Uneven Stands Research Articles

Plant population density in cotton: Addressing knowledge gaps in stand uniformity and lint quality under dryland and irrigated conditions

A recent literature review and data synthesis better defined the yield curve with plant population density in cotton (Gossypium hirsutum L.), but it also highlighted gaps in knowledge. Few cotton plant population studies have been conducted in relatively low-yielding dryland conditions; fewer have considered the impact of uneven crop stands, which are common in actual field conditions due to planting equipment errors and seed/plant mortality; and population reports that include fiber quality measurements by Advanced Fiber Information System (AFIS) testing are lacking (rather than just the standard High Volume Instrument (HVI) measurements). To address these issues, a study was conducted in North Texas, USA with treatment combinations of two irrigation levels (0% and 90% ET replacement), five plant population densities (15,000, 30,000, 60,000, 90,000, and 120,000 plants ha-1), and two stand uniformities (even and uneven plant-to-plant spacing within rows). Canopy development was tracked by unmanned aircraft system (UAS) measurements, late-season measurements were taken of boll density and size, and lint yield and quality measurements were collected at maturity. Lint yield was unaffected by plant population density in 2020 (i.e. 15,000–120,000 plants ha-1), whereas an interaction between irrigation and plant population occurred in 2021. Lint yield was reduced by 19% with 15,000 plants ha-1 relative to 120,000 plants ha-1 under only irrigated conditions in 2021. There was no substantial or consistent effect of stand uniformity on any response variable in either year. Poor stand quality is often the basis for terminating and replanting or replacing troubled cotton crops, but these results suggest this is not justified when overall population density is 30,000 plants ha-1 or greater, depending on production environment. The risk of yield loss is clearly greater when overall plant density decreases below this level, especially in higher-yielding conditions, but the economic tradeoffs of replanting or replacing the crop must be considered. In the cotton plant, yield compensation for low plant density and uneven stands occurred primarily by increased boll number per plant and secondarily by increased boll size. Fiber quality parameters as measured by HVI and AFIS were minimally and inconsistently affected by population density and stand uniformity, suggesting that population dynamics are not critical factors cotton producers must consider in optimizing the fiber quality of their product.

Suppression subtractive hybridization and comparative expression of a pore-forming toxin and glycosyl hydrolase genes in Rhizoctonia solani during potato sprout infection

Rhizoctonia solani is a plant pathogenic fungus that causes black scurf on tubers and stem and stolon canker on underground parts of potato plant. Early in the season, the fungus attacks germinating sprouts underground before they emerge from the soil. Damage at this stage results in delayed emergence of weakened plants with poor and uneven stands. The mechanism underlying this phenomenon has been investigated in this study by coupling a cDNA-suppression subtractive hybridization (SSH) library to differential screening to identify transcripts of R. solani that are down-regulated during infection of potato sprouts. We report on the identification of 33 unique genes with functions related to carbohydrate binding, vitamin synthesis, pathogenicity, translation, ATP and nucleic acid binding and other categories. RACE-PCR was used to clone and characterize the first full-length cDNA clones, RSENDO1 and RSGLYC1 that encode for an eukaryotic delta-endotoxin CytB protein and an intracellular glycosyl hydrolase, respectively. Quantitative real-time PCR revealed the down-regulation of RSENDO1 during infection of potato sprouts and the up-regulation of RSGLYC1 when the fungus was grown on a cellulose-based nutrient medium. In contrast, additional experiments have highlighted the down-regulation of RSENDO1 when R. solani was co-cultured with the mycoparasite Stachybotrys elegans and the bacterial antagonist Bacillus subtilis B26. These results advance our understanding of R. solani-potato interaction in subterranean parts of the plant. Such approaches could be considered in building an efficient integrated potato disease management program.

Conseils pour l’échantillonnage des arbres en peuplements purs et réguliers en vue de l’estimation de leur sensibilité au climat par analyse dendroécologique

La dendroécologie consiste à estimer la sensibilité au climat d’un peuplement forestier en construisant une chronologie moyenne de croissance à partir d’un échantillon d’arbres. Les choix d’échantillonnage peuvent avoir de fortes conséquences sur l’estimation du signal climatique contenu dans les chronologies de largeurs de cerne et donc des relations croissance-climat. La baisse de la taille de l’échantillon réduit la qualité de l’estimation du signal climatique, ce qui a pour conséquence de diminuer la corrélation entre la chronologie moyenne de croissance et les séries climatiques ; ce biais et sa correction sont décrits dans cet article. Cela augmente aussi le risque de mal estimer la significativité de ces corrélations. Le biais relatif à la taille de l’échantillon n’est pas constant entre les essences et les conditions environnementales dans lesquelles les peuplements échantillonnés ont poussé. En effet, les conséquences de la réduction de l’échantillon sont plus fortes pour les essences sciaphiles que pour les essences héliophiles, pour les contextes environnementaux peu limitants pour la croissance, et potentiellement pour les peuplements hétérogènes en structure, en âge et en composition. Au final, pour s’assurer de la validité des résultats d’une analyse dendroécologique, la stratégie d’échantillonnage doit être réfléchie en fonction de l’essence objectif et des caractéristiques écologiques de la zone d’étude et du peuplement.

Estimation du prix des bois sur pied en fonction des caractéristiques du lot : le cas du Hêtre en Lorraine avant les tempêtes de 1999

On dispose en France de nombreux modèles de croissance des arbres et peuplements forestiers mais on manque cruellement de modèles de prix des bois sur pied. Un modèle a été élaboré pour le Hêtre en Lorraine et estimé sur la base des prix de l’année 1996. Il se présente sous une forme suffisamment générale pour être adapté à d’autres essences et circonstances. Il s’applique à des peuplements aussi bien irréguliers que réguliers. Il prend en compte la valeur des tiges et des branches, la qualité du bois résultant de l’état dimensionnel et de l’histoire sylvicole des arbres, la productivité de l’exploitation. De ce fait, il est susceptible d’expliquer la différence de valeur entre plusieurs lots de caractéristiques bien distinctes. Il serait utile que ce type de modèle soit développé pour les principales essences et régions françaises.

Response of Maize and Soybean to Variability in Stand Uniformity

The literature indicates variable results in response to uneven stands. We tested the hypothesis that the effect of uneven stands on grain yield varies depending on the vegetative and reproductive plasticity of the species and cultivars. Treatments consisted of a uniform control, nonuniform plant spacing between plants, and uneven seedling emergence. For maize (Zea mays L.), average yield per plant (Yp) decreased 0.68 g for every unit increase in percentage coefficient of variation (CV) for vegetative biomass per plant (Vp). Contrarily, soybean [Glycine max (L.) Merr.] Yp was not affected by increments in plant size variation. A model based on the relationship between Yp and Vp and on mean and CV for Vp was used to estimate the effect of nonuniformity on grain yield in maize and soybean cultivars. Based on these models and assuming constant average Vp with a normal frequency distribution throughout different stand uniformity treatments, increases in CV for Vp resulted in less grain yield in maize but not in soybean. Reductions in vegetative biomass produced further yield drops according to the specific relationship between Yp and Vp. The effect of unevenness in plant sizes on maize grain yield would depend on the characteristics of the hybrid. A stable hybrid is characterized by low decreases in Vp in response to heterogeneity, low threshold Vp for prolificacy and for grain yield, and a low curvature in the Yp/Vp relationship.

An operative framework for total hicksian income measurement: application to a multiple-use forest.

A methodology for estimating total hicksian income in multiple-use forests is presented. The approach consistently incorporates commercial as well as non-commercial economic values and enables the measurement of national accounting aggregates taking into account variation in man-made and natural capital. Innovative solutions are developed (i) for the estimation of non-market values, such as recreation, where an attempt to determine exchange values has been made simulating markets, (ii) for timber, where standing timber valuation methods have been extended to cover uneven stands, and (iii) for carbon fixation valuation, where only permanently fixed carbon after 1990 has been taken into account. The methodology is applied to a multiple-use pinewood in the Guadarrama mountains, near Madrid (Spain). Timber, cattle grazing, hunting, recreation, carbon fixation and conservation values are measured and integrated in the accounting system, using primary microeconomic data from the case study. Results indicate the importance of non-commercial income, which accounts for 51% of the total income, and the social relevance of the analysed forest, implying that only 31% of the total income generated is appropriated by the forest owner.

Potato Seed Piece Treatments for Controlling Rhizoctonia solani Infections

Rhizoctonia solani infection of potato causes seed piece decay and stem and tuber lesions, resulting in delayed emergence and uneven stands, low-vigor plants and unmarketable tubers. Rhizoctonia prevention effectiveness of three fungicide/fir bark dusts and nontreated tubers were compared on three varieties. Seedpieces of Viking, Atlantic and Norkotah 278 were treated and planted in separate commercial fields. A randomized complete-block design with four replications with four 26-foot rows per treatment plot included four treatments: 0.5 lb Maxim, 1.0 lb Tops MZ, and 1.5 lb Nubark Captan dust/100 lb seed. Plant stems, stolons and tubers were examined for Rhizoctonia infection at the tuber initiation stage and tubers were examined again at mature stage. Maxim and Tops MZ reduced stolon infection in Atlantic and Norkotah 278 and reduced stem infection in Norkotah 278. Plants from Maxim treated tubers produced more stems/plant in Norkotah 278 and produced more weight of tubers weighing less than four oz in all three varieties. Differences in seed tuber conditioning and mechanical damage in seed handling increase variability of treatment effects. Repeated testing of potato seed piece treatments in Texas High Plains conditions is the best way to confirm potential of beneficial effects of seed treatment.

Foliar Sprays to Control Insects in Fall Peppers, 1995

Abstract Peppers were transplanted on 31 Jul at the Eastern Shore Agricultural Research and Extension Center, Painter, VA. Each plot consisted of two 25ft long rows with 3ft between row spacing and 1ft between plant spacing. Each plot was bordered on each side by an untreated guard row and replicated 4 times in a RCB design. Treatments were applied on the dates indicated in the table with a backpack sprayer using 3 hollow cone nozzles/row and delivering 60 gal water/acre at 40 psi. Evaluation criteria consisted of hand-harvest of marketable fruit on 10 healthy, uniform-sized plants/row (.00062 acre) and GPA counts on 5 randomly picked leaves/plot on 06 Oct. Harvesting was done in this manner due to uneven stands in some plots due to the drought.

Growth of early potatoes from different portions of seed tubers I. Emergence and plant stand

Several of the recently released early potato cultivars in Ontario are prone to poor and/or uneven stands. Studies were undertaken to investigate these problems. Basal seed halves of Jemseg and Yukon Gold were found to emerge an average of 4.6 and 5.7 days, respectively, later than shoots from apical halves or whole tubers in 3 years of study. No practical difference in emergence was found among tuber portions of Superior. Sums of squares attributed to seed portions accounted for 51.1 percent of the variation of days to 50 percent emergence for Jemseg, 50.3% for Yukon Gold and 8 percent for Superior. No difference in final percent emergence was found among the various seed portions of Jemseg and Superior. Cultivars with strong apical dominance or dormancy appear prone to uneven emergence.

Growth of early potatoes from different portions of seed tubers II. Yield

Several of the recently released early-potato (Solanum tuberosum L.) cultivars used in Ontario have produced uneven stands which have been shown to be a result of delayed emergence from basal end seed pieces. A study was conducted to evaluate the effects of seed portions on the yield of three early potato cultivars, Jemseg, Superior and Yukon Gold. Yield of plants from basal seed pieces was lower than that from apical seed pieces or whole tubers for Jemseg and Yukon Gold during several sequential harvests. With Superior, cut seed portions yielded less than whole seed. Number of stems per plant was lower for basal plants of Jemseg. Tubers with strong apical dominance or dormancy such as Jemseg and Yukon Gold are prone to differences in yield among seed portions.

Tillage System and Date of Planting Effects on Yield of Corn on Soils with Restricted Drainage1

AbstractIt has been reported that no‐tillage corn (Zea mays L.) production on poorly‐drained soils results in more uneven stands and slower early growth as compared to conventional tillage methods. A field study was established in 1979 at Princeton, KY, on a Johnsburg silt loam (Aquic Fragiudults) intergrading to a Tilsit silt loam (Typic Fragiudults), to compare corn planting dates under no‐tillage (NT) and conventional tillage (CT) systems. For the NT system, a yield increase trend was observed as planting date progressed from the first planting date (late April) to the second (mid‐May). Grain yields from conventionally tilled treatments decreased with delayed planting dates. No‐tillage corn performed better than CT corn during drier growing seasons, and conventionally tilled corn produced yields equal to or slightly higher (no significant differences) for early planting dates, during years in which wet and cool climatic conditions existed during the early part of the growing season. There appears to be a greater risk associated with early planting dates for NT corn on these soils. From a management viewpoint, corn planting on these cooler soils with slow internal drainage can be delayed due to excessive wetness without substantial yield losses if NT management is used.

Phytotoxicity of Lorsban to Direct-Seeded Cabbage, 1984

Abstract Grower concerns for reduced and uneven stands of Lorsban-treated cabbage in the spring of 1984 prompted a test to determine the potential for phytotoxicity of Lorsban to direct-seeded cabbage. The plots were seeded on 21 Sep using a John Deere Flexiplanter unit mounted on a tractor. The soil was wet and planting conditions were marginal. These planting conditions were similar to the conditions in the spring when the uneven stands had occurred. Plots consisted of 30-ft single-row treatments replicated 3 times in a randomized complete block design. The entire plot was planted twice, one plot being irrigated with 1 inch of water on 24 Sep and the other left unirrigated. Treatments in each plot consisted of 2 series of 5 rates of Lorsban 4E, plus an untreated check. Lorsban 4E for 1 of the series of treatments (Lorsban I) was donated by a grower who had noted uneven stands. Lorsban 4E for the other series (Lorsban II) was supplied to us by Dow Chemical Corp. The Lorsban treatments were applied in 30 gal of water/acre as a 2-3 inch band over the furrow after planting. A CO2 power sprayer mounted on wheels with an attached speedometer was used to apply the spray. All water and insecticide calculations were made on a 36-inch row width basis. Stand counts were taken and plant heights were measured from the center 20 ft of each treatment on Oct 10, Fifteen plants/treatment were measured. Heights given are in inches.

Soybean Plant Damage and Yields as Affected by Metribuzin and Seed Quality1

AbstractCrop safety is a concern when metribuzin [4‐amino‐6‐tert‐butyl‐3‐(methylthio)‐as‐triazin‐5(4H)‐one] is used as a preemergence for weed control in soybeans [Glycine max (L.) Merr.] on coarse textured soils having a low organic matter content. Six field experiments were conducted on soils that were Typic Hapludults, Typic Udifluvents, and Typic Paleudults. In each experiment three soybean cultivars were used to determine if excessive metribuzin rates interact with various seed quality factors to influence the margin of safety to soybean plants. The cultivars were ‘Bragg’, ‘Bossier’, and ‘Hampton 266A’. Seed quality factors included 1 and 2‐year‐old seed with different germination percentages, physically damaged vs. nondamaged seed, and large vs. small seed sizes. Metribuzin was applied at 0.0, 0.84, and 1.68 kg/ha to the soil surface immediately after planting.In most experiments, both metribuzin and seed quality factors affected plant damage ratings, final stands, mature plant heights, and grain yields. In seed germination and seed damage experiments, none of the seed quality ✕ metribuzin interactions were significant for any of the measured parameters. However, in the seed size experiments, metribuzin caused more plant damage and a greater reduction in final stands and heights of plants from small than from large seed, but grain yields were not affected. From a practical standpoint, this may be of little or no importance since seed size extremes in these studies probably do not occur in normal seed lots, and plant performance differences did not appear to warrant separating specific seed sizes from a given lot. Our results suggest that metribuzin ✕ seed quality interactions do not frequently result in increased plant damage, reduced stands and height of plants, and lower grain yields, but their effects are additive. Therefore, uneven stands and apparent herbicide damage symptoms may be diagnosed only as herbicide damage when actually seed quality factors may be contributing to the problem.

Response of Sunflower to Uniformity of Plant Spacing1

AbstractPlant spacing in the row is variable in most sunflower (Helianthus annuus L.) fields. The amount of yield loss from moderately uneven stands of sunflower should be known before undertaking expensive techniques to increase uniformity of plant distribution. The objective of this research was to measure the effects of uniformity of plant distribution on sunflower seed yield, plant growth, and seed quality. Four plant distributions of oilseed and nonoilseed cultivars in rows 76 cm apart and in a population of 49,000 plants/ha were established at five locations in Minnesota in 1979 and 1980. Soils were Typic Haplaquolls, Aerie Calciaquolls, and Aerie Haplaquepts. Plant distributions were: single plants 27 cm apart; paired plants 53 cm apart; five plants each 13 cm apart, 80‐cm space; seven plants each 9 cm apart, 80‐cm space, single plant, 80 cm space. Uniformly spaced, single plants lodged least and produced heads of lowest moisture percentage at harvest and seed of highest yield and oil percentage. Yield reductions from uneven plant distributions ranged from none to 31% and averaged 10%. Greater lodging was the most consistent detriment of nonuniform plant spacing. The magnitude of differences in seed quality among the plant distributions was small and consequently of relatively little economic importance.

The effects of soil compaction on the emergence, growth and yield of sugar beet and peas

AbstractIt is generally recognised that soil compaction may decrease yield of sugar beet and peas. The effects of soil surface compaction after drilling on the emergence, growth and yield of sugar beet in 1977–1978 and peas in 1976–1977 were investigated in field experiments. Compaction significantly decreased emergence in both crops and resulted in uneven stands. Root growth early in the season was delayed and final depth of water extraction restricted. At final harvest, yields of roots and sugar in sugar beet and yields of vining peas were reduced by up to 45 and 50%, respectively. The decrease in yield in sugar beet in 1977 was due mainly to decreased population and uneven distribution of plants, rather than the continued direct effects of compaction on individual plants, whereas in 1978 individual plants were also decreased in size. In peas both factors were of similar importance.

Delayed Dormancy as a Probable Cause of Uneven Stands in Planted Potatoes

American Journal of BotanyVolume 14, Issue 5 p. 284-286 Article DELAYED DORMANCY AS A PROBABLE CAUSE OF UNEVEN STANDS IN PLANTED POTATOES Arthur T. Evans, Arthur T. Evans Department of Botany, South Dakota State College, Brookings, South DakotaSearch for more papers by this author Arthur T. Evans, Arthur T. Evans Department of Botany, South Dakota State College, Brookings, South DakotaSearch for more papers by this author First published: 01 May 1927 https://doi.org/10.1002/j.1537-2197.1927.tb04844.xAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume14, Issue5May 1927Pages 284-286 RelatedInformation