Orchard floor management practicies for improving soil quality and optimizing nitrogen uptake efficiency
The research funded by this grant seeks to evaluate soil quality and N uptake, utilization and distribution under a range of alternative orchard floor management systems (AOFMS). The major objectives are to determine the effect of AOFMS on soil biological characteristics, in particular. Additionally, we hope to answer the question of whether AOFMS will alter uptake efficiency of fertilizer N, and its recycling and distribution within the tree. Crop profitability and feasibility analysis will accompany the biological data analysis. Finds will be communicated at participatory and traditional grower workshops and field days, and in grower and scientific publications.
Component sampling began in January 2002 following the first season of 15N fertilizer application. Wood of various ages, spurs and root samples were collected. Soil samples were taken in October to analyze differences from initial baseline physical and chemical characteristics in 2000 to 2002. Data were obtained from two experiment station research plots: Lewis-Brown (8-yr old ‘Fuji’ apple trees) and Hood River (3-yr old ‘Red Delicious’). Tree row amendment treatments; no amendment, legume/grain hay, compost and bark mulch were re-applied in the fall to those two research plots and one on-farm observation plot, adding only enough amendment to maintain a 3-4 inch layer. The additional treatment of herbicide or cultivation across the tree row amendments continued with three separate cultivation events needed to keep the weeds at bay. Enriched 15N was applied to single-tree replicates at the research plots.
Nematode species were extracted and are being identified from soil samples taken from each plot in fall 2002. Preliminary soil respiration measurements were taken at both research sites and will continue to be sampled in 2003. Fruit and leaf samples were collected for 15N analysis. Tissues continue to be prepared and sent for analysis. Yield and trunk circumference were obtained. Vole trapping took place fall 2002. Percent weed coverage was determined at the end of the growing season.
Mid-Columbia Agricultural Research & Extension Center (MCAREC) Annual Field Day was an opportunity to show the effects of AOFMSs on water infiltration and begin to introduce soil respiration elements of this research. In November a poster of this research was presented at the Northwest Symposium on Organic and BioIntensive Farming: advances in research and education conference.
Grower cooperators were interviewed again this year after the growing season. They observed an uneven ripening and delay in harvest with compost amendments. Concerns were raised over scion-rooting in the compost and bark mulch amendments.
1. To evaluate the effect of alternative orchard floor management systems (AOFMS) on soil quality with emphasis on soil biological characteristics.
2. Determine if the AOFMS can improve the uptake efficiency of fertilizer N, its distribution and recycling within the tree.
3.To determine feasibility of AOFMS in commercial orchards (determine the effect on pest populations, tree growth, yield and fruit quality).
4.Perform crop profitability analyses for different AOFMS’s.
5. Communicate the research findings at Integrated Fruit Production workshops, grower meetings, annual professional meetings and via grower, scientific and web-based publications.
Under objective 1. Soil samples from both research sites are currently being quantitatively and qualitatively assessed for nematodes. Soil respiration measurements began in late summer. Soil tests for physical and chemical changes were obtained. Compost treated plots, whether cultivated or herbicide sprayed for weed control, had significantly higher levels of organic matter, calcium, potassium, phosphorus, magnesium and sodium. At both sites the cation exchange capacity did not differ between treatments, however, pH was significantly higher in the compost plots (Table 1 in printed copy).
Under objective 2. Component (various ages of wood, spurs and roots) samples were collected in January 2002, leaf samples in August and fruit samples at thinning events and harvest. Samples have been dried, ground and we are currently waiting for results from 15N analysis.
Under objective 3. Fruit quality was assessed on a packing line for the ‘Red Delicious’ apples from the MCAREC plots. Although there were no differences in the breakout of Washington extra fancy, extra fancy and fancy categories, mulch and compost amended plots had the highest percent culls by weight. In spring and late fall of 2002 traps were set out for voles. No voles were trapped, however, several deer mice, predominately in the compost areas, were tagged. Percent weed cover was lowest in mulch-amended plots at both research sites. There was no significant difference in yield efficiency between treatments.
Under objective 4. Costs for amendments, their application and the amount of time needed to maintain the research blocks continue to be recorded.
Under objective 5. Water infiltration was demonstrated and soil respiration was discussed during the MCAREC Annual Field Day tour in Hood River this summer. A poster was presented at the NY Symposium on Organic and BioIntensive Farming conference in Yakima, Washington.
A timeline in Figure 1 (in printed copy) shows the progression of research at both sites during 2002.
Impacts and Contributions/Outcomes
The ‘Fuji’ apples, which are biennial bearing, showed a significantly higher yield in compost-treated plots. The foliage was more vibrant in color and a significantly higher amount of prunings were removed from compost plots indicating increased vigor. In Hood River, the ‘Red Delicious’ trees are much younger and yields are still too small to make a statistical comparison.