Conventional, and Integrated Apple Production Systems in Washington. State, USA ... Organic soil management practices have included additions of composted ...
Soil and Plant Mineral Nutrition and Fruit Quality under Organic, Conventional, and Integrated Apple Production Systems in Washington State, USA Preston K. Andrews and John K. Fellman Dept. of Horticulture and Landscape Architecture Washington State University Pullman, Washington 99164-6414 USA
Jerry D. Glover and John P. Reganold Dept. of Crops and Soil Sciences Washington State University Pullman, Washington 99164-6420 USA
Keywords: calcium, Malus x domestica, nitrogen, post-harvest storage, orchard floor management Abstract A 1.6-hectare study site, planted in 1994 at a commercial apple orchard in Washington state, USA, consisted of four replicate plots of each of the following three apple (Malus x domestica Borkh. cv. 'Golden Delicious') production systems: organic, conventional, and integrated. One objective of this study was to assess the long-term effects of these production systems on soil/plant mineral nutrient relations and fruit quality. Organic soil management practices have included additions of composted poultry manure and bark mulches, woven polypropylene fabric, and mechanical tillage for weed control. Conventional soil management practices included synthetic fertilizers and herbicides for weed control. The integrated treatment utilized a combination of organic and conventional practices. After five years under these production systems, total topsoil N was significantly higher in the organic and integrated systems compared to the conventional system, although nitrate N was lowest in the organic system. Even though these differences in available soil N have not led to differences in leaf N among the three systems, the lower available soil N in the organic system is associated with significantly lower fruit tissue N. Fruit Ca contents have consistently risen in all three production systems over the four cropping years. In addition, there were significant differences in fruit nutrient ratios among the three systems. These differences are discussed in terms of fruit quality under the varying soil management practices inherent among organic, conventional, and integrated apple production systems. INTRODUCTION As orchard production in Washington State has intensified to meet market demands over the past decades, environmental concerns associated with conventional management practices have also increased (Williamson et al, 1998). These concerns have led to heightened interest in developing environmentally sound management practices. Organic and integrated apple production systems offer alternative practices that address environmental concerns (Conacher and Conacher, 1998; National Research Council, 1989). Organic management practices exclude synthetic chemical pesticide and fertilizer inputs and use naturally derived products as defined by organic certification programs. Integrated farming systems, successfully adopted in some of the major apple growing regions of Europe (Sansavini, 1997), utilize methods of conventional and organic production systems in an attempt to optimize both environmental quality and economic profit. Although studies have found that alternative production practices may improve soil quality as compared to conventional practices (Glover et al., 2000; Gunapala and Scow, 1998; Reganold et al., 1987, 1993; Swezey et al., 1998), to our knowledge no study has specifically compared the effects of conventional, organic, and integrated apple production systems on soil and plant mineral nutrition as well as fruit quality.
Proc. IV IS on Mineral Nutrition in Fruit Eds. D. & G. Neilsen, Fallahi & Peryea Acta Hort. 564, ISHS 2001
291
MATERIALS AND METHODS Four 0.14-ha replicate plots of organic, conventional, and integrated production systems were planted in May 1994 in a randomized complete block design on a commercial 'Golden Delicious'/M.9 apple orchard in the Yakima Valley of Washington state, USA (latitude 46°30'N). Each plot contains four rows trained to a two-wire trellis system. Trees were planted at a spacing of 1.2 m between trees and 3 m between rows (2240 trees/ha). A 2-m wide weed-free strip in the tree rows was maintained for all systems according to weed management practices described later. The alleyways consist of mown turf grass. The 200 mm of annual precipitation at the site is supplemented with an under-tree sprinkler irrigation system. Soil in the study area is of a sandy loam texture. Organic production practices included bark mulch and landscape fabric for weed control in 1994-96 and cultivation in the 1997-99 growing seasons (Table 1). Nutrients for the organic system were supplied in the form of composted poultry manure and as organically certified foliar sprays. Certified biological pest control methods were also used in the organic system. Conventional production practices included synthetic soil and foliar fertilizer applications and chemical control of weeds. The integrated production system included some practices from the organic and conventional production systems that were deemed to be profitable and environmentally sound. Nutrients for the integrated system were supplied partly as composted poultry manure and partly as synthetic fertilizer. Pest management practices were identical in both the integrated and conventional systems, and included pheromone-mating disruption to control codling moth (Cydia pomonella). Flower and fruit thinning was by hand in the organic system and with chemicals in the conventional and integrated systems. Soil samples were taken at 0-15 and 15-30 cm depths from each of the designated plots following planting of the trees, but prior to implementation of the treatment production systems. These pre-treatment samples and subsequent annual soil samples were taken each May midway between trees within the tree rows. Soil samples were analyzed for total N, nitrate N, and extractable P, K, Mg and Ca according to standard procedures (Page, 1982). Analyses of the pre-treatment soil samples revealed no differences in physical, chemical, or biological soil properties among plots at planting (Hopkins-Clark, 1995). For plant tissue analyses, random pooled samples of mid-shoot leaves and uniformly sized fruit were collected from each plot annually in midsummer (leaves) or three weeks prior to expected harvest (fruit). Leaf and fruit mineral element contents (N, P, K, Ca, and Mg) were determined according to standard methods (Gavlak et al., 1994). To minimize edge effects, all soil and plant samples were taken from interior-facing sides of trees in the middle two rows of each plot. Fruit firmness, soluble solids, and acidity were analyzed according to standard procedures (Apple Maturity Program Handbook, 1986) at harvest and after three and six months of regular and controlled atmosphere, refrigerated storage in 1998 and 1999. Untrained sensory panels were used to determine preferences for sweetness, tartness, and firmness of 1999 fruits from each production system and storage treatment. RESULTS Total soil N was higher in the integrated production system than in either of the other two systems in 199S, and higher than in the conventional system in 1999 (Table 2). Similar differences were found among systems for extractable soil P in these years. Nitrate N was lowest in the organic system in both years. Soil K contents were higher in both the organic and integrated systems than in the conventional system in 1998, but there were no differences among systems in 1999. Soil Ca and Mg contents were not different among systems in either 1998 or 1999. Soil mineral nutrient contents are not reported at the 15-30 cm depth, because there were only a few differences found among the treatments. There were few differences in leaf tissue mineral contents among the three production systems in 1998 or 1999. The organic system had lower K contents than the other two systems in 1998, and higher P contents in 1999 (Table 3).
292
Fruit cortical N concentration was lowest in the organic production system in both 1998 and 1999 (Table 4). There were no differences among systems in fruit P in 1998, and in fruit K, Mg, and Ca in either year, although fruit Ca has doubled since 1995 (data not shown). Phosphorus concentration was lowest in the organic fruit in 1999. Fruit B concentration was lower in the organic system than in the conventional system in 1998, and in the organic and integrated systems in 1999. Ratios of fruit cortical nutrient contents were calculated. In 1998, the N:Ca ratio was higher in the integrated production system (9.8) than in either the organic (6.5) or conventional (6.5) systems. In 1999, the N:Ca ratios among the production systems were not different; however, the N:P ratio was higher in. the conventional (5.1) and integrated (5.4) systems than in the organic (4.2) system. Other fruit cortical nutrient ratios, such as, Mg:Ca, K:Ca, and Mg+K:Ca, were not different among the systems in either year (data not shown). Organic fruit were firmer at harvest and immediately after removal from either regular (RA) or controlled (CA) atmosphere storage than fruit produced in the conventional system (Table 5). There were no differences in fruit firmness among the three systems after 7 days in air at 20°C following removal from either storage regime. Similar differences in fruit firmness between the systems and storage regimes were found in 1998 (data not shown). In 1999, organic (Org) fruit were significantly (P=0.05) firmer than conventional (Con) fruit after six months CA storage, either immediately after removal from storage (Org = 54.8 N, Con = 52.3 N) or after 7 days in air at 20°C (Org = 56.4 N, Con = 53.4 N). Fruit from the organic system had higher soluble solids than the conventional fruit either immediately after removal from three months of CA storage or after 7 days in air at 20°C (Table 5). Organic fruit also had lower acidity than the conventional fruit, except immediately after removal from CA storage. The higher soluble solids and lower acidity in organic fruit resulted in higher soluble solids:acidity ratios than either conventional or integrated fruit (data not shown). An untrained sensory panel confirmed the differences in sweetness versus tartness of organic and conventional fruit, whereas the panel did not identify firmness differences (data not shown). DISCUSSION We observed significant differences in total and nitrate soil N among our three production systems four years after the last soil applications of N fertilizers (Tables 1 and 2). Swezey et al. (1998) found no differences in soil N concentrations or in the concentrations of any other soil nutrient, two years after their study of organic and conventional apple production systems was initiated, despite the annual application of 60 and 85 kg N/ha to these systems, respectively. In a New Zealand study, total soil N concentration was higher in an organic system than in either conventional or integrated systems (Goh et al., 2000). They attributed the higher soil N to greater biological fixation in the vegetation of the organic system. They also reported greater biomass carbon in their organic system than in their conventional or integrated systems; however, we measured the greatest biomass carbon in our integrated system (Glover et al., 2000). These differences in total and available N may be due to variations in the C:N ratio of fertilizer inputs and rate of N mineralization in these three systems. We observed no relationship between treatment differences in soil nutrient contents and mid-summer leaf nutrient concentrations (Tables 2 and 3). Although Swezey et al. (1998) did not find differences in soil nutrient contents between their organic and conventional systems, they did find differences in mid-summer leaf N, P, K, Ca, and B concentrations. They attributed differences in N, K, and Ca concentrations to increased competition from weeds and fruit load in the organic system. Although Neilsen et al. (1986) found higher N concentrations in apple leaves from trees mulched with black plastic, they found higher leaf P and K concentrations in trees having a full cover of mowed grass sod. These differences in leaf nutrient concentrations were attributed to differences in nutrient mobilization and recycling (Neilsen and Hogue, 1985). Only apple leaf K concentrations were higher when an herbicide-free strip in the tree row was
293
maintained just until mid-July, compared with year round weed control (Neilsen et al., 1999). Marsh et al. (1996) also found that leguminous cover crops or applications of compost or organic mulch increased apple leaf N and K. concentrations. Neilsen and Edwards (1982) found no relationship between soil and apple leaf K and Ca concentrations. Therefore, depending upon soil properties and competition from either weeds or fruit load, leaf nutrient analyses may or may not reflect differences in soil nutrient contents in some perennial fruit crop production systems. We have not found any studies that have examined the relationship between soil and/or leaf nutrient contents and fruit nutrient concentrations and fruit quality under alternative apple production practices. For those soil nutrients with significant differences among our three production systems, only soil N (especially nitrate N) was positively related to fruit tissue N (Tables 2 and 4). No apparent relationships existed between nutrients in leaves and fruit (Table 3 and 4). DeEll and Prange (1993) also found lower N, but higher P and K concentrations, in organic fruit than in conventional fruit. In a six-year study of N fertilizer rates and weed control duration, Neilsen et al. (1999) found few direct relationships between leaf and fruit N, E, or K concentrations. Organic fruit were firmer and sweeter than fruit from the conventional or integrated systems (Table 5). Despite finding significant differences between the production systems in N:Ca ratios in 1998 and N:P ratios in 1999, there were no consistent relationships between fruit nutrient concentration ratios and fruit quality. Wolk et al. (1998) found no consistent year-to-year relationships between fruit N, P, K, Mg, or Ca and storage disorders of 'Golden Delicious' apples. Fruit quality was most consistently related to fruit N concentrations in our study (Tables 4 and 5). Indeed, reductions in apple fruit firmness, soluble solids, and storage potential because of excess N have been documented (Hipps and Perring, 1989; Ystaas and Frøynes., 1991). Under commercial conditions, it may be unnecessary or even undesirable, to annually apply certain nutrients, especially N, to perennial fruit crop systems. Lower soil and fruit N concentrations can be maintained in organic production systems, which may favor fruit quality attributes that are important to successful apple marketing. ACKNOWLEDGEMENTS We thank the farmers A. Dolph and E. Dolph for the use of their farm and Dr. J.R. Powers for conducting the sensory panel evaluations. We gratefully acknowledge funding from the United States Department of Agriculture's Agricultural Systems Program. Literature Cited Apple Maturity Program Handbook. 1986. Apple Maturity Program, Wenatchee, Washington, USA Conacher, J. and Conacher, A. 1998. Organic farming and the environment, with particular reference to Australia: a review. Biol. Agric. Hort. 16: 145-171 DeEll, J.R. and Prange, R.K. 1993. Postharvest physiological disorders, diseases and mineral concentrations of organically and conventionally grown McIntosh and Cortland apples. Can. J. Plant Sci. 73: 223-230 Gavlak, R.G., Horneck, D.A. and Miller, R.O. 1994. Plant, soil and water reference methods for the western region. West. Reg. Pub. 125, Univ. Alaska Cooperative Extension Service, Fairbanks, Alaska, USA Glover, J.D., Reganold, J.P. and Andrews, P.K. 2000. Systematic method for rating soil quality of conventional, organic, and integrated apple orchards in Washington State. Agric. Ecosystems Env. 80: 29-45 Goh, K.M., Bruce, G.E., Daly, M.J. and Frampton, C.M.A., 2000. Sensitive indicators of soil organic matter sustainability in orchard floors of organic, conventional and integrated apple orchards in New Zealand. Biol. Agric. Hort. 17: 197-205 Gunapala, N. and Scow, K.M., 1998. Dynamics of soil microbial biomass and activity in conventional and organic farming systems. Soil Biol. Biochem. 30: 805-816 Hipps, N.A. and Perring, M.A. 1989. Effects of soil management systems and nitrogen
294
fertilizer on the firmness and mean fruit weight of Cox's Orange Pippin apples at harvest. J. Sci. Food Agric. 48: 507-510 Hopkins-Clark, J.S. 1995. A comparison of organic, integrated and conventional soil management systems in a commercial apple orchard. M.S. Thesis, Department of Horticulture and Landscape Architecture, Washington State University, Pullman, Washington, USA Marsh, K.B., Daly, M.J. and McCarthy, T.P. 1996. The effect of understorey management on soil fertility, tree nutrition, fruit production and apple fruit quality. Biol. Agric. Hort. 13: 161-173 National Research Council, 1989. Alternative agriculture. National Academy of Sciences, Washington, D.C., USA Neilsen, G.H. and Edwards, T. 1982. Relationship between Ca, Mg, and K in soil, leaf, and fruits of Okanagan apple orchards. Can. J. Soil Sci. 62: 365-374 Neilsen, G.H. and Hogue, E.J. 1985. Effects of orchard soil management on the growth and leaf nutrient concentration of young dwarf Red Delicious apple trees. Can. J. Soil Sci. 65: 309-315 Neilsen, G.H., Hogue, E.J. and Drought, B.G. 1986. The effect of soil management on soil temperature and apple tree nutrition. Can J. Soil Sci. 66: 701-711 Neilsen, G.H., Hogue, E.J. and Meheriuk, M.J. 1999. Nitrogen fertilization and orchardfloor vegetation management affect growth, nutrition and fruit quality of Gala apple. Can. J. Plant Sci. 79: 379-385 Page, A.L. (ed.). 1982. Methods of soil analysis, Part 2. 2nd edition. Amer. Soc. Agron., Madison, Wisconsin, USA Reganold, J.P., Elliott, L.F. and Unger Y.L., 1987. Long-term effects of organic and conventional farming on soil erosion. Nature 330: 370-372 Reganold, J.P., Palmer, A.S., Lockhart, J.C. and Macgregor, A.N. 1993. Soil quality and financial performance of biodynamic and conventional farms in New Zealand. Science 260: 344-349 Sansavini, S. 1997. Integrated fruit production in Europe: research and strategies for a sustainable industry. Scientia Horticulturae 68: 25-36 Swezey, S.L., Werner, M.R., Buchanan, M. and Allison, J. 1998. Comparison of conventional and organic apple production systems during three years of conversion to organic management in coastal California. Amer. J. Alternative Agric. 13: 162-180 Williamson, K.K., Munn, M.D., Ryker, S.J., Wagner, R.J., Ebbert, J.C. and Vanderpool, A.M. 1998. Water quality in the Central Columbia Plateau., Washington and Idaho, 1992-1995. U.S. Geological Survey Circular 1144, on line at http://water.usgs.gov/lookup/get?circ1144, updated March 3, 1998 Wolk, W.D., Lau, O.L., Neilsen, G.H. and Drought, B.G. 1998. Factors and time of sample collection for correlating storage potential of 'McIntosh', 'Spartan', and 'Golden Delicious' apples. J. Amer. Soc. Hort. Sci. 123: 104-109 Ystaas, J. and Frøynes, O. 1991. Nitrogen and potassium nutrition of 'Aroma' apples: effects of different N and K applications on yield, fruit size and fruit quality. Norw. J. Agric. Sci. 5: 385-391
295
Tables
Table 1. Nutrient and weed management practices of organic, conventional, and integrated apple production systems. Year
Organic
Conventional
Integrated
1994 1995 1996 1997 1998 1999
Poultry compostz Poultry compostz Ca, B, Zn, SO4 y Cay Ca, By Ca, By
Nutrient Management Ca(NO3 )2 z Ca(NO3 )2 z, 3-18-18y , ureay 3-18-18, Ca, B, Zn, SO4 y 3-18-18, Ca, Zny 3-18-18, Ca, B, Zny 3-18-18, Ca, B, Zny
50:50z 50:50 , 3-18-18y , ureay 3-18-18, Ca, B, Zn, SO4 y 3-18-18, Ca, Zny 3-18-18, Ca, B, Zny 3-18-18, Ca, B, Zny z
Weed Management 1994 Bark mulch Glyphosate Bark mulch, glyphosate 1995 Bark mulch Glyphosate Bark mulch, glyphosate 1996 Woven fabric Glyphosate, simazine Glyphosate 1997 Woven fabric Glyphosate, simazine Glyphosate 1998 Cultivation Glyphosate, simazine Glyphosate 1999 Cultivation Glyphosate, simazine Glyphosate z Ground application of 29 kg N/ha as composted poultry manure, Ca(NO3 )2 , or 50:50 of both y Foliar applications
Table 2. Soil mineral nutrient contents (0-15 cm depth) of organic, conventional, and integrated apple production systems Nutrient (units)
Organic
Conventional
Integrated
Total N (kg/ha) Nitrate N (mg/kg) P (mg/kg) K (mg/kg) Mg (meq/100 g) Ca (meq/100 g)
2643 bz 8.0 c 51.6 a 573 a 3.8 a 9.9 a
1998 2588 b 14.0 b 42.1 b 482 b 3.4 a 9.8 a
3078 a 20.6 a 56.1 a 586 a 3.4 a 9.4 a
1999 Total N (kg/ha) 2712 ab 2039 b Nitrate N (mg/kg) 2.3 b 14.0 a P (mg/kg) 40.8 b 46.8 b K (mg/kg) 480 a 475 a Mg (meq/100 g) 4.7 a 4.3 a Ca (meq/100 g) 10.2 a 10.3 a z Mean separation within rows by protected LSD at the 5% level
296
2956 a 17.3 a 61.6 a 570 a 4.5 a 10.2 a
Table 3. Leaf nutrient concentrations of organic, conventional, and integrated apple production systems. Nutrient (%DWz) N P K Mg Ca
Organic
Conventional
Integrated
2.2 ay 0.16 a 1.4 b 0.38 a 1.7 a
1998 2.4 a 0.16 a 1.7 a 0.40 a 2.1 a
2.3 a 0.16 a 1.8 a 0.40 a 1.9 a
1999 N 2.2 a 2.4 a P 0.21 a 0.18 ab K 1.8 a 1.8 a Mg 0.33 a 0.31 a Ca 1.8 a 1.9 a z DW = dry weight y Mean separation within rows by protected LSD at the 5% level
2.4 a 0.16 a 1.9 a 0.33 a 1.9 a
Table 4. Fruit cortical nutrient concentrations of organic, conventional, and integrated apple production systems Nutrient (%DWz)
Organic
Conventional
Integrated
N P K Mg Ca B
0.40 bz 0.09 a 0.82 a 0.04 a 0.06 a 5.0 b
1998 0.46 ab 0.10 a 0.90 a 0.05 a 0.07 a 7.0 ab
0.54 a 0.10 a 0.85 a 0.04 a 0.06 a 7.2 a
1999 N 0.30 b 0.40 a P 0.072 b 0.080 a K 0.80 a 0.88 a Mg 0.04 a 0.05 a Ca 0.10 a 0.10 a B 7.8 b 11.5 a z DW = dry weight y Mean separation within rows by protected LSD at the 5% level
0.41 a 0.075 ab 0.88 a 0.05 a 0.09 a 7.5 b
297
Table 5. Fruit firmness, soluble solids content, and titratable acidity of organic, conventional, and integrated apples at harvest in 1999 and after storage at 1°C in regular or controlled atmosphere for three months Parameter (units)
Conventional
Integrated
70.6 a 13.3 a 0.76 b
Harvest z 68.5 b 13.2 a 0.81 a
65.4 c 13.4 a 0.74 b
50.2 a 14.6 a 0.52 b
Regular atmospherez 48.0 b 14.6 a 0.58 a
49.0 ab 14.3 a 0.57 a
60.7 a 15.3 a 0.70 a
Controlled atmospherez 59.0 b 14.7 b 0.71 a
57.0 c 14.7 b 0.70 a
Firmness (N) Soluble solids (%) Acidity (% MAEx )
66.9 a 14.6 a 0.71 b
Harvest + 7 daysz 65.5 ab 14.0 b 0.74 a
64.8 b 14.6 a 0.75 a
Firmness (N) Soluble solids (%) Acidity (% MAEx )
Regular atmosphere + 7 daysz 48.1 a 48.3 a 47.8 a 14.7 a 15.0 a 14.7 a 0.47 b 0.50 a 0.51 a
Firmness (N) Soluble solids (%) Acidity (% MAEx ) Firmness (N) Soluble solids (%) Acidity (% MAEx ) Firmness (N) Soluble solids (%) Acidity (% MAEx )
Organic y
Controlled atmosphere + 7 daysz Firmness (N) 57.0 a 57.0 a 57.3 a Soluble solids (%) 15.6 a 15.0 b 15.2 ab Acidity (% MAEx ) 0.59 b 0.62 a 0.61 a z Day following harvest or removal from storage, or 7 days later at 20°C in air. y Mean separation within rows by protected LSD at the 5% level. x MAE = malic acid equivalents.
298
