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  • Author or Editor: Wayne F. Whitehead x
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The effect of in-row plant densities on gas exchange, chlorophyll content and leaf area index of okra (Abelmoschus esculentus (L.) Moench) was studied. The six in-row plant densities ranged from 8 cm to 48 cm (D1 - D6). On 11 and 27 July 1990, the photosynthetically active radiation (PAR), transpiration (E), net photosynthesis (Pn) and chlorophyll content (Chl) at top- and mid-canopy levels and leaf area index (LAI) were measured. Mid-canopy PAR was 86 ± 6% less than that of the top-canopy and E, Pn and Chl at mid-canopy were respectively 55, 90 and 10% lower than those of the top-canopy. The interaction of plant density with canopy position was significant for E and Pn. The highest E and Pn, (12.28 mmol m-2 s-1 and 22.01 μmol CO2 m-2 s-1, respectively) were recorded at the D5 top-canopy. In-contrast, the lowest E and Pn, (4.17 mmol m-2 s-l and 1.23 μmol CO2 m-2 s-1, respectively) at the D6 mid-canopy were recorded. The LAI also exhibited significant variation among plant densities with a range of 4.65 to 4.97 for D5 and D3, respectively. These results indicate that 40 cm in-row density was the most suited for gas exchange of okra.

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This study was conducted over 3 years for the purpose of determining how tomato yield, fruit number, and vegetative dry matter are affected by winter cover crop and recommended fertilizer N rates. The following winter-spring fertility treatments were applied using randomized complete-block design with four replications: 1) 0 N winter–0 N spring, 2) 0 N winter–90 kg N/ha spring, 3) 0 N winter–180 kg N/ha spring, 4) 0 N winter+abruzi rye–0 N spring, 5) 0 N winter+hairy vetch–0 N spring, and 6) 0 N winter+crimson clover–0 N spring. In Spring of 1996, 1997, and 1999 `Mountain Pride' tomatoes were transplanted in all plots. Total yield was compiled over 6 weeks, while seasonal fruit number and plant dry matter were measured at final harvest. In 1999, highest plant dry matter (350.5 g/plant) was produced by vetch and highest fruit number (36/plant) by 180 kg N/ha. Total yield were highest (85.8 Mg/ha) at 90 kg N/ha in 1996 and lowest (35.3 Mg/ha) for control during 1997. Organic nitrogen from hairy vetch and crimson clover affected plant dry weight, tomato number and yield comparable to those receiving synthetic N. Results over three years for this study indicate that legume cover crops can be an effective N fertilizer in supporting plant dry matter, fruit number and fruit yield of tomato.

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The purpose of this study was to evaluate the tillage method effects of N sources on gas exchange (GE) at the flowering, fruiting, and pre-senescence in tomato. Measurements of transpiration (E), stomatal conductance (gs), photosynthesis (Pn), and internal leaf CO2 concentration (Ci) were reported. The following fall/spring tillage and fertility treatments were applied: 1) fall-fallow/spring-moldboard, 2) fall-fallow/spring-moldboard + 90 kg·ha–1 N, 3) fall-moldboard + hairy vetch/spring-chisel, 4) fall-moldboard + hairy vetch/springchisel + 90 kg·ha–1 N, 5) fall-minimum till+hairy vetch/spring-chisel, and 6) fall-minimum till + hairy vetch/spring-chisel + 90 kg·ha–1 N. During the 2nd week of Apr. 1995, `Mountain Pride' tomato was transplanted in all plots. Maximum E (11.9 mmol·m–2·s–1), gs (1465.1 mmol·m–2·s–1), and Pn (22.23 μmolCO2/m2 per s) occurred at the fruiting and highest Ci (301.2 μL·L–1) at the flowering. Throughout the growing seaon, treatments 5 and 3 affected GE rates the most, while treatments 1 and 3 at flowering affected Ci the most. Results indicate that fall moldboard or minimum-till + hairy vetch/spring chisel had greatest influence on GE of tomato.

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Reduced tillage saves energy and safeguards soil against erosion. While it is widely used for these reasons in producing agronomic crops, it has yet to find acceptance in vegetable cultivation. The main obstacle is the lack of knowledge of the growth and developmental responses of intensively managed vegetable crops to reduced tillage operations. Therefore, this study was performed to determine the effect of different tillage levels on vegetative growth and flowering and fruiting of tomatoes. The following tillage treatments were applied in a randomized complete-block design to a field that was cover cropped with vetch during winter T2 produced maximum vegetative dry weight/plant: 1) fall mold-board + spring no-till (T1), 2) fall mold-board + spring chisel (T2), and 3) fall chisel + spring chisel (T3). The number of flowers/plant were highest in T1, followed by T2 and T3, respectively. There was a 14: 1 ratio between the number of flowers and fruit set. The number of fruit in T1 and T2 were similar, and significantly greater than in T3. The fruit weight of T1 was similar to T2 but significantly greater than T3.

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The purpose of this 3-year study was to compare organic and inorganic N sources for promoting gas exchange (GE) in tomato at fruiting. Measurements of transpiration (E), photosynthesis (Pn) and internal leaf CO2 concentration (Ci) are reported. The following winter–spring fertility treatments were applied using randomized complete block design with four replications: 1) 0 N winter–0 N spring, 2) 0 N winter–90 kg N/ha spring, 3) 0 N winter–180 kg N/ha spring, 4) 0 N winter+abruzi rye–0 N spring, 5) 0 N winter+hairy vetch–0 N spring, and 6) 0 N winter+crimson clover–0 N spring. In spring of 1996, 1997, and 1999, `Mountain Pride' tomatoes were transplanted in all plots. Maximum E (14.3 μmol·m–2·s–1), Pn (22.8 μmol CO2/m2 per s), and Ci (352.2 μL·L–1) occurred in 1997, 1996, and 1999, respectively. In general, E was affected mostly by treatments 2, 3, 5, and 6 and Pn by treatments 2 and 5, while treatments 1 and 4 affected Ci the most. Results indicate that N from both legumes and synthetic fertilizer enhanced GE of tomato similarly.

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Parwal [Trichosanthus dioica (Roxb.)] is a tropical perennial vine producing small fleshy fruits used as a vegetable. It bears male and female flowers on separate plants. During the summer of 1996, a field study was conducted to determine if male and female plants differed in their gas exchange behavior. Three leaves per plant replicated six times for each sex were tagged randomly at initiation of gas exchange measurements. Transpiration (E), stomatal conductance (gs), CO2 exchange rate (CER), and internal leaf CO2 concentration (Ci) were measured when the leaves were 6, 18, 36, 47, 71, and 81 days old. In general, the gas exchange values for both sexes were similar. The leaves of male plants attained highest E, gs, and CER at 18 days of age. In female plants, CER peaked at an early leaf age of 6 days, while the peaks for E and gs were reached 30 days later. The highest Ci for both sexes were observed in 47-day-old leaves. Eighty-four-day-old leaves were no longer actively exchanging gases.

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The purpose of this study was to compare the efficacy of winter cover cropping with legumes for replacing synthetic N fertilization in tomato production. The following winter/spring fertility treatments were applied: 1) 0 N winter/ 0 N spring, 2) 0 N winter/90 kg·ha-1 N spring, 3) 0 N winter/180 kg·ha-1 N spring, 4) 0 N winter+rye/0 N spring, 5) 0 N winter+hairy vetch/0 N spring, and 6) 0 N winter+crimson clover/0 N spring. In the spring of 1996, tomato cultivar `Mountain Pride' was planted in all plots. The effects of different treatments on plant dry weight and fresh fruit yields were determined. Tomato following legumes or supplied with 90 kg·ha-1 fertilizer N produced highest plant dry weight, while 0 N winter/0 N spring and 0 N winter+rye/0 N spring produced plants with least dry weights. Treatments differed in a similar fashion also for fresh fruit yields. The results suggested that winter legumes were at par with commercial N fertilizer in supplying needed inorganic N to the succeeding tomato crop soil.

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The goal of this study was to compare the effect of leguminous and non-leguminous cover crops alone or in mixture with fertilizer nitrogen rates on kernel weight, ear number, and yield of Bt sweet corn. The following fall-spring fertility treatments were applied using randomized complete-block design with three replications: 1) fall-0 N, fallow; spring-0 N, 2) fall-0 N, abruzzi rye; spring-0 N, 3) fall-0 N, hairy vetch; spring-0 N, 4) fall-0 N, abruzzi rye+hairy vetch; spring-0 N, 5) fall-0 N, fallow; spring-101 kg N/ha, 6) fall-0 N, abruzzi rye; spring-101 kg N/ha, 7) fall-0 N, hairy vetch; spring-101 kg N/ha, 8) fall-0 N, abruzzi rye+hairy vetch; spring-101 kg N/ha, 9) fall-0 N, fallow; spring-202 kg N/ha, 10) fall-0 N, abruzzi rye; spring-202 kg N/ha, 11) fall-0 N, hairy vetch; spring-202 kg N/ha, and 12) fall-0 N, abruzzi rye+hairy vetch; spring-202 kg N/ha. In Spring of 2005, `Attribute BSS0977' bi-color (BC) supersweet (sh2) corn seeds were field planted. Total unhusked ear yield and ear number were harvested 74 days after planting, while kernel weight was measured from three randomly chosen ears. Maximum kernel fresh weight (111.6 g/ear), ear number (101,773/ha) and total yield (17.3 Mg/ha) were produced by hairy vetch; spring-101 kg N/ha. Minimum kernel fresh weight (23.0 g/ear) and ear number (51,485/ha) were produced by fallow; spring-0 N, while minimum total yield (2.2 Mg/ha) was produced by abruzzi rye; spring-0 N. Results indicate that hairy vetch supplemented with N at 101 kg/ha is most effective in supporting kernel fresh weight, ear number and yield of this BCsh2 corn variety.

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During the 2004–05 growing season, a study was conducted to determine effect of cover crop, their mixture and fertilizer N rates on above ground biomass (AGB) yields, and Leaf Area Index (LAI) of Bt sweet corn. The following cover crop nitrogen fertility treatments were applied using randomized complete-block design with three replications: 1) fall-0 N, fallow; spring-0 N, 2) fall-0 N, abruzzi rye; spring-0 N, 3) fall-0 N, hairy vetch; spring-0 N, 4) fall-0 N, abruzzi rye+hairy vetch; spring-0 N, 5) fall-0 N, fallow; spring-101 kg N/ha, 6) fall-0 N, abruzzi rye; spring-101 kg N/ha, 7) fall-0 N, hairy vetch; spring-101 kg N/ha, 8) fall-0 N, abruzzi rye+hairy vetch; spring-101 kg N/ha, 9) fall-0 N, fallow; spring-202 kg N/ha, 10) fall-0 N, abruzzi rye; spring-202 kg N/ha, 11) fall-0 N, hairy vetch; spring-202 kg N/ha, and 12) fall-0 N, abruzzi rye+hairy vetch; spring-202 kg N/ha. In Spring 2005, `Attribute BSS0977' bi-color (BC) supersweet (sh2) corn seeds were field planted. AGB yields were collected during harvest week while LAI was recorded at tasseling (6/27), silking (7/8) and one week after harvest (7/25). Hairy vetch; spring-101 kg N/ha produced highest LAI at tasseling (2.18), silking (2.73), and one week after harvest (2.57). Lowest LAI at tasseling (1.12) and silking(1.60) were produced by abruzzi rye; spring-0 N with fallow; spring-0 N producing lowest LAI (1.40) one week after harvest. Maximum AGB fresh (40.5 Mg/ha) and dry weight (12.1 Mg/ha) yields were produced by hairy vetch; spring-101kg N/ha, while minimum AGB fresh (9.6 Mg/ha) and dry weight (3.6 Mg/ha) yields were produced by abruzzi rye; spring-0 N. Results imply LAI at each growth stage and AGB yields of this BCsh2 corn variety are best supported by hairy vetch supplemented with N at 101 kg/ha.

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The purpose of this study was to evaluate how leguminous and non-leguminous cover crops alone or in mixture with synthetic nitrogen rates affect aboveground biomass, fruit number, and yield of eggplant. The following fall–spring fertility treatments were applied using randomized complete-block design with three replications: 1) fall-0 N, fallow; spring-0 N; 2) fall-0 N, abruzzi rye; spring-0 N; 3) fall-0 N, hairy vetch; spring-0 N; 4) fall-0 N, abruzzi rye+hairy vetch; spring-0 N; 5) fall-0 N, fallow; spring-70 kg×ha–1 N; 6) fall-0 N, abruzzi rye; spring-70 kg×ha–1 N; 7) fall-0 N, hairy vetch; spring-70 kg×ha–1 N; 8) fall-0 N, abruzzi rye+hairy vetch; spring-70 kg×ha–1 Na; 9) fall-0 N, fallow; spring-140 kg×ha–1 N, 10) fall-0 N, abruzzi rye; spring-140 kg×ha–1 N; 11) fall-0 N, hairy vetch; spring-140 kg×ha–1 N; and 12) fall-0 N, abruzzi rye+hairy vetch; spring-140 kg×ha–1 N. In Spring 2004, `Megal' eggplant seedlings were transplanted. Total yield and fruit number were compiled over 7 weeks, while total vegetative dry matter was measured at final harvest. Maximum aboveground biomass (227.6 g/plant), total yield (28.7 Mg×ha–1) and fruit number (13/plant) were produced by fall-0 N, hairy vetch; spring-70 kg×ha–1 N. Minimum aboveground biomass (53.0 g/plant) was produced by fall-0 N, abruzzi rye; spring-0 N, while minimum total yield (7.8 Mg×ha–1) and fruit number (5/plant) were produced by fall-0 N, fallow; spring-0 N. Results imply that hairy vetch supplemented with N at 70 kg×ha–1 is most effective in supporting fruit number and yield of eggplant.

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