Three out of many pecan cultivars (Gloria, Pabst, & Stuart) were examined over long periods of time. The latter two cultivars have been planted since 1921 when the first pecan orchard was established. One tree of each of these cultivars were removed because of overcrowding. Gloria and Pabst were planted in 1954. Best production practices known were used until 1962. Fertilization and insecticide sprays were adopted. In 1970, spraying for disease was adopted. In 1974, drip irrigation and selective limb pruning were adopted. GrowSeason (GS) [(Year-Planted+l)-mean GS] was used in a linear (L), quadratic (Q), or cubic (C) model where the best model was chosen (significant F-test). Yield was expressed as cumulative yield. Older trees tended to produce more after 1962 (C trend), mid-aged trees more after 1970 (Q/C trend), and younger trees more after 1974 (L/Q trend). Younger trees had the greatest average yearly cumulative yield.
Yield and quality of pecan nuts were as high when 50 pounds N/acre was applied through a dripirrigation system as with 100 pounds/acre (112 kg·ha−1) applied either all broadcast or half broadcast-half fertigated. All N treatments kept leaf N well above the 2.50% (dry weight) lower threshold recommended for pecans. The 50 pounds N/acre-all-fertigated treatment resulted in less soil pH reduction and less loss of K, Ca, and Mg from soil in the nonwetted zone underneath the tree canopy than broadcast treatments. Soil pH, K, and Mg were slightly lowered in the 6- to 12-inch (15 to 30 cm) soil layer when all of the N was fertigated. Higher leaf Ca and Mg from the low rate of N fertigated reflected the higher concentrations of these elements in the soil in the nonwetted zone rather than the lower concentrations in the wetted zone. There was no evidence of a detrimental effect on the tree from lowering the N application to only 50 pounds/acre and applying it in four monthly applications through the drip irrigation system beginning 1 Apr.
The xylem water potential of leaves of peach [Prunus persica (L.) Batsch] was lower for trees with moderate to high counts of the phony peach disease organism in roots during the day in September and October (P = 0.1%), after bloom in March (P = 3%), and before harvest in May (P = 1%). No significant differences occurred for predawn measurements on any date, during periods of rapid shoot growth in June, and for measurements made on terminal twigs in January. Experimental results suggest that the phony disease organism invades and clogs the new xylem each year. The internal water stress that results when the tree transpires produces the fruit and shoot symptoms known as phony disease of peach.
Bahiagrass (Paspalum notatum Flugge cv. Paraguayan-22) growing under newly planted peach [Prunus persica (L.) Batsch.] trees severely stunted the trees. Neither supplemental fertilizer nor irrigating with two 3.8-liters·hour-1 emitters per tree eliminated tree stunting emitters were controlled by an automatic tensiometer set to maintain 3 kpa at a depth of 0.5 m under a tree in bahiagrass. Preplant fumigation with ethylene dibromide at 100 liters·ha-1 increased tree growth, but not tree survival. Fenamiphos, a nematicide, applied under the trees each spring and fall at a rate of 11 kg-ha -1 had no positive effect on tree survival, tree growth, or nematode populations. Bahiagrass tended to suppress populations of Meloidogyne spp. under the trees., Meloidogyne spp. were the only nematodes present that had mean populations > 65 per 150 cm3 of soil. Leaf concentrations of several elements differed between trees growing in bahiagrass sod and in. bare ground treated with herbicides. Leaf Ca was low for all treatments in spite of a soil pH near 6.5 and adequate soil Ca. The severe stunting of trees grown in bahiagrass, irrespective of the other treatments, demonstrated that bahiagrass should not be grown under newly planted trees. The low populations of parasitic nematodes in bahiagrass showed that bahiagrass has potential as a preplant biological control of nematodes harmful to peach trees. Chemical name used: ethyl 3-methy1-4-(methylthio) phenyl (1-methylethyl) phosphoramidate (fenamiphos).
Six tomato cultivars [Hotset, Petra, Stella, Big-O, Tropic, & Monte Carlo (fresh market)] were grown in a greenhouse in 1979 from July through November in 3 experiments. Exp. 1: The first two cultivars were used in a 15 cm, 30 cm, or 45 cm in-row spacing with rows spaced 60 cm apart. Cumulative fruit number and weight per unit area declined with increasing in-row spacing. Exp. 2: The first four cultivars were subjected to either cold or no cold treatment during germination before transplanting. No differences were found between the two treatments for mean fruit weight or total fruit number. Exp. 3: The last two cultivars were subjected to both the cold treatment and flower vibration. Cumulative fruit weight was greater for vibrated flowers. Greater mean fruit weight occurred earlier with cold treatment and declined significantly later in season, and was more pronounced in Tropic than Monte Carlo.
Two peach cultivars (Flordaking & Junegold) were planted in wheel-spoke design under a center pivot irrigation system. Main plots were sprays (Blast, Cheek, & Piggy-back) and cultivars. Sub-plots were training systems (Inside, Outside, & Standard). Sub-sub-plots were tree areas. Four rows were planted with two Inside rows and two Outside rows. Middle two rows of the standard plots were harvested. Intra-row spacing increased the further they were from the center. All trees harvested in 1990, standard plots were harvested every year, and Inside/Outside were harvested in alternate years. Most sources of variation in the model failed to be homogeneous among the 3 years. Since the number of trees harvested each year varied, all mean comparisons were done using the unequal N - unequal variance t-test.
Ten tomato cultivars (fresh market) were grown in a greenhouse using 30 cm or 45 cm in-row spacing with rows spaced 60 cm apart in 1979 from January through June. The cultivars were Big-O, Bigset, Hotset, Monte Carlo, Petra, Stella, Supal, Tropic, Wilters Villmarie, and WW200. Cultivars producing high number of fruit had lower fruit weight. Seven cultivars produced more fruit under the 30 cm spacing. Six cultivars produced slightly heavier fruit at 45 cm spacing and five cultivars produced larger class sized fruit at 45 cm spacing. Five cultivars had fruit by cluster distribution significantly higher up the plant at 45 cm spacing, while two were significantly lower. Three cultivars had greater production later in the growing period at 45 cm spacing, while two were greater at the beginning.
Observations in controlled field experiments over 5 years indicated that imidacloprid, applied as a soil drench around the trunks of peach (Prunus persica), nectarine (P. persica var. nectarine) and japanese plum (P. salicinia) trees at planting and in the early spring and mid-summer for two subsequent seasons (0.7 g/tree a.i.), slowed the development of symptoms of phony peach disease (PPD) and plum leaf scald (PLS) (Xylella fastidiosa) in the trees. After 3.5 years, the percentage of peach trees showing PPD symptoms was 8.5% for the imidacloprid-treated trees compared to 34.3% for untreated trees. After 4.5 years, the percentage of peach trees showing PPD symptoms was 13.1% in the treated trees and 71.4% in the untreated trees. After 3.5 years, nectarine trees in untreated and treated plots showed PPD symptoms in 8.3% and 0.9% of the trees, respectively. After 4.5 years, PPD symptoms in nectarine were found in 32.3% of the untreated trees and 8.5% of the treated trees. Development of PLS disease in plum was also slowed by the trunk drench with imidacloprid in two japanese plum varieties. After 3.5 years, dieback was observed in 55% of the twigs of untreated and 23% of the twigs of treated trees of `Au Rosa' plum and 33% of the twigs of untreated and 12% of the twigs of treated trees of `Santa Rosa' plum.