Mulch and Fertilizer Management Practices for Organic Production of Highbush Blueberry. I: Plant Growth and Allocation of Biomass during Establishment

Abstract

<jats:p>A systems trial was established in Oct. 2006 to evaluate management practices for organic production of northern highbush blueberry (<jats:italic>Vaccinium corymbosum</jats:italic> L.). The practices included: flat and raised planting beds; feather meal and fish emulsion fertilizer each applied at rates of 29 and 57 kg·ha<jats:sup>−1</jats:sup> nitrogen (N); sawdust mulch, compost topped with sawdust mulch (compost + sawdust), or weed mat; and two cultivars, Duke and Liberty. Each treatment was irrigated by drip and weeds were controlled as needed. The planting was certified organic in 2008. After one growing season, allocation of biomass to the roots was greater when plants were grown on raised beds than on flat beds, mulched with organic mulch rather than a weed mat, and fertilized with the lower rate of N. Plants also allocated more biomass belowground when fertilized with feather meal than with fish emulsion. Although fish emulsion improved growth relative to feather meal in the establishment year, this was not the case the next year when feather meal was applied earlier. After two seasons, total plant dry weight (DW) was generally greater on raised beds than on flat beds, but the difference varied depending on fertilizer and the type of mulch used. Shoots and leaves accounted for 60% to 77% of total plant biomass, whereas roots accounted for 7% to 19% and fruit accounted for 4% to 18%. Plants produced 33% higher yield when grown on raised beds than on flat beds and had 36% higher yield with weed mat than with sawdust mulch. Yield was also higher when plants were fertilized with the low rate of fish emulsion than with any other fertilizer treatment in ‘Duke’ but was unaffected by fertilizer source or rate in ‘Liberty’. Although raised beds and sawdust or sawdust + compost produced the largest total plant DW, the greatest shoot growth and yield occurred when plants were mulched with weed mat or compost + sawdust on raised beds in both cultivars. The impact of these organic production practices on root development may affect the sustainability of these production systems over time, however, because plants with lower root-to-shoot ratios may be more sensitive to cultural or environmental stresses.</jats:p>

Northern Highbush Blueberry Cultivars Differed in Yield and Fruit Quality in Two Organic Production Systems from Planting to Maturity

“…It is important to note that soil pH in the compost + sawdust treatment remained above the desirable range for blueberry (4.5-5.5; Hart et al, 2006), whereas it was within this range in the weed mat treatment throughout the study (Table 3). Larco et al (2013a) found lower soil pH under weed mat mulch than under a yard-debris compost + sawdust mulch in organic blueberry. However, use of a yard-debris compost only as part of a mulching program had benefits for mitigating the decline in soil pH that occurs with fertilization over time, while maintaining soil pH within the desired range for blueberry (Larco et al, 2013a;Strik, 2016).…”

“…It is possible that the cultivars differed in their adaptability to the various fertility regimes caused by the amendmentmulch treatments and fertilizers used in our study. Larco et al (2013aLarco et al ( , 2013b and Strik (2016) observed differences in plant growth and yield between 'Duke' and 'Liberty' when fertilized with fish emulsion or feather meal in a certified organic production system. Incorporation of a preplant amendment, particularly douglas fir sawdust in our region, is common (Julian et al, 2011a(Julian et al, , 2011b and has been shown to improve growth and production over the long-term compared with no preplant amendment in conventionally managed blueberry fields (Nemeth et al, 2017).…”

“…The soil at the site is a Willamette silt loam (fine-silty mixed superactive mesic Pachic Ultic Argixeroll) and had a pH of 4.9 and 3.7% OM. Details on preplant site preparation can be found in Larco et al (2013a).…”

“…The development of yield and fruit quality of the range of cultivars grown has not been compared in research studies, likely because of the relatively long time from planting to maturity (about 8 years). Differences in the performance of cultivars have been found in organic production of 'Duke' and 'Liberty' blueberry (Larco et al, 2013a(Larco et al, , 2013bStrik, 2016;Strik et al, 2016) and various blackberry cultivars (Fernandez-Salvador et al, 2015).…”

Applied Manure and Nutrient Chemistry for Sustainable Agriculture and Environment

“…Results from a recent study on organic blueberry indicated that a 4-cm deep layer of yard debris compost covered with 5 cm of sawdust mulch produced more shoot growth and higher early yields than 9 cm of sawdust alone but reduced net cumulative returns relative to weed mat (landscape fabric) or sawdust alone by as much as $7,800/ha, primarily due to higher weed management costs (Julian et al 2012;Larco et al 2013a). We consider composts with total K > 10 g/kg, total cations > 1.5 mol (+)/ kg, compost acidification requirement to pH 5 (as determined by pH buffering capacity test) > 0.5 mol H + per kg, and EC > 4 dS/m (by SME) to be a risk for short-term plant damage when applied at high rates (>5 cm depth of compost applied to the beds).…”