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Handell Larco, Bernadine C. Strik, David R. Bryla and Dan M. Sullivan

A systems trial was established in Oct. 2006 to evaluate management practices for organic production of northern highbush blueberry (Vaccinium corymbosum 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−1 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. Bed type affected most leaf nutrients measured in one or both cultivars during the first year after planting, including N, phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), boron (B), manganese (Mn), and zinc (Zn), but had less of an effect on leaf nutrients and no effect on soil pH, organic matter, or soil nutrients measured the next year. Feather meal contained 12 times more Ca and seven times more B than fish emulsion and resulted in higher levels of soil Ca and soil and leaf B in both cultivars, whereas fish emulsion contained three times more P, 100 times more K, and 60 times more copper (Cu) and resulted in higher levels of soil P, K, and Cu as well as a higher level of leaf P and K. Fish emulsion also reduced soil pH. Compost + sawdust mulch increased soil pH and organic matter and resulted in higher levels of soil nitrate-N (NO3-N), P, K, Ca, B, Cu, and Zn than sawdust alone and increased leaf K and B. Weed mat, in contrast, resulted in the lowest soil pH and increased soil ammonium-N (NH4-N). Weed mat also reduced soil Ca and Mg, but its effects on leaf nutrients were variable. Leaf Ca, Mg, and B were below levels recommended for blueberry the first year after planting when plants were fertilized with fish emulsion, whereas leaf N was low or deficient on average in the second year when plants were fertilized with feather meal. Leaf B was also low the second year in all treatments, and leaf Cu was marginally low. Leaf K, conversely, increased from the previous year and was becoming marginally high with fish emulsion. Fish emulsion, weed mat, and compost were generally the most favorable practices in terms of plant and soil nutrition. However, given the impact of each on soil pH and/or plant and soil K, further investigation is needed to determine whether these practices are sustainable over the long term for both conventional and organic production of highbush blueberry.

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Handell Larco, Bernadine C. Strik, David R. Bryla and Dan M. Sullivan

A systems trial was established in Oct. 2006 to evaluate management practices for organic production of northern highbush blueberry (Vaccinium corymbosum 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−1 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.

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James W. Julian, Bernadine C. Strik, Handell O. Larco, David R. Bryla and Dan M. Sullivan

A systems trial was established to evaluate factorial management practices for organic production of northern highbush blueberry (Vaccinium corymbosum L.). The practices included: flat and raised planting beds; feather meal and fish emulsion fertilizer applied at 29 and 57 kg·ha−1 of nitrogen (N); sawdust mulch, compost topped with sawdust mulch (compost + sawdust), or weed mat; and two cultivars, Duke and Liberty. The planting was established in Oct. 2006 and was certified organic in 2008. Weeds were managed by hand-hoeing or pulling in sawdust and weed mat-mulched plots and a combination of hand-pulling, propane-flaming, and post-emergent, targeted applications of acetic acid or lemon grass oil to any weeds present in the compost + sawdust plots depending on year. Data were recorded on input costs and returns in Year 0 (establishment year) through Year 3. Plants were harvested beginning the second year after planting. Planting costs were $741/ha higher on raised beds than on the flat, but the higher costs were more than offset by an average of 63% greater yields that improved net returns by as much as $2861/ha. Cumulative net returns after 3 years were negative and ranged from –$32,967 to –$50,352/ha when grown on raised beds and from –$34,320 to –$52,848/ha when grown on flat beds, depending on cultivar, mulch, and fertilizer rate and source. The greatest yields were obtained in plants fertilized with the low rate of fish emulsion or the high rate of feather meal, but fertilizing with fish emulsion by hand cost (materials and labor) as much as $5066/ha more than feather meal. Higher costs of establishment and pruning for ‘Liberty’ compared with ‘Duke’ were offset by higher net returns in all treatment combinations, except feather meal fertilizer with either weed mat or compost + sawdust mulch. Mulch type affected establishment costs, weed presence, and weed management costs, which included product and labor costs for application of herbicides (acetic acid and lemon grass oil) as well as labor for hand-weeding as needed, depending on the treatment. The highest yielding treatment combinations (growing on raised beds mulched with compost + sawdust and fertilized with fish emulsion) improved cumulative net returns as much as $19,333/ha over 3 years.