Orchard floor management practicies for improving soil quality and optimizing nitrogen uptake efficiency
This research seeks to evaluate soil quality (soil biological characteristics, in particular) and N uptake, utilization, and distribution under a range of alternative orchard floor management systems (AOFMS). Additionally, we will determine whether AOFMS alter uptake efficiency of fertilizer N and its recycling and distribution within the tree. Compost and mulch amendments increased structural diversity of organisms in the soil. Compost amendments increased soil pH, organic matter, P, and K in both research locations and Mg and Ca at one location. All tissues from trees grown in compost-amended soils had a lesser amout of nitrogen derived from fertilizer.
1. Evaluate the effect of alternative orchard floor management systems on soil quality with emphasis on soil biological characteristics
2. Determine if the AOFMS can alter the uptake efficiency of fertilizer N, its distribution, and recycling within the tree
3. Determine the feasibility of AOFMW in commercial orchards
4. Perform cost and return analysis for different AOFMS
5. Communicate the research findings at IFP workshops, grower meetings, annual professional meetings, and via grower, scientific, and web-based publications
Objective 1. Soil samples from both research sites are being assessed for the quantity and type of nematodes as an indicator of soil biological diversity. The activity of soil organisms was assessed by measuring soil respiration every 2 weeks during the 2003 growing season at the Lewis-Brown site. Except for immediately following cultivation, there were no significant differences between the respiration rates in cultivated and herbicide-treated plots. Compost- and bark-mulch amended plots had higher respiration rates than non-amended and hay-amended plots. Also at the Lewis-Brown site, roots were sampled in the compost and non-amended plots using soil cores and are being analyzed to determine rate of mychorrizal infection. Soil tests to determine physical and chemical changes were performed at both sites at harvest.
Objective 2. After harvest the orchards at both sites were destructively harvested. Trees were divided into fruit, leaves, first-year wood, older wood, spurs, and roots. The research team is in the process of sampling, drying, and grinding each of the components. When grinding is completed, samples will be sent for 15N analysis. Leaf and wood samples were collected during summer pruning and fruit were sampled during thinning.
Objective 3. Yield and trunk circumference did not differ across all treatments at the Lewis-Brown site. To determine if soil amendments or weed control affect root length density, roots were sampled once a month during the summer of 2003 in the compost and non-amended plots at the Lewis-Brown site using soil cores. The percent weed coverage was lowest in mulch-amended plots.
Objective 4. Costs of amendments, their application, and the time needed to maintain the research blocks continue to be recorded.
Objective 5. Water infiltration and soil respiration were demonstrated and discussed at the Mid-Columbia field day in Hood River during the summer of 2003. The effects of soil amendments on soil biological and physical properties were discussed during an orchard tour at an on-farm grower research site.
Impacts and Contributions/Outcomes
Through the addition of compost and, to a lesser degree, mulch to the tree row, orchardists in the western region have the potential to increase the organic matter and structural diversity of organisms in a range of soil types. Compost amendments may increase soil pH and nutrient (P, K, Mg and Ca) levels.