Field plots on Norfolk sandy loam soil at Tuskegee and Eufaula, AL were treated by soil solarization (SS). Samples rhizsosphere (R) and nonrhizosphere soil from cole crop and strawberry plots were collected and assayed with selective media for population densities of microbes involved in organic decomposition and mineralization. Microflora population densities of bacteria, actinomycetes and fungi increased 2-7 folds in the solarized compared to the bare soil (BS). Microflora population densities in the soils involved in cellulose and protein decomposition, ammonification, nitrification, phosphate mineralization were greater in solarized soil compared to BS. Nitrogen-fixing bacteria in R soil 7 months after SS was higher when compared to BS at Tuskegee, but was reduced 50 folds 18 months after SS.
C. Stevens, V. A. Khan, A. Y. Tang and R. M. Cody
Harry S. Agamalian
Initial weed competition in newly planted grapevines can delay vine development, resulting in reduced first harvest. The experiments were conducted over a three year period on three wine grape varieties: Chardonnay, Semillon, and Napa Gamay.
Dormant rooted plants were winter planted and subjected to soil applied preemergence herbicides. The experiment was conducted on a Greenfield sandy loam under sprinkler irrigation. Major weeds were little mallow (Malva pariflora), hairy nightshade (Solanum sarachoides), lambsquarters (Chenopodium album), and Russian thistle (Sasola iberica).
Vine growth was evaluated on cane weights, cane diameter, and cane length. Weed interference over the three year period resulted in 50% reduction in vine growth the first year. Yield data obtained from the third year resulted in significant differences between the weed free vines compared to the non-weeded treatments.
D. G. Mortley, J. Y. Lu, P. Grant and G. W. Carver
The effect of periodic removal of peanut foliage for use as a green vegetable on final foliage and nut production was evaluated in a field experiment in the summer of 1992. Georgia Red peanut cultivar was grown in Norfolk sandy loam soil in a randomized complete block design with four replications. Treatments consisted of removing peanut foliage at 2, 4, and 6 weeks, starting six weeks after planting, and an untreated check. Fresh foliage yield declined an average of 30% while dry weight declined 34% when harvested at 2 and 4 weeks. Nut yield declined 33% when harvested at 2 and 4 weeks but yield decreased only 10% when harvested at 6 weeks. Peanut greens are highly nutritious especially as a rich source of vitamin C and protein. For good balance between foliage and nut production, it appears that harvest intervals should be after four weeks.
B.D. McCraw and M.W. Smith
Taproots of 2-year-old `Apache' seedling pecan [Carya illinoensis (Wang)] trees were pruned to 1 ft (30 cm), 2 ft (60 cm), or 3 ft (90 cm) in combination with wounding treatments consisting of no wounding, scraping through pericycle tissue on one or two sides of the taproot, or longitudinally splitting the taproot for about half its length. The trees were planted in a Port silt loam soil and a Teller sandy loam soil and grown without irrigation. At the end of the first and second growing seasons, top growth was measured, trees were dug and root system regrowth was evaluated. Tree root weight and number of roots per tree decreased with increasing taproot length.
P. D. Dukes, J. R. Bohac and J. D. Mueller
A root-knot nematode (Meloldogyne incognita) project was initiated in a field of infested sandy loam (EREC) in 1991 and continued. There were ten sweetpotato entries consisting of six cultivars (Beauregard. Excel, Georgia Jet, Jewel, Red Jewel, and Sumor), three advanced lines (W-270, W-274, and W-279) and PI 399161 which were selected for their diversity in disease reactions and other traits. Each entry was planted in the same plots each year to monitor effects of continuous cropping, disease reactions, yield and population shifts of the pathogen. Marketable yields were reduced each year for Georgia Jet and Red Jewel, but not for Beauregard. Internal necrosis in the storage roots was most severe for Beauregard. Several of the highly resistant entries, especially Sumor and W-279, performed well each year, including high yields, good quality. and little or no nematode reproduction. This study demonstrates the considerable economic benefits of a high level of durable resistance to root knot in sweetpotato.
H. E. Hohlt, H. P. Wilson and T. E. Hines
During 1989, clomazone (Command) was applied pretransplant or preemergence to transplanted and seeded watermelon (Citrullus lanatus, cv. Charleston Gray), respectively. Rates of 280, 414, and 560 g ai·ha-1 (0.50, 0.75, 1.0 pt/A) clomazone were applied to a Bojac sandy loam. Plots were rated for percentage weed control 21 DAT. Control of common lambsquarters [Chenopodium album (L.)], large crabgrass [Digitaria sanguinalis (L.) Scop.], and smooth pigweed (Amaranthus hybridus L.) increased with rate although smooth pigweed control was low. A significant phytotoxic injury characterized by bleaching and reduced growth occurred at all rates on melon transplants. No significant phytotoxicity occurred in seeded plots 35 DAT. Vine length (cm) was recorded 42 DAT. Vine length was reduced significantly at the 560 g·ha-1 rate in transplants. Vine length of seeded watermelons was not significantly affected.
R. A. Straw and C. A. Mullins
Tomato trials with black plastic mulch, drip irrigation, and fertigation were conducted on a Lily sandy loam soil of medium fertility at Crossville, TN in 1990 and 1991. 'Mountain Pride' tomatoes were fertilized with a broadcast preplant application of 1120 kg ha–1 of 10-4.4-8.3 fertilizer with and without combinations of black plastic mulch and weekly applications of 0.64 cm of water for 12 weeks through drip irrigation. Three black plastic mulch and drip irrigation treatments supplied additional nitrogen and potassium fertilizer through the drip irrigation system. Yields were increased by use of black plastic mulch and by trickle irrigation in 1991. However, additions of fertilizer through drip irrigation had no effect on yields.
W.B. Evans and D.D. Warncke
Single-plant microplots of `Russet Norkotah' potatoes (Solanum tuberosum L.) were grown outdoors in a 5 × 5 factorial RCBD of indigenous phosphorous level (200, 325, 450, 575, 700 kg·ha-1 Bray-Kurtz Pl extractable; McBride sandy loam) and banded triple super phosphate (0, 50, 100, 150, 200 kg P2O5/ha). Disease in the low P soil that was used to create the four lower P soil blends completely confounds response of the plants across indigenous P levels and might have accentuated responses within levels. Plants responded to fertilizer P with tuber yield increases of 100, 70, 40, and 10 percent within the 200, 325, 450, and 575 indigenous P levels, respectively. Fertilizer P also increased marketable yield and tuber P concentration. Neither indigenous nor fertilizer P altered tuber specific gravity.
Companion studies compare the responses of corn (Zea mays L.) and potato to indigenous soil P levels and quantify P uptake among potato cultivars in solution culture.
Susan D. Day and Nina L. Bassuk
Four techniques for compaction amelioration were studied: 1) Vertical drainage panels; 2) vertical gravel-filled sump drains; 3) soil trenches filled with sandy loam; and 4) peat amended back fill. The control was backfilled with existing soil on the site. Vertical drainage mats and vertical gravel-filled sump drains were shown to increase O2% in surrounding soil; however, all O2 levels regardless of treatment were above what is considered limiting. Shoot and root growth of Pyrus calleryana `Redspire' was greatest for treatments that alleviated mechanical impedance (soil trenches and amended back fill) and least for treatments that did not (controls and vertical drains). Vertical drainage mats which alleviated mechanical impedance to a lesser degree showed intermediate growth.
Mack A. Wilson and Michael Aide
Potatoes (Solantum tuberosum) were grown on a Lilbourn sandy loam entisol in Charleston, Missouri, with varying rates of potassium fertilizer. Four rates of murate of potash (KCl) were used; 0, 196, 392 and 582 Kg-K/HA. Potassium was measured in tuber and soil by atomic absorption spectrophotometry. The amount of soil potassium was apparently high. Although potassium content in the two cultivars of potatoes, `Norchip' and `Atlantis' was slightly higher (2.3-3.7) as compared to another researcher's data (2%). Obviously, the need for potassium fertilizer for vegetable crops is related to the supplying ability of the soil. Tuber yields (Kg/HA) were higher with added rates of potassium fertilizer than the control, and the results were significant. Yields (Kg/HA) of `Atlantis' were significantly higher than `Norchip.'