Reduction In Root Yield Research Articles

Response of Nine Sugarbeet (Beta vulgaris) Cultivars to Postemergence Herbicide Applications

A field experiment was conducted for 2 yr near Scottsbluff, NE, to evaluate the growth and yield response of nine commercial sugarbeet cultivars to five postemergence herbicide mixtures applied two times. Sugarbeet cultivars varied in their response to herbicides. Three of the five postemergence herbicide mixtures reduced sugarbeet leaf area at 9 wk after planting (WAP), while two treatments had no significant effect. Root yield reductions from herbicide treatments ranged from 3 to 11% averaged over the nine cultivars. Two applications of desmedipham plus phenmedipham at 180 plus 180 g/ha reduced root yield 3% compared to untreated plots. Two applications of clopyralid at 100 g/ha, triflusulfuron at 18 g/ha, or ethofumesate at 160 g/ha plus desmedipham plus phenmedipham resulted in a 17, 29, and 22% reduction in leaf area at 9 WAR respectively, and a 6, 8, and 6% reduction in root yield, respectively, compared to untreated plots. Sethoxydim at 280 g/ha plus desmedipham plus phenmedipham did not cause additional sugarbeet injury.

Wild Mustard (Brassica kaber) and Wild Oat (Avena fatua) Interference in Sugarbeets (Beta vulgarisL.)

Two furrow irrigated field experiments were conducted for two years at the Research and Extension Center, Powell, WY to determine the influence of various mixed densities and durations of wild oat and wild mustard interference in sugarbeet. Sugarbeet root yields were reduced by competition from all examined densities of wild oat and wild mustard, alone and in combination. Root yield reduction was less than additive with mixed densities of wild oat and wild mustard. Root yields decreased as the duration of interference after sugarbeet emergence from a mixed density of wild oat and wild mustard increased. Sucrose content of sugarbeet was not altered by competition. Based on regression analysis, the minimum time that a mixed density of 0.8 wild mustard and 1 wild oat/m of row can interfere with sugarbeet before causing an economic root yield loss was approximately 1.6 weeks after sugarbeet emergence.

Kochia (Kochia scoparia) and Green Foxtail (Setaria viridis) Interference in Sugarbeets (Beta vulgaris)

Two field experiments were conducted between 1990 and 1992 under sprinkler irrigation at the Research and Extension Center, Torrington, WY to determine the influence of mixed densities and durations of kochia and green foxtail interference in sugarbeet. Sugarbeet root yield and top weight generally decreased as densities of green foxtail and kochia increased whether alone or in combination. Reductions in sugarbeet root yield and above ground biomass from mixed densities of kochia and green foxtail were additive at the low and intermediate density but less than additive at the high density of either species. Sugarbeet root yield decreased as the duration of interference after sugarbeet emergence from a mixed density of kochia and green foxtail increased. Since sugarbeet plants were irrigated to avoid water stress and adequate nutrients were applied, it appears that kochia and green foxtail interfered with sugarbeet primarily for light, based on light and height measurements. Season-long as well as duration of interference did not show any significant effect on sucrose content. Based on regression analysis the lowest densities of kochia and green foxtail required to reduce root yield were approximately 0.3 and 0.06 plants/m of row, respectively. The minimum duration of time that 0.5 kochia and 3.0 green foxtail plants/m of row can interfere with sugarbeets before root yield is economically reduced was approximately 3.5 wk after sugarbeet emergence.

Effect of Shoot Removal on Shoot and Root Yields of Sweet Potato

SUMMARYExperiments on harvesting sweet potato as a green vegetable and as a root crop are described. Whole shoots yielded 62% more than shoot tips. Similar total shoot yields were harvested whether tip removal was at two, three or four week intervals. Root yield was decreased by 31 to 48% by removing shoot tips, while removing whole shoots led to root yield decreases of 48 to 62%. Harvesting shoots at two week intervals gave 72% reduction in root yield, compared with 50% with four week intervals. There were fewer and smaller tubers as the frequency of shoot harvests increased. There were varietal differences in response to shoot removal For reasonable yields of both shoot tips and tuberous roots harvesting shoot tips at four week intervals is recommended.

Rough Fescue Response to Season and Intensity of Defoliation

Rough fescue (Festuca scabrella Torr.) was subjected to 10 clipping regimes which varied in time or intensity of defoliation. The experiment was repeated at 2 sites for 3 consecutive years. Plant survival and vigor were evaluated the summer following defoliation. Clipping treatments involving weekly defoliation to a 5-cm stubble height from mid May to late June resulted in the greatest injury. Reduced injury occurred when clipping ceased in May or when 10 or 15 cm of herbage was retained. Season long defoliation to 20 cm or clipping only in the fall caused no apparent damage. Cutting in the fall plus spring resulted in greater injury than spring clipping alone on plants clipped from mid May to late June but a fall clipping effect was not observed consistently on plants clipped in May plus fall. Despite common observances of rapid decline of rough fescue (Festuca scabrella Torr.)' on overgrazed ranges, little work has examined defoliation response of this productive grass. Root and top growth yields were reduced by repeated monthly clipping to stubble heights of 4(1l/2), 7.5(3), or 12.5(5) cm (inches) in a greenhouse study (Johnston 1961). Magnitude of root yield reduction from the 12.5-cm treatment (comparable to 20% utilization) was much greater than reduction in herbage yield. Tiller production was depressed with the 2 most severe treatments but apparently was unaffected by the 12.5-cm stubble height treatment. The author advised caution in interpretation of clipping trials since 20% utilization on an Alberta fescue grassland indicated no depression of root or herbage yields. A long-term study (Johnston et al. 1971) showed that even light season-long grazing (0.8 ha/AUM) reduced rough fescue basal area after 16 years and the species was largely eliminated under very heavy grazing (0.2 ha/ AUM). Long-term consequences of a grazing trial could not be determined after 6 years on a central Albertan rough fescuewestern porcupine grass (Stipa spartea Trin.) rangeland (Bailey et al. 1980) but heavy (75%) utilization in either June or fall depressed grass production. Light (35%) utilization results were similar to the controls. Fescue yields the year following mowing in another Alberta study (Sinton and Bailey 1980) were greater than the control for the April 8 treatment; but cutting late in spring (April 27, June 1) or in fall (July 31, Oct. 18) resulted in production losses. Tiller density increased and leaf length decreased for all mowing treatments but the effects were most pronounced for the fall cuttings. Of the spring mowing treatments, leaf lengths were shortest and tiller stimulation was slightest for the June 1 mowing. In a previous paper, Stout et al. (1981) examined vegetative and reproductive growth of rough fescue. In the present study, response of rough fescue to a number of clipping regimes incorporating different times, frequencies and intensities of defoliation is compared.

Sugarbeet (Beta vulgarisL.) Response to Simulated Herbicide Spray Drift

Dicamba (3,6-dichloro-o-anisic acid), 2,4-D [(2,4-dichlorophenoxy)acetic acid], and picloram (4-amino-3,5,6-trichloropicolinic acid) were applied as simulated spray drift to sugarbeets at several growth stages. When applied at early growth stages 2,4-D tended to decrease root yield but decreased purity and extractable sucrose content by as much as 54% when applied at later growth stages. Dicamba at 0.14 kg ae/ha and 2,4-D at 0.28 kg ae/ha decreased extractable sucrose/ha and tended to decrease root yield at harvest while picloram at 0.028 kg ae/ha did not significantly reduce root yield or sucrose content at harvest compared to the control. All rates of 2,4-D from 0.035 to 0.28 kg ae/ha increased sucrose losses during post-harvest storage at 5 C and 95% relative humidity. Dicamba and picloram at 0.14 and 0.028 kg ae/ha, respectively, caused similar storage losses. Sugarbeets that are inadvertently exposed to 2,4-D, dicamba, or picloram spray drift during the growing season should be processed immediately after harvest.

Broadleaf Weed Interference in Sugarbeets (Beta vulgaris)

Interference within a mixture of equal densities of common lambsquarters (Chenopodium albumL.), kochia [Kochia scoparia(L.) Schrad.], and redroot pigweed (Amaranthus retroflexusL.) in sugarbeets (Beta vulgarisL. ‘Mono Hy D2’) was determined in a 3-yr field study. Yield of sugarbeet roots and sucrose per hectare decreased as intensity of competition from equal populations of these three weeds increased. At densities of 6, 12, 18, and 24 broadleaf weeds per 30 m of row, root yields were reduced 13, 24, 33, and 39%, respectively. Sucrose yields were reduced similarly. Fewer than three weeds per 30 m of row did not significantly reduce root yield. Reduction in root yield (Y) of sugarbeets caused by specific densities (X) of the three broadleaf weeds was predicted by using the linear equation Y = 1.64 + 1.88 X. The actual reductions in yield were always less than the predicted reductions when this equation was tested against 36 weed control systems because the competitive ability of broadleaf weeds that were treated with herbicides, but not killed, was suppressed during the growing season. By harvest, broadleaf weeds present in weed-control-system plots weighed an average of 75 to 85% less than broadleaf weeds present in nontreated plots.

Weed Control in Cassava Cultivation in the Subhumid Tropics

Abstract Field trials were carried out over a three year period in an alfisol in a subhumid tropical environment to evaluate the effectiveness of hand-weeding frequencies and several herbicides for weed control in cassava (Manihot esculenta Crantz). Uncontrolled weed growth caused 40% reduction in root yield of short, profusely branching cassava cultivar while a 68% reduction in root yield was observed in separate studies involving a tall non-branching cultivar. Two or three properly timed hoe weedings gave crop yields that were as good as keeping the plots weed free throughout the growing season. Although pre-emergence application of fluometuron at 2.0 to 3.0 kg a.i./ha or diuron at 2.0 kg a.i./ha used singly gave good weed control and crop yield, the efficacy of these herbicides was greatly improved by tank mixing each of them with alachlor or metolachlor at 3.0 and 2.0 kg a.i./ha respectively. Excellent crop yield was also observed where atrazine and metolachlor was applied pre-emergence at 2.5 kg a.i....

Planting Sugarbeets to Stand when Establishment is Erratic1

AbstractPlanting sugarbeets (Beta vulgaris L.) to stand is desirable if yields can be maintained. Low seeding rates eliminate the need to thin; however, yield and quality suffer if harvest stand is low. Sugarbeet stand establishment is erratic on the Southern High Plains. Therefore, planting to stand has been assumed to be unworkable. These studies were undertaken to determine the feasibility of planting to stand where establishment is erratic.Sugarbeets were planted to stand at a wide range of seeding rates and compared to an overplanted, handthinned check. Rows were 76‐cm apart on Pullman clay loam (fine, mixed, thermic Torrertic Paleustolls order Mollisol). Yield and harvest loss were determined on the center two rows of four‐row field plots with commercial harvesting equipment.Establishment of planted seed ranged from 31 to 63% and averaged 46%. Harvested mot yield and percent sucrose were reduced if harvest stand fell below four . More than 10.0 plants/m reduced root yield thin stands, less in thick stands, and least in near optimum stands (five to seven plants/m). Optimum seeding rate depended on establishment conditions; however, results were consistently good when planting to stand at 16.7 seeds/m of row. At this seediing rate, harvested sucrose yield ranged from 94.5 to 100.2% and averaged 97.8% of the hand‐thinned check. Thus, sugarbeets were successfully planted to stand even with low and erratic establishment. Planting sugarbeets to stand should be successful in other areas. The key to success is using a seeding rate high enough to guard against the lowest commonly expected establishment.

Response of an Astrebla Spp. grassland to heavy grazing by cattle and light grazing by sheep in North-west Queensland.

Botanical changes were measured in a semi-arid, Asrrebla lappacea (Mitchell grass) dominant grassland in the summer rainfall region of north-west Queensland that has been grazed traditionally by Merino sheep. Cattle have been introduced recently in large numbers and the effects of heavy grazing by cattle on these pastures in the dry season is unknown. A paddock v\as sub-divided and t\%o grazing treatments were applied in 1971. For seven consecutive years, steers were grazed at 70 to 141 beast grazing days per hectare per annum in the late dry season and compared with sheep grazing at equivalent to 17 to 37 beast grazing days per hectare per annum. Compared with light grazing, the heavy grazing treatment caused: an increased number but smaller Astrebia spp. plants; lower basal cover; reduced standing dry matter yield; reduced root yield; increased annual grass population and yield; reduced Aris- rida lar[f?jlia (feathertop) population; and an increased number of forbs.

Recurrent and Reciprocal Recurrent Selection in Sugarbeet1

Five cycles of recurrent selection (RS) for general combining ability and two cycles of reciprocal recurrent selection (RRS) in sugarbeet (Beta vulgaris L.) were evaluated. The fifth‐cycle RS synthetic produced significantly less sucrose than its source population, but combined equally as well as its source population with a group of four male sterile tester lines. The reduced sucrose yield of this synthetic resulted entirely from reduced root yield, partially accounted for by the estimated 20% inbreeding of this synthetic. Three second‐cycle RRS synthetics were produced from each of two source populations (A and B). These synthetics were generated on the basis of superior progeny performance for recoverable sucrose, root yield, and sucrose content, respectively. Recoverable sucrose increased relative to its source only in the second cycle synthetic for root yield from source A. Root yield improvements were made in two synthetics from the low yield source A. Improvement in sucrose content was made in two synthetics derived from the low sucrose source B. In no synthetic was there a simultaneous increase in root yield and sucrose content. Crosses between the A and B synthetics did not significantly exceed the performance of the superior source parent for recoverable sucrose or any of its components, root yield, sucrose content, or thin juice purity. Reciprocal recurrent selection was successful in improving the general and specific combining abilty of those yield components that were relatively low in the sources. Simultaneous improvement of all components for production and for combining ability was not achieved by either of the two breeding methods.

Predicting Sugarbeet Root Losses Based on Kochia Densities

The reduction in root yield (Y) of sugarbeets (Beta vulgarisL.) caused by specific densities (X) of kochia [Kochia scoparia(L.) Schrad.] was predicted by using the linear equation Y = 4.30 + 1.81 X. This equation was most accurate when the kochia density was 20 plants or less per 30.5 m of row. In 28 of 30 weed-control systems, where kochia densities ranged from 0.2 to 16.5 plants per 30.5 m of row, the predicted yield reductions were within 5% of the actual yield reductions.

Opposite Alluminum and Manganese Tolerances of Two Wheat Varieties1

AbstractAcid soil and solution culture studies showed that ‘Atlas 66’ wheat (Triticum aestivum L.) from North Carolina was more tolerant to excess Al but less tolerant to excess Mn than ‘Monon’ wheat from Indiana.In greenhouse pots of Al‐toxic Bladen soil (pH 4.6 to 5.1) the top yields of Atlas 66 were significantly higher (5% level) than those of Monon; liming the soil to pH 5.8, however, equalized top yields of the two varieties. In Mn‐toxic Zanesville soil (pH 4.7 to 5.2) the varietal yield difference was just the reverse. At pH 5.2 the tops of Monon plants had fewer leaf symptoms (rolling and chlorotic spots) and yielded significantly more than those of Atlas 66; at pH 5.9 or 6.9, however, the two varieties were not significantly different in top yield.In nutrient solutions containing between 4 and 32 ppm Mn at pH 4.6 the tops of Monon showed fewer leaf symptoms of Mn toxicity and yielded significantly more than those of Atlas 66, but with O or 2 ppm Mn added, the top yields of the two varieties were not significantly different. With Mn levels of 2 to 32 ppm, Monon root yields were significantly higher than those of Atlas 66, but with no Mn added the two root yields were not significantly different. At all Mn levels of 2 to 32 ppm in solution both tops and roots of Monon contained higher Mn concentrations than those of Atlas 66, but Monon plants showed less injury. For example, in Monon tops 2,561 ppm Mn was associated with a yield reduction of 12%. In Atlas 66 tops 1,250 ppm Mn (the highest concentration reached in Atlas 66) was accompanied by a yield reduction of 21%. In Monon roots 8,534 ppm Mn was associated with a root yield reduction of 20%, but 7,172 ppm Mn in Atlas 66 roots coincided with a 45% reduction in root yield.Tolerance to one acid soil factor in a given plant genotype does not necessarily mean tolerance to another.

Some Effects of Preharvest Foliage Sprays of Maleic Hydrazide on Proximal Dominance and Sprout Inhibition of Sweet Potatoes

1. Maleic hydrazide at 4000, 8000, and 16,000 p.p.m. applied as foliage sprays to Porto Rico variety sweet potatoes 1 month before harvest gave highly significant reductions in the slip production of roots bedded after storage. The use of 2000 p.p.m. resulted in a loss of proximal dominance along the sweet-potato root, accompanied by normal slip production. 2. With the Gold Rush variety a foliage spray of 2000-p.p.m. maleic hydrazide resulted in a significant increase in both early and late slip production. Highly significant reductions in slip production followed the use of an 8000-p.p.m. spray. 3. No reduction in root yield of sprayed plants resulted from any of these treatments on Porto Rico and Gold Rush varieties of sweet potatoes. The possibilities of the dual role of maleic hydrazide in greater slip production and control of storage sprouting are discussed.