Individual and Combined Use of Sawdust and Weed Mat Mulch in a New Planting of Northern Highbush Blueberry. II. Nutrient Uptake and Allocation

Abstract

A 2-year trial was established in Oct. 2016 in western Oregon to evaluate the effects of various in-row mulch treatments on establishment of northern highbush blueberry (Vaccinium corymbosum L. ‘Duke’). The treatments included douglas fir [Pseudotsuga menziesii (Mirb.) Franco] sawdust, black weed mat (woven polypropylene groundcover), green weed mat, and sawdust covered with black or green weed mat. For the most part, plant nutrient concentration and content were unaffected by the color of the weed mat. In both years, mulching with weed mat over sawdust reduced soil NO3-N compared with weed mat alone. The only other soil nutrient affected by mulch was K, which was highest with sawdust mulch and intermediate with black weed mat alone in year 2. There were inconsistent effects of mulch on leaf nutrient concentration during the study. In 2018, leaf N concentration was lowest with black weed mat over sawdust. There were few mulch effects on nutrient concentrations in senescent leaves in both years and in harvested fruit in year 2. Mulch had greater effect on nutrient concentration in dormant plant parts after the second growing season than after the first, with the addition of sawdust under weed mat leading to significant differences for many nutrients in various plant parts compared with weed mat alone. Total uptake of N ranged from 12 kg·ha−1 (black weed mat) to 17 kg·ha−1 (black weed mat over sawdust) in year 1 and averaged 33 kg·ha−1 in year 2, with no effect of mulch. Fertilizer use efficiency for N was 8% to 12% in year 1 and 42% in year 2. Uptake of other nutrients was unaffected by mulch and, depending on the year, ranged from 1.3 to 4.3 kg·ha−1 P, 4.0 to 8.0 kg·ha−1 K, 2.1 to 4.9 kg·ha−1 Ca, and 1.0 to 1.5 kg·ha−1 Mg. Each of these other nutrients was derived from the soil or decomposing roots.

Individual and Combined Use of Sawdust and Weed Mat Mulch in a New Planting of Northern Highbush Blueberry. III. Yield, Fruit Quality, and Costs

“…Strik et al (2017b) also found that weed mat over sawdust resulted in a higher yield for several cultivars compared with a compost and sawdust mulch, but they hypothesized that higher soil pH caused by the use of compost was detrimental to yield. In this study, the soil pH was unaffected by mulch from 2017 to 2018 (Strik et al, 2020b) or in subsequent years (average, 4.8; data not shown), and it remained within the recommended range of 4.5 to 5.5 for highbush blueberry (Hart et al, 2006). Contrasts showed that mulch color (black vs. green) had no impact on yield in 2018, whereas the addition of sawdust underneath weed mat increased the yield compared with weed mat alone or sawdust alone.…”

“…Mulch treatment had no significant effect on yield in 2019 or 2020, or on cumulative yield during the 3-year period. Black weed mat over sawdust did increase plant biomass and nutrient accumulation in 2018 compared with black alone (Strik et al, 2020a(Strik et al, , 2020b, likely resulting in the higher yield reported for that year. However, mulch had few consistent effects on soil and leaf nutrients or soil organic matter during the first 2 years of the study (Strik et al, 2020a(Strik et al, , 2020b or in 2019 and 2020 (data not shown), which may be related to the lack of significant differences in yield.…”

“…In contrast, Strik et al (2017a) found that black weed mat and sawdust mulches alone had no effect on TSS. Because weed mat color had no impact on soil or canopy temperature, plant growth, or nutrient allocation (Strik et al, 2020a(Strik et al, , 2020b, it is not surprising that contrasts consistently showed no effect of weed mat color on fruit quality. Previous studies of blueberry (Strik et al, 2017a(Strik et al, , 2017bTertuliano et al, 2012) and apple (Choi et al, 2011) also found little impact of mulch on these same fruit quality traits.…”

“…Plants were pruned each winter according to commercial grower practices. Further details regarding site preparation, planting establishment, and cultural management are provided in our companion work regarding mulch effects on soil and canopy temperature and plant biomass (Strik et al, 2020a) and on nutrient uptake (Strik et al, 2020b).…”

“…Plots of each treatment were arranged in a completely randomized block design with five replicates. At planting, each plot included a row of nine plants spaced 0.9 m apart that was separated from adjacent plots in the row by 3 m. Plants were removed to analyze the nutrient content and biomass as described by Strik et al (2020aStrik et al ( , 2020b, leaving eight plants per plot in 2018 and six plants per plot in 2019 and 2020. Rows were spaced 3 m apart.…”