Seed Cotton Production Research Articles

Effects of simulated insect damage and weed interference on cotton growth and reproduction

SummaryEarly‐season insect pests of cotton (Gossypium hirsutum L.) crops, including Lepidoptera larvae and mirids, feed on vegetative buds. The loss of vegetative buds transiently delays the plant's development and growth and has the potential to reduce its competitive ability. Yield reductions due to weed interference and insect damage, therefore, could be greater than expected from the additive effects of weeds and damage acting separately. Three varieties, two levels of weed infestation, and two levels of simulated damage were combined in a factorial experiment designed to assess the responses of cotton plants to the combined effects of damage and weeds. Weed treatments were: with (+W) and without weeds (‐W), and damage treatments included: undamaged control (‐D) and damaged plants (+D) which had their active vegetative buds removed at 30 and 49 days after sowing.Variety and interactions between variety and other factors were normally nonsignificant for all the response variables measured in this experiment. Cotton height, width, production of flowerbuds and production of fruit were all affected by both damage and weeds. While the effects of damage on these growth variables were transient, the effects of weeds normally increased with time throughout the season. Non‐additive effects of weeds and damage were minor for plant height and width, and large for flowerbud and fruit production.At maturity, weed dry matter ranged from about 20 g m‐2 (‐W treatments) to 300 gm‐2 (+W), cotton dry matter from 144 gm (+W+D) to 945 gm‐2 (‐W‐D), and seed cotton production from 54gm‐2 (+W+D) to 417 gnT‐2 (‐W+D). Damage did not affect vegetative dry matter and marginally increased seed production in ‐W plots. Non‐additive effects of weeds and damage were negligible for vegetative dry matter but highly significant for seed production (P < 0.0001). These contrasting responses of vegetative and reproductive growth are in agreement with neighbouring models of plant competitive interactions that emphasise the effects of neighbour interference on the fecundity of target plants that are not mediated by changes in target‐plant size.

Population-level compensation after loss of vegetative buds: interactions among damaged and undamaged cotton neighbours.

Population-level compensation occurs "when herbivore attack on one individual allows another individual to grow more rapidly". This form of compensation was investigated in high and low density cotton crops subjected to three treatments: (i) undisturbed controls, (ii) uniformly damaged, in which all plants were damaged, and (iii) non-uniformly damaged, in which every second plant was damaged. Damaged plants had their vegetative buds manually removed to simulate damage by Helicoverpa spp. (Lepidoptera). Removal of vegetative buds did not reduce seed cotton production per unit ground area. In uniformly damaged crops, compensation was essentially the result of profuse branching after release of apical dominance and activation of axilary buds. In non-uniformly damaged crops, population level mechanisms acted that involved strong plant-plant interactions. At both plant densities, undamaged plants grown alongside damaged neighbours accumulated more root and shoot biomass and produced more seed cotton than undamaged plants in uniform crops. Different degrees of symmetry in the relationship between damaged and undamaged neighbours lead to different degrees of compensation, viz. seed cotton production of non-uniformly damaged crops ranged from 98 to 125% of that in controls. At high plant density, neighbour status also affected flowerbud initiation and/or retention. Changes in competitive relationships as well as early detection of and response to neighbour status were likely involved in these responses.

Effect of windbreak on the yield of cotton crop in semiarid regions of Haryana

The beneficial effects of shelterbelts and windbreaks have been convincingly demonstrated in the temperate regions of the world. Investigations conducted on the biological effects of windbreaks are relatively few in arid and semiarid zones. In the semiarid regions of Haryana under Social Forestry programmes large scale plantations along roads, canals, fields, etc. were undertaken. In this region, an area having a windbreak of Dalbergia sissoo (18 years old) was selected and cotton was raised in the agricultural fields. The tree belt is able to reduce the windspeed by 15 to 45% depending upon season and wind speed. Observations on morphological characters and crop yield revealed that the belt height had a significant effect on plant growth. In general growth and cotton productivity increased upto distance of four times the tree height to the leeward of belt. Depending upon the orientation of tree belt, an increase in cotton yield was found to be 4 to 10%. Plant growth (in terms of leaf area, leaf number, plant height) and yield (seed cotton production) were observed to be high in sheltered area as compared to open fields. The results indicate that windbreak establishment should be adopted and integrated to a whole farming system, in semiarid regions.

Effects of Nitrogen, Dicyandiamide, and Tillage on Cotton Nitrogen Concentration and Yield

AbstractConservation tillage has the potential to increase N leaching from sandy soils by increasing water infiltration. The nitrification inhibitor dicyandiamide (DCD) can reduce this risk, but cotton (Gossypium hirsutum L.) may be sensitive to DCD. Field studies were conducted at the E.V. Smith Research Center in Macon County, AL on a Norfolk soil (fine, loamy, siliceous, thermic Typic Paleudult) to determine the effects of DCD on cotton N concentration and yield of conventional and strip‐till cotton. Nitrogen treatments included four preplant N rates (0,67,100, and 134 kg ha−1) with and without DCD (10% of N rate). Leaf N concentration was generally greater in treatments receiving N fertilizer than no N; however, regressions between N concentration and N fertilizer were not always significant. Whole plot effects on yield due to tillage were significant. Optimum N rate for seed cotton production was 67 kg ha−1 N in 1984 and ranged between 100 and 134 kg ha−1 N in 1985 and 1986. The application of DCD decreased yields by 30% in 1984. At the 134 kg N ha−1 rate in 1985, DCD increased yields by 24%. In 1986 seed cotton yields in the strip‐till treatment receiving 134 kg ha−1 N were 20% less with DCD than without. It is concluded that application of DCD is beneficial, with typical rainfall patterns, if high rates (13 kg ha−1) are used. However, if rainfall is less than the historical average during first square to first bloom stage, DCD application has little effect or is detrimental to seed cotton yield.

Picker Harvest of Bedded Cotton with Various Row Spacings

ABSTRACT THIS research concerns the picker harvest of a picker variety of cotton grown in one, two, or three rows per 1-m bed. The rows were spaced one row per 1-m bed, two rows spaced 20.3 cm apart on the 1-m bed, and three rows spaced 10.2 cm apart on the 1-m bed. At harvest, the plant height and width decreased with decreases in row spacing. Total seed cotton production and net harvested yields showed increasing trends (not signifi-cant) with decreasing row spacing. Harvest losses also in-creased with decreases in row spacing.

Influence of rates and sources of nitrogen on growth, nitrogen uptake and yield of cotton (G. hirsutum L.)

AbstractField experiments on cotton with different forms of urea applied at rates of 40 and 80 kg N/ha were carried out. The results indicated that application of nitrogen increased plant height, dry matter accumulation, number of bolls per plant, seed cotton yield and nitrogen uptake. The proportion of dry matter and nitrogen in the stem was increased and that in the leaves was reduced by N application. Sulphur coated urea (all applied at sowing) was about the same in effect as N‐Serve treated urea and gave significantly more seed cotton yield than untreated urea, neem cake treated urea and sulphur coated urea (applied in two splits). Nitrogen efficiency as expressed by kg seed cotton production per kg N applied was greater with 40 kg N/ha rate than with 80 kg N/ha. Sulphur coated urea (all applied at sowing) gave the highest nitrogen efficiency followed by N‐Serve treated urea.

The effect of level of nitrogen nutrition on earliness in upland cotton (Gossypium hirsutum L.)

The responses of both morphological and product quantity measures of earliness in two cotton cultivars to nitrogen stress applied either continuously or over specific developmental stages are reported. Continuous nitrogen stress increased the number of days to appearance of the first flower bud and first flower in both cultivars, had little or no effect on the main-stem node at which the first-fruiting branch appeared, and increased flower bud shedding only in the less determinate early cultivar Rex. The total number of fruiting points produced up to first flower appearance was reduced by nitrogen stress in both cultivars. Nitrogen stress from planting to appearance of the first flower bud greatly increased the time taken for flowering to occur at the first 30 fruiting points through delaying first flower appearance in both cultivars and increasing the horizontal flowering interval in Rex. Nitrogen stress applied later generally had little effect on this earliness index. Nitrogen stress from planting to first flower bud appearance strongly reduced the production rate index in Rex. However, nitrogen stress from first flower bud to first flower appearance resulted in a rapid rate of seed cotton production in both cultivars. Stimulation over the control was particularly marked in cultivar Bar 7/8. The relationship between earliness index and production rate index was explored, and the nitrogen effects on these indices evaluated. The combined use of these indices in field trials to identify factors limiting earliness is advocated.

Use of Sprinklers to Study the Influence of Population Density Upon Seed Cotton Production in an Arid Area1

AbstractThe growing period for cotton (Gossypium hirsutum L.) has been shortened by 2 months in the Imperial Valley because of an invasion by pink bollworm. The law now requires that cotton residue be incorporated into the soil early to lower the number of overwintering larvae. The shorter period for floral development led to reexamination of yield potential under different plant spacing. Defoliants, fertilizer, desiccants, and insecticides for pink bollworm control and water were applied through the sprinkler system. Randomized block designs of ‘Stoneville 213’ and ‘Paymaster 111A’ included plant densities of 15,000, 60,000, 242,000, and 969,000 plants/ha on a flat soil surface. Seeds were placed by hand at 2 per dibble in a square grid pattern. The bolls per plant were significantly affected by plant density. The effect of plant density on boll weight was significant on Paymaster 111A but not on the Stoneville 213. The highest seed cotton yield occurred where the plants produced the greatest number of bolls per hectare. For both varieties the highest yield occurred in the 242,000/ha treatment, with 4,870 kg/ha in Stoneville 213, and 4,228 kg/ha in Paymaster 111A. A trend of lower micronaire in the highest density was noted in each variety.

Genetic Recombinations in a Hybrid Involving Three Species of Gossypium1

SynopsisThe F2 and F3 progenies of Gossypium arboretum‐thurberi‐hirsutum were extremely variable in plant habit, seed cotton production, and all lint properties. There is an opportunity to develop from this material new combinations of lint length, strength, and fineness which should be stabilized into relatively true breeding stocks and later used in a breeding program to improve the quality of cotton.