Weed Control in Southern Highbush Blueberry with S-metolachlor,Flumioxazin, and Hexazinone

Field studies were conducted in 2010, 2011, and 2012 at a commercial blueberry farm near Burgaw, NC to determine weed control and crop tolerance to S-metolachlor and flumioxazin alone or mixed with hexazinone. Herbicides were applied pre-budbreak and postharvest. Pre-budbreak applications consisted of hexazinone at 1.1 or 2.2 kg ai ha^?1, S-metolachlor at 1.4 or 2.8 kg ai ha^–1, and flumioxazin at 215 g ai ha^–1 alone and tank mixes of hexazinone or flumioxazin plus S-metolachlor. Additional treatments consisted of flumioxazin (215 g ha^–1), flumioxazin plus S-metolachlor (1.4 and 2.8 kg ha^–1), or hexazinone (1.1 kg ha^–1) plus S-metolachlor (1.4 and 2.8 kg ha^–1) applied pre-budbreak and followed by (fb) a postharvest application of flumioxazin (215 g ha^–1). Herbicide programs containing flumioxazin resulted in greater Maryland meadowbeauty control (73%) 5 to 6 weeks after treatment (WAT) than herbicide programs containing hexazinone at 1.1 or 2.2 kg ha^–1 (37% and 39%, respectively). Needleleaf rosette grass control remained ≥94% for all herbicide programs through 2 WAT. Hexazinone at 1.1 kg ha^–1 provided greater needleleaf rosette grass control (87%) than flumioxazin (71%) 5 to 6 WAT. Meadowbeauty and needleleaf rosette grass control by all herbicide programs was poor (≤39% and ≤57%, respectively) 16 to 18 WAT. Two weeks after post-harvest applications, herbicide programs receiving a post-harvest flumioxazin application had greater meadowbeauty and needleleaf rosette grass control (78% and 84%, respectively) than those programs without a post-harvest flumioxazin application (43% and 71%, respectively).     

A comparison of high- and low-volume spray techniques in the thinning of ‘Golden Delicious’ apples

A trial at the Grove Research Station, southern Tasmania in 1989-90 examined the thinning of mature ‘Golden Delicious’ apple trees. High-volume sprays were applied at 6,0001 ha^-1 as air blast or vertical boom using NAA at 10mg l^-1 4d after full bloom (AFB) and 18 d AFB. Carbaryl at 1,000 mg l^-1 and thiram at 1200 mg l^-1 were also applied as combined sprays, 30 and 38 d AFB. These high-volume sprays were compared with unsprayed controls and Micron and Micronair low volume sprayers at 200 and 1,1000 l ha^-1. The dosages of the low volume applications were equilibrated to apply the same rates of chemical per hectare as the high-volume sprays, and the timing was the same. All spray treatments reduced crop load to acceptable levels when compared with the overcropped controls. There were no consistent differences between treatments for number of fruit per cm² limb area except that the lowest volume Micron spray thinned significantly less than most other treatments. Considering the number of fruit per 100 blossom clusters the airblast spray was the only treatment to be significantly better than the Micron at 2001 ha^-1. These numbers were reflected in mean fruit weight with the control fruit being significantly lighter than any sprayed fruit. The air blast treatment produced significantly heavier fruit than all other treatments, apart from the other high volume treatment. Fruit size distribution (FSD) showed significant differences between the control and all the spray treatments. The airblast treatment produced significantly more fruit in the 80 mm or larger category than all treatments, apart from the vertical boom application. These preliminary results suggest that although low-volume sprays can thin apple trees, the use of ultra low volumes (ULV) should be explored using machines capable of controlled droplet application (CDA). This may ultimately lead to less chemical being applied per hectare.     

The effects of Apogee® on shoot growth,secondary flowering,fire blight,fruit quality,yield and return bloom in ‘Bartlett’ pear growing in California

Summary

Apogee^® sprays were applied to mature ‘Bartlett’ pear (Pyrus communis L.) trees as single or multiple sprays during the growing seasons of 1999 to 2003 at concentrations of 420 g ha^–1 (125 mg ^–1) or 840 g ha^–1 (250 mg^–1): both reduced vegetative shoot growth. Two sprays of 840 g ha^–1 applied 3–3.5 weeks apart were most effective and reduced shoot growth by approximately 40%. An application made 2 d after fall bloom was ineffective and led to more vegetative shoot growth. Single sprays of Apogee^® made within 9–28 d after full bloom (DAFB) were equally effective in reducing vegetative shoot growth. Bourse shoot growth was reduced 43% by 3 April, 2001 (8 DAFB) treatment of 840 g ha^–1 when bourse and vegetative shoots ranged from 2.5 to 7.5 cm in length. Subsequent single applications of 840 g ha^–1 Apogee^® (on April 12 or 23, 2001) did not reduce bourse shoot growth significantly. Vegetative shoot growth was also reduced by 12% (9 d after treatment) and by 38% (approximately one month after treatment) by 840 g ha^–1 Apogee^® applied on 3 April, 2001, (8 DAFB). In 2002, bourse shoot growth was controlled most effectively by split applications (840 + 420 g ha^–1 or 840 2 g ha^–1, 9 April and 24 May) and by 840 g ha^–1 Apogee^®, applied at 2.5 to 7.5 cm shoot growth (9 April). These split applications, as well as girdling, decreased shoot strikes in 2002, the year after treatment. Split applications of 840 g ha^–1 Apogee^® made in April to early May were most effective in controlling both vegetative and bourse shoot growth in most years, although single applications of Apogee^® were effective in some years. Subsequent flushes of shoots tended to be controlled by split applications with the second application timed to the emergence of new shoots. Apogee^® was not consistently effective in reducing the incidence of Type I or Type V secondary flowers in these trials. Single or multiple sprays of Apogee^® had no measurable or consistent effect on return bloom, fruit size or shape, firmness, percentage soluble solids, or yield per tree over the period of these experiments. Apogee^® appears to have promise as a shoot growth control agent in ‘Bartlett’ pear growing in California, USA, without deleterious effects.     

Effects of N and K on growth,herbage, oil yield and nutrient uptake patterns in rosemary (Rosmarinus officinalis L.) under semi-arid tropical conditions

Summary

Essential oil of rosemary (Rosmarinus officinalis L.) possesses good olfactory properties and is suitable for use in perfumes, soaps and fragrances. Field experiments were conducted over 2 years (2003-2005) in an area experiencing a semi-arid tropical climate, to study the influence of two N levels (150 or 300 kg N ha^–1 year^–1) and three K levels (41.5, 83.0 or 124.5 kg K ha^–1 year^–1), or no fertiliser, on the growth, herbage and oil yields and nutrient uptake patterns of rosemary. The results showed that application of 300 kg N ha^–1 year^–1 produced higher herbage and oil yields in rosemary, compared with 150 or 0 kg N ha^–1 year^–1. The application of 83.0 kg K ha^–1 year^–1 produced maximum herbage and oil yields, compared with 0 or 41.5 kg K ha^–1 year^–1. Total N and K uptake levels were increased significantly by the application of N and K. Nitrogen uptake increased by 85.2% and 137.7%, and K by 80.9% and 123.9%, respectively, with the application of 150 or 300 kg N ha^–1 compared to controls (no N). Similarly, N uptake increased by 96.1%, 130.2% and 113.6%, and K by 79%, 124.3% and 110.4%, respectively, with the application of 41.5, 83.0, or 124.5 kg K ha^–1 compared to controls (no K). Oil content and oil composition were not influenced by nitrogen or potassium levels.     

Weed management in onion using chemical,non-chemical,and manual methods

Summary

Weed management studies in onions grown from seedlings were conducted during 2006 and 2007 at the National Agricultural Research Centre, Islamabad, Pakistan. Applications of pendimethalin at 0.825 l a.i. ha^–1, or oxadiazon at 0.240 l a.i. ha^–1, 2 d after transplanting (DAT) seedlings were evaluated alone, and in combination with one manual weeding, for their effects on weed competition and bulb yields. Other weed control treatments included the application of rice straw mulch 2 weeks after transplanting (WAT) combined with one manual weeding at 9 WAT, or a newspaper and rice straw mulch applied 2 WAT. Compared to the weed-free situation, competition with weeds caused reductions in bulb yields of 62% and 68% during the first and second year, respectively. Polygonum plebejum, Amaranthus viridis, Cyperus rotundus, and Coronopus didymus were the dominant weeds recorded in the field. Mulching reduced weeds by 56 – 60% compared to the chemical weed treatments. Compared to the weed-free treatment (four manual weedings at monthly intervals), which is a traditional method to control weeds in onion, bulb yields increased significantly under the rice straw mulch or when treated with pendimethalin in combination with one manual weeding at 9 WAT. The latter two treatments, on average, resulted in the highest increases of 26 t ha^–1 and 24 t ha^–1 in bulb yields with net returns of US$ 1,522 ha^–1 and US$ 1,486 ha^–1, respectively over the non-treated control.     

Effect of split applications of oil cake on leaf nutrient contents,tree growth,and fruit quality in non-astringent persimmon trees

Oil cake, widely used as an organic source of nutrients in horticultural production in South Korea, is a by-product when oil is extracted from various oilseeds. Split applications of oil cake were supplied to evaluate their effects on tree growth and fruit production in organic, non-astringent persimmon (Diospyros × kaki Thunb.) trees in 2009 and in 2010. Treatments included a single annual application of oil cake at 150 kg N ha^?1 in April (single application), two applications in April and July (105 and 45 kg N ha^?1, respectively; two-split application), or three applications in April, June, and August (60, 45, and 45 kg N ha^?1, respectively; three-split application), as well as zero application of oil cake (control). All applications of oil cake significantly increased the amount of ground-cover vegetation compared to the control. The single and two-split applications increased soil organic matter (OM), K₂O, CaO, and MgO concentrations, and cation exchange capacity to a soil depth of 0–30 cm in 2010. Oil cake applications increased soil porosity in 2010, as well as overall chlorophyll (SPAD values) and macronutrient concentrations in leaves in 2009 and 2010. Single and two-split applications stimulated water-sprout development, reduced the light intensity inside the tree canopy, and increased fruit drop. Fruit yield was higher in the two-split [24.7 metric tonnes (MT) ha^?1] and three-split application trees (25.0 MT ha^?1) compared to zero application control trees (19.8 MT ha^?1) and single application trees (21.0 MT ha^?1) in 2010. A single application resulted in soft fruit and slow skin colouration during maturation. Total soluble solids contents were higher in the control and three-split application trees in both years. The three-split application in 2010 increased the estimated production income by approx. 21% compared to the zero application, and by approx. 33% compared to a single application of oil cake.     

Response of cornmint (Mentha arvensis L. f. piperascens Malinv. ex Holmes) to micronutrients

Summary

A field experiment was carried over two years (1999 and 2000) in the subtropical climate of north India in a mollisol, to study the response of cornmint (Mentha arvensis L. f. piperascens Malinv. ex Holmes, Lamiaceae) ‘Himalaya ’ to application of six micronutrients, namely, iron (Fe: 15, 30, 45 kg ha^–1) manganese (Mn: 10, 20, 30 kg ha^–1), zinc (5, 10, 15 kg ha^–1), copper (Cu: 2, 4, 6 kg ha^–1), boron (B: 1, 2, 3 kg ha^–1) and molybdenum (Mo: 0.05, 0.10, 0.20 kg ha^–1). Application of micronutrients significantly increased the essential oil yield of cornmint in comparison with the control. However, the response to individual applications of micronutrients was observed up to 15 kg Fe, 10 kg Mn, 10 kg Zn, 2 kg Cu, 2 kg B or 0.05 kg Mo ha^–1. Beyond these levels, the essential oil yield variations among the doses within each trace element were not statistically significant. Of these rates of application, 2 kg B produced the maximum essential oil yield (116.5 kg ha^–1). The percentage increases in the essential oil yield over the control were: 36.2 for 15 kg Fe, 47.3 for 10 kg Mn, 35.7 for 10 kg Zn, 23.9 for 2 kg Cu, 62.9 for 2 kg B and 33.4 for 0.05 kg Mo.     

Effects of source,rate, and frequency of N application on yield,marketable grades and rot incidence of sweet onion (Allium cepa L. cv. Granex-33)

In a field experiment in the 1988-89 season, fertilizer formulations of NH₄NO₃, Ca(NO₃)₂, NaNO₃, NaKNO₃, and KNO₃ as N sources were applied at 84 and 168 kg N ha^?1 to onion plots direct seeded in the fall. A second experiment in the 1990-91 season tested the same N sources, except KNO₃, at rates of 168 and 224 kg ha^?1. Application strategy involved both splitting the total amount of fertilizer over two periods of the growing season (October–December and January—April) and the application frequency. With medium and high application rates (168 and 224 kg ha^?1), NH₄NO₃, NaNO₃, and NaKNO₃, increased high-value jumbo and large onions (premium marketable grade). Increased premium grades was due to increased bulb size and weight. Only NH₄NO₃ and Ca (NO₃)₂ increased total onion weight when N rate was increased from 84 to 168 kg ha^?1. Less frequent applications of split amounts of 84 kg N ha^?1 reduced marketable weight in the 1988–89 season, but doubling the rate to 168 kg ha^?1 restored the higher yields. At 224 kg N ha^?1 in the 1990–91 season, differences in onion grades were more pronounced among the different N sources, and NH4 NO₃ was superior in producing jumbo and large size onions. High N rates (224 kg ha^?1) and more frequent applications of split portions also increased the weight of jumbo onions. Split applications, providing 33% of the total N in the first 12 weeks of the growth period plus three applications of 22% each in the second 12 week period, increased bulb size and maximized yield of premium marketable grades. Effect of N rate on onion rot was dependent on split methods of applying the N during early and late growth periods. However, reduction in onion rot by the split application strategy was dependent on N source. Bulb decay was highest with NH4NO₃ and least with Ca(NO₃)₂ and NaNO₃.     

Effects of the amount of water applied,method of irrigation,and rate of N-application,on herbage and oil yields,N-uptake,and water-use efficiency in patchouli [Pogostemon cablin (Blanco) Benth.] grown under semi-arid tropical conditions

Summary

A field experiment was conducted during 2008 and 2009 at Bangalore, India, to study the effect of the amount of irrigation water applied (20, 25, or 30 mm per irrigation), the method of irrigation (i.e., flat-bed, or broad-bed and furrow) and nitrogen level (0, 50, or 100 kg N ha^–1) on herbage and oil yields, nitrogen (N) uptake, and water-use efficiency of patchouli [Pogostemon cablin (Blanco) Benth.]. At the highest level of N (100 kg N ha^–1), the broad-bed and furrow method was better suited for irrigating patchouli compared with the flat-bed method of irrigation. The highest herbage yield was achieved following the application of 100 kg N ha^–1 and 30 mm water per irrigation. However, with 25 mm irrigation, the broad-bed and furrow method increased N uptake (45.7 kg ha^–1) significantly compared with the flat-bed method of irrigation (36.7 kg ha^–1). The broad-bed and furrow method of irrigation increased the water-use efficiency significantly compared with the flat-bed method of irrigation. The content and quality of patchouli oil were not influenced by the amount of irrigation water, the method of irrigation, or N-level.     

Parthenocarpic fruit production in loquat (Eriobotrya japonica Lindl.) by using gibberellic acid

This study evaluates the effect of gibberellic acid (GA₃) in inducing parthenocarpy in ‘Algerie’ loquat, as well as the optimum treatment conditions and associated techniques, hand thinning and ringing, to produce seedless fruit with high enough quality for fresh consumption. GA₃ applied in the course of the phenological growth stages 504–508 of the BBCH-scale produced seedless fruits, with the magnitude of the response depending on the concentration applied and number of treatments. Percentage of panicles bearing seedless fruitlets significantly increased with increasing GA₃ concentrations up to 100 mg l⁻¹ and significantly and positively correlated with the number of treatments applied. Trees treated three times with 100 mg l⁻¹ developed more than 90% of panicles bearing almost 7 seedless fruits per panicle, which were smaller in size, drier and slightly acid but similar in TSS concentration and skin colour than seeded fruits from untreated trees. Fruit thinning to 3 fruits per panicle did not increase seedless fruit size, but ringing performed at the onset of cell enlargement stage, growth stage 702 of the BBCH-scale, significantly increased fruit size by 12–15%, depending on the year. Trees treated three times with 100 mg l⁻¹ of GA₃ and ringed produced 26 kg, on average, of seeded fruit of suitable commercial quality.     

Herbage and oil yield of geranium influenced by irrigation,nitrogen and organic mulch grown on alfisol

Summary

Two field experiments during 1996-98 at Bangalore, India studied the effect of soil moisture regimes (0.3, 0.6 and 0.9 IW:CPE ratios) irrigation water cumulative pan evaporation (IW:CPE) ratios and three levels of nitrogen application (0,100 and 200 kg ha^–1). Another experiment investigated three irrigation levels (0.3, 0.6 and 0.9 IW:CPE ratios), two levels of nitrogen application (100 and 200 kg ha^–1) and organic mulch (0 and 5 t ha^–1) on oil content, herbage, oil yield and quality of geranium grown on alfisols. Soil moisture maintained at 0.6-0.9 IW:CPE ratios significantly increased both the herbage and oil yields of geranium. Application of 200 kg N ha^–1 gave maximum herbage and oil yield compared with those obtained from 0 and 100 kg N ha^–1. Organic mulch increased the oil yield of geranium. The concentration and quality of essential oil were not influenced either by soil moisture regime, N rates or organic mulch.     

Evaluating the effectiveness of different strategies for calcium application on the accumulation of calcium in apple (Malus × domestica Borkh. ‘Braeburn’) fruit

Summary

Orchards displaying calcium (Ca) deficiency are a common phenomenon worldwide, despite the presence of sufficient Ca in the soil and the plant. A 3-year trial was conducted between the 2007 – 2008 and 2009 – 2010 growing seasons to evaluate the contributions of soil and foliar Ca applications to Ca concentrations in ‘Braeburn’ apple (Malus × domestica Borkh.) fruit. Ca(NO₃)₂ (Calflo; Yara Africa, Fourways North, South Africa) was applied as six separate foliar sprays until run-off. Applications were made at 1-week intervals between approx. 21 – 70 d after full bloom (DAFB) at 6.75 ml l^–1. Soil applications of Ca (Tropicote^TM; International ASA, Oslo, Norway) at 300 kg ha^–1 were applied at fruit set, or after harvest, according to standard practice. Mineral analysis was conducted to assess the soluble Ca concentrations of whole fruit (without pips and stalks), to quantify the contribution of foliar sprays or soil-applied Ca. Fruit Ca concentrations were maintained at satisfactory levels (4.5 mg Ca 100 g^–1 FW) at harvest by applying a series of six foliar sprays early in the season (for all seasons) during the trial period. Fruit Ca concentrations at 80 DAFB were highest in the treatments with foliar applications of Ca. In 2009 – 2010, Ca concentrations in apple fruit were lowest (8.38 mg 100 g^–1 FW) for soil application of Ca at fruit set. Ca applications to soil after harvest in the previous season, and soil applications shortly after fruit set in the current season, did not significantly increase Ca concentrations in current-season fruit, providing soil Ca levels were above the minimum requirement for apple trees. A possible explanation is that apple trees regulate their uptake of Ca through the roots when soil Ca is available in sufficient quantities. This confirms the importance of active root growth for efficient Ca uptake by apple trees when applying Ca to the soil.     

Seed Biology of the Weed Maryland Meadowbeauty (Rhexia mariana L.) in Blueberry (Vaccinium spp.)

Studies were conducted at three locations across the North Carolina coastal plain region to determine sexual reproductive potential, seedbank density, frequency of seed dormancy, and effect of temperature on Maryland meadowbeauty seed germination. Seed capsule density ranged from 500 per m² to 1124 per m² across locations. Each capsule contained an average of 74 seeds. Seeds germinated only in the 35/20 °C temperature regime, which represents the hottest month (August) of the growing season in southeastern North Carolina. Total number of germinated seeds differed across locations and ranged from 30% to 57%. The percent (average) of viable (66) and nonviable (26) meadowbeauty seeds was not different across locations. Relative germination and seed dormancy percentages were calculated based on the number of viable seeds. The percent relative germination and seed dormancy were different across locations and ranged from 47% to 86% and 14% to 55%, respectively. The highest number of germination resulted from 90 days of stratification. On average, 27 seeds germinated among soil samples, which is equivalent to 989 seeds per m². The data indicate that the populations of meadowbeauty in blueberry fields have the potential to sexually reproduce and contribute 5 × 10⁶ to 1.1 × 10⁷ seed capsules/ha and 3.7 × 10⁸ to 8.3 × 10⁸ seeds/ha of infestation. Freshly mature seeds can germinate and contribute 1.79 × 10⁸ to 7.14 × 10⁸ seedlings/ha in the year the seeds are produced and 5.18 × 10⁷ to 4.4 × 10⁸ seeds/ha can be dormant and incorporated into the seed bank on an annual basis. Approximately 9.89 × 10⁶ seeds/ha are dormant and viable in the soil and have the potential to germinate following adequate stratification.     

The effect of combined Azospirillum inoculation and nitrogen fertilizer on plant growth promotion and yield response of the blanket flower Gaillardia pulchella

The investigation was carried out to examine the performance of Azospirillum isolates on growth and N uptake of Gaillardia pulchella with two nitrogen levels. Azospirillum strain OAD-2 inoculation significantly increased plant height, number of leaves per plant, branches per plant and total dry mass accumulation in G. pulchella than other inoculations and/or uninoculated control. The application of 150 kg N ha⁻¹ further enhanced the above plant growth parameters significantly over application of 112 kg N ha⁻¹. The N uptake of G. pulchella was enhanced due to Azospirillum strain OAD-2 inoculation, which was further augmented in the presence of nitrogen. The combination of Azospirillum strain OAD-2 and 150 kg N ha⁻¹ showed the highest N uptake at 120 DAT. Plant growth and yield parameters also increased when inoculated with the non-diazotrophic, but efficient IAA producing, Azospirillum strain OAD-57. From this investigation, it can be concluded that Azospirillum strains OAD-2 and OAD-11 can play an important role in the N nutrition of G. pulchella.     

Determination of the uptake and translocation of nitrogen applied at different growth stages of a melon crop (Cucumis melo L.) using N isotope

In order to establish a rational nitrogen (N) fertilisation and reduce groundwater contamination, a clearer understanding of the N distribution through the growing season and its dynamics inside the plant is crucial. In two successive years, a melon crop (Cucumis melo L. cv. Sancho) was grown under field conditions to determine the uptake of N fertiliser, applied by means of fertigation at different stages of plant growth, and to follow the translocation of N in the plant using ¹⁵N-labelled N. In 2006, two experiments were carried out. In the first experiment, labelled ¹⁵N fertiliser was supplied at the female-bloom stage and in the second, at the end of fruit ripening. Labelled ¹⁵N fertiliser was made from ¹⁵NH₄¹⁵NO₃ (10 at.% ¹⁵N) and 9.6 kg N ha⁻¹ were applied in each experiment over 6 days (1.6 kg N ha⁻¹ d⁻¹). In 2007, the ¹⁵N treatment consisted of applying 20.4 kg N ha⁻¹ as ¹⁵NH₄¹⁵NO₃ (10 at.% ¹⁵N) in the middle of fruit growth, over 6 days (3.4 kg N ha⁻¹ d⁻¹). In addition, 93 and 95 kg N ha⁻¹ were supplied daily by fertigation as ammonium nitrate in 2006 and 2007, respectively. The results obtained in 2006 suggest that the uptake of N derived from labelled fertiliser by the above-ground parts of the plants was not affected by the time of fertiliser application. At the female-flowering and fruit-ripening stages, the N content derived from ¹⁵N-labelled fertiliser was close to 0.435 g m⁻² (about 45% of the N applied), while in the middle of fruit growth it was 1.45 g m⁻² (71% of the N applied). The N application time affected the amount of N derived from labelled fertiliser that was translocated to the fruits. When the N was supplied later, the N translocation was lower, ranging between 54% at female flowering and 32% at the end of fruit ripening. Approximately 85% of the N translocated came from the leaf when the N was applied at female flowering or in the middle of fruit growth. This value decreased to 72% when the ¹⁵N application was at the end of fruit ripening. The ammonium nitrate became available to the plant between 2 and 2.5 weeks after its application. Although the leaf N uptake varied during the crop cycle, the N absorption rate in the whole plant was linear, suggesting that the melon crop could be fertilised with constant daily N amounts until 2–3 weeks before the last harvest.     

1-Naphthaleneacetic acid and 6-benzyladenine thinning of a common slender spindle ‘Jonagold’/M.9 apple orchard. II: Partial tree spraying

Summary

Mature slender spindle ‘Jonagold’/M.9 apple (Malus × domestica Borkh.) trees were thinned using 10 mg l^–1 1-naphthaleneacetic acid (NAA) or 100 mg l^?1 6-benzyladenine (BA) and an axial fan sprayer at a spray volume of 1,500 l ha^?1 applied to the whole canopy, or with smaller volumes, where only the upper half of each canopy was sprayed. Partial spray applications of NAA or BA (at 1,000 l ha^?1, 750 l ha^?1, or 500 l ha^?1) to the upper half of the trees did not cause any reduction in final fruit numbers on the upper half, or on the lower half of each tree. When the whole tree was sprayed to run-off with the same thinning agent, or at 1,500 l ha^?1, successful thinning on both the upper and lower parts of the canopy occurred. Good spray coverage (from 51% to 77%) was also observed on leaves at all canopy positions measured, when whole trees were sprayed at 1,500 l ha^?1.The development of an innovative crop load regulation strategy was an objective of the ISAFRUIT Smartfruit Project.     

Effect of Anaerobic Soil Disinfestation and Mustard Seed Meal for Control of Charcoal Rot in California Strawberries

ABSTRACT

Anaerobic soil disinfestation (ASD) and mustard seed meal (MSM) appear to be promising non-fumigant alternatives for soilborne pathogens control. However, studies of their effect on charcoal rot caused by Macrophomina phaseolina in California strawberry are limited. A demonstration field trial with ASD with rice bran 20 t ha^–1 (ASD-RB), MSM 4.5 t ha^–1 (MSM), and ASD with rice bran 6.7 t ha^–1 + MSM 4.5 t ha^–1 (ASD-RB+MSM) treatments was conducted in a M. phaseolina-infested organic field in Oxnard, CA. A doubling of fruit yields relative to the grower standard, and a reduction in plant mortality by M. phaseolina, was achieved by ASD-RB. MSM failed to control M. phaseolina and resulted in fruit yields that were more than 20% below the ASD-RB yield. Fruit yield in the ASD-RB+MSM plot was intermediate between ASD-RB and MSM. Treatment effects on soil pH, EC, inorganic N dynamics, and soil microbial communities were also examined.     

Effects of nitrate,ammonium and chloride application on the yield and nitrate content of soil-grown lettuce

Summary

The effect of nitrogen availability and nitrogen form on the yield and nitrate content of butterhead lettuce (Lactuca sativa var. capitata L.) grown in soil under greenhouse conditions was studied. The extent to which chloride application can reduce nitrate content by supplying the plant with an alternative osmotically active anion, and whether the presence of ammonium in the soil is a necessary prerequisite for an effect of chloride, was also examined. Reducing NO₃-N availability from 260 to 200 kg N ha^–1 significantly reduced nitrate content while head fresh weight was unaffected. Further reducing NO₃-N availability to 120 kg N ha^–1 significantly reduced both nitrate content and fresh weight. Substituting 40% of the available NO₃-N with NH₄-N significantly reduced nitrate content while fresh weight was unaffected. The effect of NH₄-N application on plant nitrate content was enhanced by the application of the nitrification inhibitor dicyandiamide (DCD). Despite increasing chloride uptake, the application of chloride had no significant effect on head fresh weight or nitrate content when available nitrogen was in the nitrate form irrespective of the level of nitrogen application. Chloride application similarly had no effect on head fresh weight or nitrate content when applied together with ammonium without the nitrification inhibitor DCD, despite a greater uptake of chloride. Where both ammonium and DCD were applied, however, chloride application significantly reduced head nitrate content.     

Nutrient uptake of pepino plants in soilless cultivation

Summary

This study addresses vegetative growth and the uptake of nutrients and their accumulation in the vegetative and reproductive tissues of pepino (Solanum muricatum Ait.). The study was conducted in soilless plastic house conditions, with a planting density equivalent to 25.000 plants ha^–1 during two seasons (1997–98 and 1998–99). The plants were sampled, fractionated into leaves, stems, fruits and roots, then dried and weighed and the macronutrient content was analysed every 30.d for 300.d after transplanting. The yield obtained was 2.kg of fruit per plant, which is 30% of the total dry weight. The relative growth rate (RGR) ranged from 0.0028 to 0.0451.d^–1. The highest N, K, Ca and Mg concentrations were recorded in the leaves, and the highest P concentration in the roots. The nutrient accumulation of this yield was 10.64, 1.12, 16.06, 10.0 and 1.58.g of N, P, K, Ca and Mg per plant respectively. The highest accumulation of all nutrients was found in the leaves. The nutrient with the highest specificuptake rate was K, which ranged from 0.0037 to 0.0838.g g^–1 d^–1.     

Mechanische Fruchtbehangsregulierung

The objective of the present study was to thin apple flowers without use of chemicals, in order to improve fruit quality, reduce labour for hand thinning and overcome alternate bearing. The newly developed device comprises three rotors with adjustable angles and vertically rotating ropes, which remove excess apple flowers. Eleven year-old cv. ‘Braeburn’ apple trees were thinned at flower opening (BBCH growth stage 61) with the new device in Klein-Altendorf near Bonn, Germany. Adjacent untreated, hand-thinned or chemically (benzyladenine-)thinned apple trees of the same rows served as controls. Tree branches remained un-damaged by the vertically rotating ropes. Slight leaf damages of less than 8% were observed at the fastest rotor speed of 320?rpm, which also gave the best thinning results. The portion of class one fruits >?70?mm was increased by 10% without yield loss and by up to 20% with yield losses of ca. 5–10%, depending on the settings, relative to the untreated control. This was equivalent to fruit mass gains of 10?g without yield loss and of 20?g with 10%–20% yield loss with economic gain in both cases. The single or double-sided mechanical thinning required 1.2?h ha^?1 or 2.4?h ha^?1 at a tractor speed of 2.5?km h^?1 and reduced the subsequent hand thinning by respectively 20% or 45% (by 7?h or by 15?h/ha or its cost by 50–135 €/ha). The new device gently removed up to one third of both peripheral and central flowers at a cost of less than 100 €/ha and with a negligible risk of over-thinning and without effect on return bloom.