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United States Department of Agriculture

Agricultural Research Service

Research Project: Long-Term Impact of Nitrogen Fertilizer Rate, Sawdust Mulch, and Pre-Plant Amendment on Yield, Fruit Quality, and Soil Microbiology in Blueberry

Location: Horticultural Crops Research

2013 Annual Report


1a.Objectives (from AD-416):
Determine the long-term impact of pre-plant incorporation of sawdust and surface sawdust mulch and nitrogen fertilizer rate on yield, fruit size, fruit firmness, soil nutrient status, soil properties, and soil microbiology in a well established planting of Elliott.


1b.Approach (from AD-416):
We established a new planting of ‘Elliott’ blueberry at the North Willamette Research and Extension Center (NWREC) in October, 2003 on a site not previously planted to blueberries. The soil pH prior to planting was 5.4. At the end of the study, representative plants per plot will be removed and divided into their various components to assess treatment effects on nutrient status, partitioning, with nutrient budgeting done per acre. Data will be presented on all variables measured by year and cumulative yield with impacts of sawdust incorporation at planting, mulching, and N rate on soil biology and yield and quality parameters.


3.Progress Report:

This research was conduction in support of NP 305 objective 1 "Determine nutrient requirements to enhance product quality in woody perennial crops such as grapevine and rhododendron" of the parent project. Plots with sawdust incorporated had a decreased level of soil moisture and required 5-6 times more irrigation water during the growing season than un-incorporated plots. Overall, early plant growth, yield, and soil moisture were adversely affected by pre-plant incorporation of sawdust in a Willamette silt loam soil. There has been no significant effect of N fertilization rate on cumulative yield. While cumulative yield has not been affected by incorporation of sawdust or mulch alone, there was a significant interaction between mulch and incorporation; plots in which sawdust had been incorporated before planting had a higher cumulative yield if no mulch was used.

Nitrogen fertilization with the high rate of N has decreased fruit size, including cumulative average fruit weight. There has been no treatment effect on firmness. However, there is a trend for fertilization with the high rate of N to increase firmness, likely because smaller fruit (as found in the high fertilization rate treatment) are firmer. Treatments had no effect of percent moisture content of fruit, which averaged about 82%. Leaf P, K, Mg, S, Fe, and Zn were not affected by N fertilization rate and did not have concentrations below recommended standards. Work is on-going on the impact of treatments on plant and soil nutrient status, soil microbiology, and plant and soil carbon allocation.


Last Modified: 10/25/2014
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