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The objective of this study was to identify a sweetpotato canopy type ideally suited to suppress weed growth. With this knowledge, breeders could select sweetpotatoes that require less weed control. Diverse canopy types, ranging from upright, short-internode bunch types to long-internode trailing types, were compared in a split-plot design (hand-weeded and weed treatments). We also included lines with deeply lobed leaves (palmate) and more entire-leaf types. Our results show no significant differences between lines for total ground surface area covered after 6 weeks of growth, no differences in weed dry weight at harvest and few differences in canopy dry weight at harvest. Total ground surface area covered correlated positively with total yield, and weed dry weight correlated negatively to total yield. We were unable to identify individual lines that yield better when pressured with weeds compared to the hand-weeded control, but we were able to identify lines that yield poorly when pressured with weeds compared to the hand-weeded control. These results demonstrate the difficulty in categorically identifying a superior canopy.
Abstract
Greenhouse-grown peach [Prunus persica (L.) Batsch] seedlings and cuttings were drought-stressed by reducing soil water potential (ψsoil) from field capacity (FC) to permanent wilting point, (PWP). Mean ψsoil and leaf water potential (ψleaf) were correlated with measurements of stomatal conductance (gs), net photosynthetic (Pn) rate, and vapor pressure deficit (VPD). Decreasing Pn and gs trends were noted as ψsoil decreased. Photosynthetic rate and gs were significantly reduced at ψleaf more negative than −1.5 MPa. Values of Pn and gs were more highly correlated to ψleaf than ψsoil. A midday depression in Pn rates began 2 hr earlier and peak rates were at least 50% lower when ψsoil was more negative than −0.05 MPa. The correlation coefficient (r) between ψleaf and ψsoil and between gs and Pn rate at different ψsoil was above 0.70. The r values decreased as soil and plant water potential became more negative. Stomatal conductance peaked at optimal ψsoil (FC) 2 hr following sunrise. Photosynthetic rate peaked at a ψsoil around −0.05 MPa 4 hr after sunrise.
Five years of testing found equal damage on peaches from trees sprayed with an air-blast sprayer or with a PASS. A PASS is a modified boom sprayer mounted on the lower truss of a center-pivot. A PASS and an air-blast sprayer apply the same chemical formulations at the same rates per ha. Because a PASS injects no chemicals into the center-pivot, it is not chemigation. Unlike an air-blast sprayer that sprays out and up, a PASS sprays down, which should result in less spray drift. Because a PASS sprays over the tops of the trees, it places no restriction on row or tree spacing. Also, a PASS eliminates the pesticide exposure of a tractor driver spraying with an air-blast sprayer. Comparing capital costs of a PASS and an air-blast sprayer showed projected savings for the PASS of from $128/ha to over $248/ha as the orchard size increased from 7 ha to 29 ha. A PASS is much simpler than an air-blast sprayer which is pulled by a tractor, so the operating and maintenance costs for a PASS should be lower.
No reduction in yield and quality of pecan nuts or leaf mineral nutrient concentration occurred when 100 lb/acre of N was applied through a drip-irrigation system compared with 200 lb/acre applied either all broadcast or half broadcast and half fertigated. Yield of `Stuart', percentage kernel of `Schley', and nut size of both cultivars were increased by irrigation or irrigation and fertigation. The 100 lb/acre N-all-fertigated treatment resulted in less soil pH reduction and less loss of K, Ca, and Mg from soil underneath the tree canopy than broadcast treatments. No evidence of excessive soil pH reduction in the wetted zone of fertigated trees was noticed. Calcium and Mg were higher within than outside the wetted zone.
Carolina Bunch is a sweetpotato cultivar that combines high yield, excellent flavor and appearance with multiple pathogen and pest resistances. It is ideal for home or market gardens, because of its short vine and bunch habit that allow for production of high yields in a limited space. The roots are fusiform with uniform shape and a smooth, bright, light copper skin and dark orange flesh. When baked, the roots have a smooth texture and are sweet, moist and have excellent flavor and appearance. This sweetpotato can be grown virtually without pesticides. It has very high levels of resistances to southern root knot and other species of nematodes, Fusarium wilt, feathery mottle virus, sclerotial blight in plant beds, and Streptomyces soil rot. It has good resistance to many soil insects including several species of wireworm, Diabrotica, Systena, and flea beetles. In the southern US, it yields better than `Jewel' in a growing season of 110-120 days. Foundation roots are available in limited quantities from South Carolina Foundation Seed Association, Inc, 1162 Cherry Hill Rd, Clemson SC 29634-0393.