+ ) forms are insoluble. Immobility of Fe at high soil pH (7.4–8.5) may be the main factor responsible for Fe and other micronutrient deficiency in vegetable crops ( Fisher et al., 2003 ; Schulte, 2004 ). As pH increases, Fe solubility decreases. At high pH
Kevin R. Kosola* and Rebecca L. Darnell
Cultivated Vaccinium species (e.g. highbush blueberry, Vaccinium corymbosum, or cranberry, V. macrocarpon) commonly require acidic soil (pH 4.5 to 5.5) for optimum growth. Under these conditions, ammonium (NH4 +) is the dominant form of inorganic N. In contrast, V. arboreum, the sparkleberry can tolerate higher-pH mineral soils, where nitrate (NO3 -) is typically the predominant inorganic N form. This tolerance may be related to increased ability to acquire and utilize NO3—N. Measurements of 15NO3 - and 15NH4 + influx kinetics in excised roots of V. arboreum, V. corymbosum, and V. macrocarpon did not support this hypothesis. NO3 - influx kinetics measured from 10 micromolar to 200 micromolar NO3 - were similar among all three species. NO3 - influx was consistently lower than NH4 + influx at all concentrations for all three species.
Shengrui Yao, Steve Guldan, Robert Flynn, and Carlos Ochoa
leaf sampling. To evaluate cultivar tolerance to high soil pH, leaf chlorosis was monitored. Leaf color was measured with a Minolta chlorophyll meter SPAD-502 (Spectrum Technologies, Aurora, IL) on 4 July, 30 July, and 3 Sept. 2011; 19 May and 5 Sept
Timothy K. Broschat
characterizes K-deficient leaves ( Broschat, 2005a ). Mn deficiency is usually caused by high soil pH, although transient, cold temperature-induced Mn deficiency is fairly common in coconut palm in Florida ( Broschat and Donselman, 1985 ). The use of composted
David L. Creech
Blueberry growers are encouraged to monitor soil, leaf tissue, and irrigation water on a regular basis. Recommendations are based on soil, leaf, and water guidelines established from previous studies. A 1986-1988 blueberry field study in east Texas and Louisiana revealed the following significant associations with low vigor fields: 1) high soil pH, Ca, Mg and low Zn, 2) high leaf Na and B, and 3) high irrigation water conductivity and bicarbonates. The findings will be compared to other benchmark studies. pH, conductivity, and nutrient monitoring procedures of a large east Texas rabbiteye blueberry field are described. Careful record-keeping allows blueberry growers to fine-tune fertigation performance by altering nitrogen source and rate depending on changes in soil pH and conductivity.
L. Brandenberger, R. Wiedenfeld, R. Mercado, J. Lopez, and T.E. Morelock
Southern peas for the processing market are an important crop for producers in South Texas, but little testing of new varieties or breeding lines has been carried out. Grower field trials during three different years and an on station trial provided an opportunity to evaluate >30 different pea cultivars or breeding lines. Cultivars and breeding lines were evaluated for earliness, maturity, yield, and performance in high-pH soils. Yields varied significantly each season, with Arkansas Blackeye # 1 providing consistently high yields in the three grower trials. Both Arkansas 87-435-68 and Texas Pinkeye produced significantly higher yields in the high soil pH trial at Weslaco. Yields for Arkansas 87-435-68 and Texas Pinkeye in the Weslaco trial were 1428 and 1231 lb of dry peas per acre, respectively.
Chris Ramcharan and Paul Hepperly
Twelve cvs. of Papaya were evaluated for yield and tolerance to drought, high soil pH and disease incidence under a non-pesticide low-input system. Superior yields were obtained from Barbados Solo (BDX 584-1) - 67.1 Kg/tree (tr) and 987 g/fruit (fr), Guanica (GU 2-1) - 60.7 Kg/tr and 888 g/fr, PR 6-65 × Cariflora (CF) - 46.6 Kg/tr and 700 g/fr, and CF - 48.5 Kg/tr and 607 g/fr. Most cvs. survived 19 months with peak yields at 15 months. Pencil top was major disease and only the Palau cv. exhibited St. Croix decline symptoms. Vigorous cvs. included GU 2-1, CF, PR 6-65 × CF and Criolla (CR) several plants of which are fruiting 26 months after planting. Chlorophyll data indicated that CF and CR cvs. had best tolerance to high pH conditions. Cvs. with large pulp size included GU 2-1 (3.7 cm) and SRS × CF (4.2). Brix analyses indicated sweetest fruits were from CF (14.2), SRS × CF (13.4), GU 2-1 (13.7) and PR 6-65 × CF (12.9).
Chad E. Finn, James J. Luby, Carl J. Rosen, and Peter D. Ascher
Thirty-three seedling progenies from crosses among Vaccinium corymbosum L., V. angustifolium Ait., and V. corymbosum/V. angustifolium hybrid-derivative parents, and `Northblue', `Northsky', and `Northcountry' were grown for 2 years at three soil pH levels at Becker, Minn. Iron sulfate and lime were incorporated to amend the soil to pH levels of 4.0 and 6.5, respectively; the native soil, pH 4.5, was the third pH regime. The plants grew well in the low pH regime, poorly in the high pH regime, and intermediately in the native pH regime. Variation among populations was significant for all traits except vitality 18 months after being planted, and pH treatment affected all traits. The pH regime × population interactions were not significant for any of the plant performance characteristics. Nondestructive subjective and objective measurements were positively and highly correlated with total plant dry weight. Therefore, populations could be effectively evaluated for tolerance to higher pH without destroying the plant. Vaccinium angustifolium was not a general source of tolerance to higher pH, but some populations derived from V. angustifolium were tolerant of high soil pH.
Rodrigo Figueroa, Douglas Doohan, and John Cardina
Common groundsel (Senecio vulgaris) is an increasingly important weed in strawberries (Fragaria ×ananassa), a crop in which open space within and between rows is susceptible to infestations. Cultivation, hand hoeing, and registered herbicide are only partially effective in controlling common groundsel, and tolerance or resistance to herbicides is common in this species. Field and greenhouse studies were conducted to identify and select herbicides for controlling common groundsel in newly planted strawberries. Herbicides applied to strawberries within 1 week after planting in 2000 were: terbacil and simazine alone and tank mixed with napropamide; pendimethalin, dimethenamid, metolachlor, ethofumesate and sulfentrazone. Based on selectivity and efficacy observed in this preliminary experiment, sulfentrazone and flumiclorac were selected for further evaluation in 2001 and 2002. Strawberry tolerance of sulfentrazone and flumiclorac 1, 3, 6, and 18 weeks after application (WAA) was similar to that of the registered herbicides terbacil and napropamide, but injury was greater than in hand weeded plots. Plants sprayed with 300 g·ha–1 (4.3 oz/acre) sulfentrazone produced yields similar to terbacil treated plants, but with less plant stunting. Tolerance of newly planted `Allstar' and `Jewel' was affected by the interaction of soil pH and sulfentrazone rate. Plant stunting 3 WAA increased with sulfentrazone rate, reaching 68 and 61% in `Allstar' and `Jewel', respectively, with the highest rate [400 g·ha–1 (5.7 oz/acre)] and high soil pH (7). `Allstar' grown in low pH (5) and treated with sulfentrazone (400 g·ha–1) showed only 8% stunting, whereas `Jewel' was not stunted 3 WAA at the same rate and pH. Both cultivars recovered (50% less stunting) from the severe injury observed when sulfentrazone was applied to high pH soils. However, at low pH both cultivars were stunted more at 6 WAA than at 3 WAA. Plant diameter for both cultivars was 25% higher when they were grown in the lower soil pH. Fruit yield was not affected by the sulfentrazone rates evaluated (0 to 400 g·ha–1). Sulfentrazone was active at four stages of common groundsel growth: preemergence (PRE), cotyledon (COT), early post (EPOST) seedlings at the four-leaf stage, and late post (LPOST) seedlings at the10-leaf stage. The calculated 50% growth reduction (GR50) value for PRE and COT stages was 50 g·ha–1 (0.7 oz/acre), whereas the GR50 for EPOST and LPOST stages was 100 g·ha–1 (1.4 oz/acre). Sulfentrazone controlled common groundsel when applied PRE and COT, but at EPOST and LPOST stages sulfentrazone did not provide complete control, although plant height was reduced 80% to 90% compared to untreated plants. Results indicated that common groundsel is controlled in the field with 150 and 300 g·ha–1 (2.1 and 4.3 oz/acre) of sulfentrazone applied before seedling emergence. The least strawberry injury occurred when sulfentrazone was applied immediately after transplanting at 150 and 300 g·ha–1, although crop tolerance was reduced under conditions of high soil pH (>6.5) and varied with cultivar.
Joan R. Davenport and Carolyn DeMoranville
Native nitrogen is released when soils are mineralized. The amount of N released by this process depends on the amount of organic matter present and soil temperature. Cranberry (Vaccinium macrocarpon Ait.) grows in acidic soils with a wide range in organic matter content. To evaluate release of cranberry soil N at varied soil temperatures, intact soils were collected from sites that had received no fertilizer. Soils were cored and placed in polyvinyl chloride (PVC) columns 20 cm deep × 5 cm in diameter. Four different soil types, representing the array of conditions in cranberry soil (mineral, sanded organic, organic peat, and muck) were used. Additional columns of sand soil (pH 4.5) that had been pH adjusted to high (6.5) and low (3.0) were also prepared. Each column was incubated sequentially at six different temperatures from 10 to 24 °C (2.8 °C temperature intervals) for 3 weeks at each temperature, with the soils leached twice weekly to determine the amount of N release. The total amount of N in leachate was highest in the organic soils, intermediate in the sanded organic, and lowest in the sands. At the lowest temperature (10 °C), higher amounts of N were released in sanded organic and sand than in organic soils. This was attributed to a flush of mineralization with change in the aerobic status and initial soil warming. The degree of decomposition in the organic soils was important in determining which form of N predominated in the leachate. In the more highly decomposed soil (muck), most of the N was converted to nitrate. In the pH adjusted sand, high soil pH (6.5) resulted in an increase in nitrate in the leachate but no change in ammonium when compared to non-adjusted (pH 4.5) and acidified (pH 3.0) treatments. This study suggests that for cranberry soils with organic matter content of at least 1.5% little to no soil-applied fertilizer N is needed early in the season, until soil temperatures reach 13 °C. This temperature is consistent with the beginning of active nutrient uptake by roots. Soil N release from native organic matter was fairly consistent until soil temperatures exceeded 21 °C, indicating that when temperatures exceed 21 °C, planned fertilizer applications should be reduced, particularly in highly organic soils.