1. Responses of Sweet Cherry Productivity and Soil Quality to Alternate Groundcover and Irrigation Systems Xinhua Yin 1, Xiaolan Huang 1, and Lynn Long 2 1 Department of Plant Sciences, University of Tennessee, Knoxville, TN 37996 2 Department of Horticulture, Oregon State University, Corvallis, OR 97331 INTRODUCTION Sweet cherry production is highly dependent on water and ground management to achieve high yields (Glover et al., 2000; Granatstein and Mullinix, 2008). Oregon produces over 20% of the sweet cherries in the United States (Yin et al., 2007). Presently, impact and micro sprinkler systems are the primary forms of irrigation in Oregon. These irrigation systems wet 100% of orchard ground surface by providing water to both the tree rows and between-row grasses. It has shown that water use efficiency is below optimal under these irrigation systems. Additionally, there is increasing concern about the adverse impacts of the current irrigation systems on fruit quality and storability of sweet cherry. Using crop straw to cover the row areas beneath orchard trees is emerging as an in-row ground management alternative to the traditional practice of no ground cover but with herbicide applications for weed control (Glover et al., 2000; Verdu and Mas, 2007). Therefore, alternate irrigation and ground cover systems are needed for profitable and sustainable sweet cherry production. RESULTS AND DISCUSSION Irrigation Water Consumption and Fruit Yield Seasonal irrigation water consumption under the traditional MSR ranged from 7305 to 8512 Mg ha -1 for the three years with an average of 7792 Mg ha -1, whereas the corresponding value for DDR ranged from 3159 to 3828 Mg ha -1 averaging 3562 Mg ha -1 (Fig. 1a). Straw mulch reduced seasonal water use in 2007 compared with NC (Fig. 1b). No interactions between irrigation and ground cover systems were observed. Total and marketable fruit yields at harvest did not differ between the two irrigation or ground cover systems in any season (Fig. 2a, 2b). Productivity of irrigation water differed with treatment. One mm of irrigation water produced 2.8 to 7.6 kg ha -1 fruit under DDR, about 1.7 to 2.4 times greater than that with MSR. (Fig. 3a). Straw mulch improved the productivity of irrigated water in 2007 (Fig. 3b). Fruit Quality and Storability Fruit quality including size, firmness, titratable acidity, and sugar content at harvest or after 3-week cold storage did not differ regardless of irrigation or ground cover system (data not presented). Leaf Nutrient Concentrations after Fruit Harvest Leaf P concentrations were lower with DDR than MSR each year with an average decrease of 30% (data not presented). Leaf Zn levels were lower under DDR than MSR in 2006 and 2007 with a reduction of 15.6 to 19.3%. Leaf nutrient concentrations did not differ between the two ground cover systems (data not presented). Soil Biology at the End of Experimentation Soil active and total fungi and total bacteria differed between the two irrigation and ground cover systems (Table 1). Soil protozoa including flagellates and soil nematodes as well were different for the two irrigation and ground cover systems (Tables 2 & 3). OBJECTIVE To evaluate the main and interactive effects of straw mulching and drip irrigation on tree growth, fruit yield, quality, and storability of sweet cherry compared with those of the current no ground cover (but with herbicide applications) and micro sprinkler irrigation systems. CONCLUSIONS Double-line drip irrigation reduced seasonal irrigation water consumption by 50-57% compared with MSR. Straw mulch lowered irrigation water use by 5-16% relative to NC. Total and marketable fruit yields were similar for the two irrigation and ground cover systems. Productivity of irrigation water was substantially enhanced with DDR relative to MSR. Fruit quality at harvest or after 3-week cold storage did not differ regardless of irrigation and ground cover system. Soil bacteria, fungi, protozoa, and nematodes were mostly affected by drip irrigation and straw mulch. ACKNOWLEDGMENTS Research was supported by USDA NRCS CIG Program, Northwest Sweet Cherry Commission, and Oregon State University Agricultural Research Foundation. MATERIALS AND METHODS Field Experiment A field trial was conducted on bearing Lapins sweet cherry trees on the Omeg Orchards near The Dalles, OR from 2006 to 2008. Micro sprinkler irrigation and no ground cover (but with herbicide applications for weed control) were used to manage this orchard block prior to the implementation of this trial. Two irrigation systems [double-line drip irrigation (DDR), micro sprinkler irrigation (MSR)] and two ground management systems [wheat straw mulch cover (SM), and control (NC) (no mulch or fabric cover, but herbicides were used to control weeds)] were assigned to the main and split plots, respectively, in a randomized complete block split-plot design with four replications. Soil moisture was monitored weekly at a 30-cm depth from May to Oct. for each plot. Irrigation scheduling for each plot was based on soil moisture content, and each plot was irrigated separately. Measurement Soil moisture; weekly and seasonal irrigation water consumption Leaf N, P, K, Ca, Mg, S, B, Zn, Mn, & Cu concentrations Fruit yield; fruit size, firmness, color, sugar, & titratable acidity at harvest Fruit surface pitting and marketable fruit yield Soil available N, P, K, Ca, Mg, S, B, Zn, Mn, & Cu contents, pH, & OM Soil active and total bacteria, fungi, protozoa, & nematodes at the end of experimentation Statistical Analysis Analysis of variance (ANOVA) was conducted for each measurement in a randomized complete block split-plot design for each year using the SAS statistical software. Probability levels less than 0.05 were designated as significant. REFERENCES Glover, J.D., J.P. Reganold, and P.K. Andrews. 2000. Systematic method for rating soil quality of conventional, organic, and integrated apple orchards in Washington State. Agriculture Ecosystems & Environment 80:29-45. Granatstein, D., and K. Mullinix. 2008. Mulching options for northwest organic and conventional orchards. HortSci. 43:45-50. Verdu, A.M., and M.T. Mas. 2007. Mulching as an alternative technique for weed management in mandarin orchard tree rows. Agronomy for Sustainable Development 27:367-375. Yin, X.H., C.F. Seavert, R. Núñez-Elisea, J. Turner, and H. Cahn. 2007. Effects of polypropylene groundcover on soil nutrient availability, sweet cherry nutrition, and cash costs and returns HortSci. 42:147-151. a b b a Fig. 1a Fig. 2a Fig. 3a Fig. 1b Fig. 3b Table 1. Effects of irrigation and ground cover systems on soil microbiology (Mar. 2009). Table 2. Effects of irrigation and ground cover systems on soil protozoa (Mar. 2009). Treatment Bact- Feeders Fungal- Feeders Root- Feeders Predatory Total Nematodes DDR0.34 Table 3 Effects of irrigation and ground cover systems on soil nematodes (Mar. 2009). 0.054 0.0260.0040.42 MSR0.220.0240.0430.0080.29 Significance***** NC0.230.0300.0460.0030.30 SM0.330.0480.0250.0080.41 Significance***** TreatmentFlagellatesAmoebaCiliates DDR165.01902.99.9 MSR303.51827.09.6 Significance*ns NC313.73131.68.9 SM154.7598.310.7 Significance**ns