Orchard floor management practicies for improving soil quality and optimizing nitrogen uptake efficiency
The research evaluates soil quality and N uptake, utilization and distribution under a range of alternative orchard floor management systems (AOFMS). Crop profitability and feasibility analysis accompany the biological data analysis. Field studies began spring 2001 when tree row amendments (no amendment, legume/grain hay, compost, and bark mulch) were applied. Rows were cultivated or received an herbicide treatment. Enriched 15N was applied to single-tree replicates. Active fungal and bacterial biomass, and protozoa were measured fall 2001. Leaf, fruit, wood and root N samples are being analyzed. A participatory soil quality workshop was offered. Three field tours highlighted the research goals.
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.
Two replicated research trials were established, one at the Lewis-Brown farm in Corvallis, OR in an 8-yr old ‘Fuji’ block and one at the Mid-Columbia Research and Extension Center in Hood River, OR in a 3-yr old ‘Red Delicious’ block. Tree row amendments were applied in March and April to the two experiment station farms and three on-farm trials. A split-plot design was employed at the research farms where the main plots received either cultivation or herbicide treatments. The sub-plots consisted of four tree row amendments: no amendment, grain/legume hay, compost and mulch. 15N-enriched ammonium sulfate was applied to single-tree replicates at each experiment station planting.
Under objective 1. Baseline physical and chemical soil characteristics were obtained at the experiment station plots. In the fall, active fungal and bacterial biomass after a year of treatment was quantified. Cultivation or herbicide treatments had no significant effect on soil biota. At the Hood River planting, no amendment plots had the highest active bacterial biomass while the hay plots were the lowest. Compost plots had the highest active fungal biomass while mulch treatments were the lowest. However, there were no statistical differences in the ratio of fungal to bacterial biomass. In Lewis-Brown, there were no significant main effects. The interaction term between the main plots and the sub-plots were significant for active fungal biomass and the ratio of fungal to bacterial biomass.
Under objective 2. Leaf (mid-shoot and spur) samples were collected in the summer. After harvest, fruit samples were also collected. Leaf samples were again collected in the fall and a variety of wood and root samples were also gathered after the growing season.
Under objective 3. Vole trapping was begun in fall. The weed coverage within the tree row was determined and weed species were characterized. Tree growth was measured (trunk circumference) and fruit yields were obtained from the experiment station plots. Compost treatments at the Lewis-Brown farm produced more vigorous trees. ‘Fuji’ trees bore few to no fruit and the ‘Red Delicious’ trees produced their first light crop therefore no quality analysis was done in fall 2001.
Under objective 4. Costs for amendments, their application and the amount of time needed to maintain the research blocks have been recorded.
Under objective 5. A soil quality workshop was held on 8 March for the Mid-Columbia orchardists of Oregon. New tools were developed for illustrating soil quality concepts. Three summer tours highlighted the research plots.
Impacts and Contributions/Outcomes
It is too early in the research process to determine impacts and contributions.