of sweet cherry; and 3) compare the effects of different ground cover systems (straw mulch, white polypropylene, black polypropylene, and no cover but with herbicide applications) on fruit yield, quality, storability, and water use of sweet cherry.