Nutrient Assimilation in Southern Highbush Blueberry and Implications for the Field

Abstract

<jats:p>Successful blueberry (<jats:italic>Vaccinium</jats:italic> sp.) cultivation typically requires soils with low pH, high organic matter, readily available iron, and nitrogen (N) in the ammonium form. Growth of blueberry on typical mineral soils (higher pH, low organic matter) is reduced. Although soil pH effects on nutrient availability and uptake are known, it is unclear if the requirement for low soil pH in blueberry production is due to effects on nutrient availability/uptake or is a more direct effect of rhizosphere pH on root function. In addition, it is unclear if the requirement for high organic matter (soil amendments) is related directly to nutrient availability/uptake. Several studies have examined the use of rootstocks to increase soil adaptation of blueberry and some of these rootstocks have been found to increase plant vigor and yield. In particular, we have investigated whether sparkleberry (<jats:italic>Vaccinium arboreum</jats:italic>)—a wild blueberry species that is adapted to high pH and low organic matter soils—could be used as a rootstock for commercial production of blueberry on mineral soils. Our work indicates that both nitrate (NO<jats:sub>3</jats:sub><jats:sup>−</jats:sup>) and iron (Fe) uptake and assimilation are greater in sparkleberry compared with southern highbush blueberry [SHB (<jats:italic>Vaccinium corymbosum</jats:italic> interspecific hybrid)]. This is correlated with increased activity of nitrate reductase (NR) and iron chelate reductase, the rate limiting enzymes for NO<jats:sub>3</jats:sub><jats:sup>−</jats:sup> and Fe acquisition, respectively. Field studies comparing growth and yield of own-rooted vs. grafted ‘Meadowlark’ and ‘Farthing’ SHB in amended vs. nonamended soils are ongoing. In general, own-rooted plants on amended soils exhibit greater growth than own-rooted on nonamended soils, while grafted plants in either soil system exhibit intermediate growth. Yields generally followed this pattern. Our preliminary results suggest that tolerance of SHB to mineral soils is greater when plants are grafted onto sparkleberry than when grown on their own roots. However, growth and yield of grafted plants grown under mineral soil conditions may not equal or exceed that of own-rooted plants grown under optimum soil conditions, at least in the first years after field planting. Longer term studies are necessary to fully evaluate the potential of using sparkleberry and other blueberry species as rootstocks for SHB and northern highbush blueberry (<jats:italic>V. corymbosum</jats:italic>).</jats:p>

Combined Effects of CaCO3 and the Proportion of N-NH4+ Among the Total Applied Inorganic N on the Growth and Mineral Uptake of Rabbiteye Blueberry

“…Several studies (e.g., Darnell and Hiss 2006;Darnell et al 2015;Nunez et al 2015;Poonnachit and Darnell 2004) have suggested that limitations on Fe uptake and/or Fe reduction inside the plant are the major obstacle to blueberry production under neutral and alkaline pH conditions. In the present study, no consistent effect of pH and the studied treatments on the Fe concentration in leaves was observed (Table 4) and, consequently, no significant relationship was found between biomass production and Fe concentration.…”

Vegetative and Physiological Responses of “Emerald” Blueberry to Ammoniacal Sources with a Nitrification Inhibitor

“…Tifblue, and by Claussen and Lenz (1999) on the genotype 13-16A, who also observed an early shoot growth detention and a premature senescence and leaf fall in blueberries fertilized with N-NO 3 − compared with NH 4 + . In addition, Darnell et al (2015) and Poonnachit and Darnell (2004) observed in blueberries "Sharpblue" and "Misty," respectively, a higher leaf, shoots and total dry biomass in plants treated with NH 4 + compared to those treated with NO 3 − . Nitrogen is the most important mineral for blueberry growth, and as for all crops, a slight or severe N deficiency may induce limitations in plant growth (Alt 2015).…”

“…In addition, some factors, as the pH of the soil, strongly determine the availability of NO 3 − and NH 4 + for plants. On one hand, NO 3 − is highly available in both acidic and alkaline soil conditions (Crisóstomo et al 2014;Darnell et al 2015). Otherwise, NH 4 + is mostly available at acid soil pH, because as the pH increases, it becomes more prone to volatilization and nitrification processes, which are closely determined by the activity of bacteria sensitive to temperature, O 2 availability, and soil acidity (Miller and Hawkins 2007).…”

“…Otherwise, the higher shoot growth and biomass production induced by N-NH 4 + may be related to the lower energy used by this N source to be metabolized within the plant cell since NH 4 + is directly incorporated into amino acids, whereas NO 3 − must first be reduced to NH 4 + by the activity of nitrate reductase (NR) and nitrite reductase (NiR) enzymes, whose activity requires energy (Hanson 2006;Martínez et al 2017). In addition, Darnell et al (2015) reported a low capacity of southern highbush blueberry to catalyze the reduction of NO 3 − to NO 2 − , and then to NH 4 + due to a reduced activity of NR and NiR enzymes in their tissues. In Significance p = 0.0009 p = 0.0275 p = 0.0054 p = 0.0231 n.s.…”

Comprehensive resistance evaluation of 15 blueberry cultivars under high soil pH stress based on growth phenotype and physiological traits

“…Currently, many studies on the use of morphological and physiological indicators for plant resistance evaluation and cultivar screening have been reported. According to related studies, several blueberry cultivars have varying levels of tolerance for high soil pH (Darnell et al, 2015). However, a comprehensive evaluation of the tolerance of different blueberry cultivars to high soil pH has not been reported.…”