An increase in the K level in orange and grapefruit trees generally increases the thickness of the peel and reduces the percentage of juice in the fruit. Data presented in this report show that an increase in K in the lemon tree has the opposite effect as that which occurs in the orange and grapefruit tree. An increase in the level in lemon trees resulted in thinner peels and in a higher percentage of juice in the fruit.
High-value crops (tobacco and sweet corn) often receive high levels of N fertilizer during the growing season rather than risk yield and/or quality reductions. Following harvest, small-grain winter cover crops are sown to reduce soil erosion and recover residual fertilizer N. Fall cole crops, such as cabbage, grow rapidly in early fall, respond well to N fertilization, and have the potential to be sold for supplemental income. The objectives of this study were to 1) compare fall cabbage and winter rye as scavengers of residual fertilizer N and 2) determine if a relationship between fall soil mineral-N (NO–3 +) levels and fall cabbage yield response to N fertilization exists. Soil mineral N levels following sweet corn and tobacco ranged from 22 to 53 mg·kg–1 in the surface 30-cm and declined with depth. Fall cabbage appeared to be as effective as rye at reducing soil mineral N levels. No fall cabbage dry matter yield response to applied N was measured in 1993 and 1995. However, following sweet corn in 1994, a small cabbage yield response to N at 56 kg·ha–1 was measured when the soil mineral level, prior to fall fertilization, was 22 mg·kg–1.
By far the most important subtropical fruit is citrus and the most widely grown citrus is the sweet orange. Lemon and grapefruit also are important citrus species. Other important subtropical fruits are dates, figs, and olives. Tropical fruits are most numerous in kinds, and a few, such as the avocado, litchi and mango are grown on a commercial scale in the subtropical regions. Others, such as bananas, pineapples, coffee, and papaya, are strictly tropical. It is not an uncommon practice to apply K, but it is done in many cases without a demonstrated need. With the realization of the broad effects of K, such a practice should not be followed, but K level should be adjusted to give optimum response for both quality and yield. For this diagnostic methods and standards are required.
During 1975 and the spring of 1976, N requirements were determined for irrigated ‘Walter’ tomatoes (Lycopersicon esculentum Mill.) growing on Troup loamy sand with and without polyethylene mulch. Maximum soil moisture deviation occurred in the unmulched plots in the zone of illuviation to depths of 60 to 75 cm. Moisture ranged from 3 to 15% with the maximum recorded after vines were killed by frost. Highest N concentration (15.8 ppm NO3-N) occurred in mulched plots at a depth of 15 cm; whereas the highest concentration (11.5 ppm NO3-N) in unmulched plots occurred at 45 cm. The highest yield of 29.8 MT/ha was produced with 60 kg/ha N on mulched plots. The highest yield without mulch (25.6 MT/ha) required 138 kg/ha of N.
Kentucky is one of seven states in the southeast evaluating 13 Asian pear cultivars for suitability to the region. The cultivars were planted on a (20′ × 10′) spacing in 1989 at three separate locations. Data on time of bloom, tree growth, fire blight susceptibility and fruit quality and yield were collected. This study demonstrates the variability seen in Asian pear cultivars in response to site. There was a significant site by cultivar interaction for fire blight. The Princeton site had significantly more fire blight than either Lexington or Quicksand. Four cultivars, Niitaka, Shin Li, Shinko and Shinseiki had low fire blight ratings which were not significantly different between the three sites. Asian pear growth rates were significantly different between the three sites, but cultivar growth rates were not. Tree growth rate showed a significant negative correlation to fire blight rating. That is infected trees did not grow much. Initial findings show Shinko, Shinseiki and Niitaka to have some tolerance to fire blight spread and to produce good yields of attractive fruit. However, Niitaka had a very tough skin with a tendency towards fruit cracking. The cultivar Shin Li which also had fire blight tolerance did not produce fruit or flowers.
Four different netting types were evaluated in the field for excluding Japanese beetles and green June beetles from `Dirksen' thornless blackberry plants. These nets were bird net, crop net, rack mesh, and Agryl P17. Observations were made in an unreplicated trial on `Reliance' grapes using OV3018 and OV7100 nets in addition to those listed. Plants were not sprayed with insecticides or fungicides after net application. Rack mesh appears to be the best net of those evaluated during a dry season for excluding Japanese beetles and green June beetles on thornless blackberries and grapes. Plants covered with rack mesh had minimal fruit and foliage damage due to insects and fruit rot. The use of rack mesh eliminated the need for insecticide sprays for 53 days on thornless blackberries and 41 days on grapes. Light intensity was reduced by the netting, but did not reduce (hornless blackberry yield or soluble solids; however it did unacceptably reduce `Reliance' grape fruit coloration.
Field experiments in the past on Valencia orange trees in California have not shown any clear K deficiency as indicated by the effects of K applications on numbers of fruit produced per tree. Such experiments were established with little knowledge of the initial K nutritional status of the trees in question. Commercial use of citrus leaf analysis as a diagnostic tool has increased in recent years, and through this medium an orchard was found near Escondido, California with leaf K levels which indicated possible K deficiency. Some of the initial results of an experiment in this orchard are given in Table 1.
Starch in the roots of mandarin trees (Citrus reticulata Blanco cv. Kinnow) was drastically reduced by an “on” crop. This was related to prolonged bud dormancy, delayed spring growth and an “off’ crop the following year.
Apple growers would like to use pesticides efficiently and diminish concerns about food safety and pesticide usage. The 1992 Apple IPM Program objectives were: 1) to demonstrate the application of Integrated Pest Management practices in commercial orchards and, 2) to provide the training and support needed to help these growers become self sufficient in IPM practices. Grower training meetings and regular scouting of the orchards were the primary educational methods. End-of-the-season evaluations of past and disease incidence were made. Except for Frogeye Leaf Spot, there were no significant differences in insect pest, disease levels or in fruit quality attributes in IPM versus standard blocks. The IPM blocks had significantly more mite incidence. Growers did produce commercially acceptable crops using IPM based decisions while reducing the average past control cost by $56 par acre. Educational programs did help growers to be more proficient in making IPM based decisions.
Twelve shrub rose cultivars were evaluated for pest resistance in the southern Blue Ridge mountains under high humidity and rainfall (1.34 inches per week average during the 1994 and 1995 growing seasons). `Albo plena', `Blanc Double de Coubert', `Fru Dagmar Hastrup', `Roseraie de l'Hay', R. rugosa `Alba', `Sarah van Fleet', and `Topaz Jewel' were highly resistant to black spot and Cercospora sp. leaf spot. `Alba Meidiland', `Linda Campbell', `Pink Meidiland', and `Scarlet Meidiland' were susceptible, while `Bonica' displayed intermediate resistance to both diseases. `Sarah van Fleet' foliage and the flowers of `Albo plena', `Blanc Double de Coubert', and R. rugosa `Alba' were damaged by Japanese beetle feeding. No other cultivars were damaged by Japanese beetles.