Increased Boll Weight Research Articles

Modeling of cotton yield responses to different irrigation strategies in Southern Xinjiang Region,China

Southern Xinjiang region represents a prototypical oasis agricultural area, and cotton is the primary cash crop. The current cotton water productivity for this area remains room for improvement. In order to refine cotton drip irrigation strategy in Southern Xinjiang, this study combined field experiment with crop model simulation and prediction. In this experiment, two irrigation methods, furrow irrigation and drip irrigation, and different degrees of deficit irrigation were set up. The impacts of soil moisture on cotton yield and quality were assessed, with the additional utilization of the Root Zone Water Quality Model (RZWQM2) for simulating irrigation scenarios and predicting cotton yield field data showed that during the 2021–2022 growing season, drip irrigation significantly increased boll weight, yield, and Water Productivity compared to furrow irrigation. The deficit irrigation with 90 % of full irrigation during the flowering period resulted in the highest yield among all drip irrigation treatments, while simultaneously improving the fiber quality. The RZWQM2 model was calibrated and validated using 2021 and 2022 cotton field experimental data, respectively. The calibrated and verified RZWQM2 model shows good performance. In terms of soil water storage, cotton yield and evapotranspiration. The simulated value output by the model is close to the measured value in the field. Model prediction data suggest that there is still room for improvement in cotton yield, accompanied by an increase in evapotranspiration. But deficit irrigation below 80 % of the full irrigation quotas poses a notable risk of yield reduction. Targeting higher yields, the predicted scenario suggests an increase in water application (irrigation quota:314.8 mm). Additionally, this study proposes irrigation regimes with water savings of 10 % and 20 %, with irrigation quotas of 290.5 mm and 266.5 mm during the growth period, respectively. Based on this study, we provide a more detailed and reliable water-saving scheme for cotton drip irrigation in southern Xinjiang region.

Foliar application of phosphoric acid mitigates oxidative stress induced by herbicides in soybean, maize, and cotton crops

Foliar fertilization presents a potential solution in alleviating oxidative stress triggered by herbicide exposure. Enhancing our comprehension of the interplay between foliar fertilization, oxidative stress, and herbicide application is pivotal for enhancing crop yield. Carfentrazone, a herbicide, prompts the buildup of reactive oxygen species, leading to detrimental effects on cell membranes and the manifestation of chlorotic spots on leaves. This research administered carfentrazone-ethyl to soybean, maize, and cotton to induce stress. The herbicide application was followed by foliar application of phosphorus (H3PO4) to evaluate its effect on phytotoxicity recovery. The evaluations included leaf nutritional analyses, gas exchange measurements (photosynthesis, stomatal conductance, substomatal CO2 concentration, and Leaf transpiration), photosynthetic pigments (chlorophylls and carotenoids), oxidative stress indicators (MDA, H2O2, SOD, CAT and APX), and productivity parameters (height, number of branches, pods, grains, 100-grain weight, and yield), in addition to the activity of the enzyme Rubisco (ribulose-1,5-bisphosphate carboxylase/oxygenase), which is crucial for carbon fixation and the photosynthetic efficiency of plants. Phosphorus (P) improved chlorophyll levels by up to 28.8% and Rubisco activity by up to 24.8%, leading to increases in the net photosynthetic rate by up to 40.2%, stomatal conductance, water use efficiency, and carboxylation. In addition, foliar P fertilization enhanced antioxidant metabolism, with reductions in markers of oxidative stress (H2O2 and MDA) by up to 39.1%. Collectively, these effects of foliar P fertilization increased the productivity of the three crops by up to 55.9%, indicating that foliar supplementation with P is an effective strategy to mitigate phytotoxicity symptoms.. In soybeans at the V4 and V6 stages, it has been shown to improve net photosynthesis, enhance Rubisco activity, and reduce oxidative stress. In maize, the V4 stage proved to be more effective, increasing Rubisco activity and improving productivity. For cotton, the B1 stage was more beneficial, resulting in increased boll weight and fiber yield. This study introduces an innovative approach of foliar P-supplementation to mitigate herbicide-induced oxidative stress in crops. This management strategy enhances crop resilience, improves yield stability, and provides a sustainable solution to a critical challenge in modern agriculture.

Changes in carbohydrate distribution of cotton and increase in boll weight reduced yield loss under high temperature.

Cotton yield is sometimes unresponsive to high temperature (HT) that induce significant reductions in fruit retention. To investigate the underlying mechanisms, a greenhouse experiment was conducted with two temperature regimes (control, control treatment, 28 °C; HT, 34 °C) for 7 days. Results showed HT did not significantly influence cotton yield, but remarkably reduce boll number and increase boll weight. 13C distribution ratio of the leaf subtending to cotton boll (LSCB) decreased while that of cotton boll increased under HT. Transcriptomic and proteomic analyses of LSCB revealed up-regulated genes involved in cytokinin and jasmonic acid synthesis, as well as SWEET15 (GH_D01G0218), which positively regulated photosynthesis and transport photosynthate, ultimately leading to increased boll weight. After 7 days recovering from HT, 13C distribution ratio of LSCB increased while that of cotton boll decreased. However, the boll weight still increased, which was related to the increased amylase and sucrose phosphate synthase activities and up-regulated sucrose transport genes in main-stem leaf and capsule wall. Thus, both the accelerated sucrose synthesis and transport in LSCB under HT and the increased sucrose supply ability in main-stem leaf and capsule wall after recovering from HT contributed to an increased boll weight, which finally maintained cotton yield.

Novel intra-boll yield components and Q-score can further evaluate the effect of phosphorus fertilizer on cotton yield and fiber quality

Novel intra-boll yield component traits and fiber quality indices have been used by breeders to select suitable Gossypium hirsutum L. lines, but there is little research on how these traits change during cultivation practices, especially fertilizer application. We hypothesized that these novel traits have obvious responses to phosphorus (P) fertilizer, which would explain the variation in yield and fiber quality under different P conditions. To address this hypothesis, a field test was conducted with a low-P sensitive cotton cultivar (Lu 54) and a low-P tolerant cotton cultivar (Yuzaomian 9110) under different P fertilizer rates (0 as control, 100, and 200 kg P2O5 ha−1) from 2016 to 2018. The results showed that P fertilizer application (100, and 200 kg P2O5 ha−1) increased the lint yield, and bolls per ha contributed most to the increase in lint yield, followed by boll weight and lint percentage. The increased bolls per ha under P fertilizer application was due to the accelerated process of boll forming and the slowing of shedding process. The increased boll weight under P fertilizer application could be explained by the higher seed biomass per boll and fiber biomass per boll, especially the latter. The higher seed biomass per boll was due to the increased seeds per boll, and higher fiber biomass per boll should be attributed to the increased fibers per seed under P fertilizer application. The positive contribution of lint percentage to lint yield formation under P fertilizer application could be attributed to the increased fiber biomass per seed. P fertilizer application decreased fiber micronaire, indicating that fiber thickness was decreased by extra P fertilizer, which might be associated with the negative effects of increased fibers per seed and fiber density. In addition, P fertility application promoted the elongation of fiber cells and fiber length uniformity, and increased fiber strength. The end result was an increase in the comprehensive fiber quality index (Q-score) after P application. Moreover, compared to Yuzaomian 9110, yield traits including lint yield, bolls per ha, seeds per boll, seed index, and SSA, and quality indices including fiber length, fiber strength, and Q-score were more sensitive to P fertilizer application in Lu 54.

Late-planted short-season cotton without plastic mulching is an alternative to early-planted mulched full-season cotton

The early planting of full-season cotton (Gossypium hirsutum L.) at a moderate plant density under plastic mulching is a traditional means of growing cotton in the Yellow River valley of China. However, it is labor intensive, consumes a large amount of materials, and also results in residual plastic pollution in the soil. While our previous studies indicated that late planted short-season cotton under plastic mulching greatly reduces labor and material inputs and increases net revenue, the residual plastic pollution remains an issue. It is unclear if short-season cotton can be managed without yield loss in the absence of plastic mulching. A field experiment was therefore conducted using a random complete block design with four treatments, including the early planting of full-season cotton with (FCM) and without plastic mulching (FC), and the late planting of short-season cotton with (SCM) and without plastic mulching (SC), in the Yellow River valley from 2017 to 2019. The yield, yield components, input and output values, earliness, dynamics of flowering and boll setting, and late-season leaf senescence in cotton were examined. The results showed that early planted full-season cotton under mulching (FCM) produced a 21.1 and 20.4 % higher seedcotton yield and boll density, respectively, and improved earliness over the non-mulched treatment, while the boll weight did not differ significantly. Short-season cotton without plastic mulching produced comparable seedcotton yields to that with mulching (SCM), and there was no significant difference in average boll weight, boll density, or earliness between the mulching and non-mulching treatments. However, SC had a 7.0 and 12.1 % smaller boll density and boll weight, respectively, than FCM and thus produced a 17.9 % lower seedcotton yield. Therefore, SC produced 14.9 and 14.4 % greater net returns than SCM and FCM, respectively, because it consumed less labor and material inputs. Short-season cotton without plastic mulching delayed leaf senescence due to reduced boll load and thus increased boll weight in the late season compared with SCM. In addition, SC exhibited improved earliness as a result of a higher flowering rate, faster fruiting, and more concentrated boll opening than FCM. Short-season cotton without plastic mulching also avoided the residual film pollution in the soil. The overall results demonstrated that the late planting of short-season cotton without mulching is a promising alternative for sustainable cotton production in the Yellow River valley region of China as well as other cotton growing areas with similar ecology.

Effects of planting patterns on yield, quality, and defoliation in machine-harvested cotton

The aim of this study was to elucidate the effects of different machine-harvested cotton-planting patterns on defoliation, yield, and fiber quality in cotton and to provide support for improving the quality of machine-harvested cotton. In the 2015 and 2016 growing seasons, the Xinluzao 45 (XLZ45) and Xinluzao 62 (XLZ62) cultivars, which are primarily cultivated in northern Xinjiang, were used as study materials. Conventional wide-narrow row (WNR), wide and ultra-narrow row (UNR), wide-row spacing with high density (HWR), and wide-row spacing with low density (LWR) planting patterns were used to assess the effects of planting patterns on defoliation, yield, and fiber quality. Compared with WNR, the seed cotton yields were significantly decreased by 2.06–5.48% for UNR and by 2.50–6.99% for LWR, respectively. The main cause of reduced yield was a reduction in bolls per unit area. The variation in HWR yield was −1.07–1.07% with reduced bolls per unit area and increased boll weight, thus demonstrating stable production. In terms of fiber quality indicators, the planting patterns only showed significant effects on the micronaire value, with wide-row spacing patterns showing an increase in the micronaire values. The defoliation and boll-opening results showed that the number of leaves and dried leaves in HWR was the lowest among the four planting patterns. Prior to the application of defoliating agent and before machine-harvesting, the numbers of leaves per individual plant in HWR were decreased by 14.45 and 25.00% on average, respectively, compared with WNR, while the number of leaves per unit area was decreased by 27.44 and 36.21% on average, respectively. The rates of boll-opening and defoliation in HWR were the highest. Specifically, the boll-opening rate before defoliation and machine-harvesting in HWR was 44.54 and 5.94% higher on average than in WNR, while the defoliation rate prior to machine-harvesting was 3.45% higher on average than in WNR. The numbers of ineffective defoliated leaves and leaf trash in HWR were the lowest, decreased by 33.40 and 32.43%, respectively, compared with WNR. In conclusion, the HWR planting pattern is associated with a high and stable yield, does not affect fiber quality, promotes early maturation, and can effectively decrease the amount of leaf trash in machine-picked seed cotton, and thus its use is able to improve the quality of machine-harvested cotton.

Effect of Foliar Application with Bentonite on Growth and Productivity of Egyptian Cotton

Effect of Foliar Application with Bentonite on Growth and Productivity of Egyptian Cotton

Response of Cotton Plant to Foliar Application with Mepiquat Chloride (Pix) and Kaolin

One field experiment was carried out on clay soil in 2016 season and repeated in 2017 season in El-Gemmeiza Agricultural Research Station, Agricultural Research Center, El-Gharbiya Governorate, Egypt, to study the effect of seven treatments including foliar application with two rates of mepiquat chloride (pix); 2 and 3cm3/L, two rates of Kaolin (2 and 3g/L), two rates of mepiquat chloride(pix) and Kaolin application in combination (2cm3+2g)/L, (3cm3+3g)/Lthree times (at squaring stage, at the start of flowering and at the top of flowering) and control treatment on leaf chemical composition, plant growth, earliness, fiber quality and yield of Egyptian cotton (Gossypium barbadense L.), Giza 86 cultivar. A randomized complete blocks design with 3 replicates was used in both seasons. The important results could be summarized as follow:- The tested treatments had a significant effect on leaves N, P, K, chlorophyll a, b, total chlorophyll and carotenoids contents in the two seasons of study, where foliar application with mepiquat chloride at 3cm3/L in combined with kaolin at 3g/L three times recorded the highest values of these traits in both seasons followed by foliar application with mepiquat chloride alone at 3cm3/L. While, the control treatment produced the lowest values of these traits.Foliar spraying with mepiquat chloride at 3cm3/L in combined with kaolin at 3g/L three times significantly reduced final plant height, followed by foliar application with mepiquat chloride at 3cm3/L three times, foliar application with mepiquat chloride at 2cm3/L in combined with kaolin at 2g/L three times, foliar application with mepiquat chloride at 2cm3/L, foliar application with kaolin at 3g/L three times and foliar application with kaolin at 2g/L three times, while control treatment recorded the tallest plants. Number of fruiting branches/plant did not affect by these treatments. Foliar spraying with mepiquat chloride at 3cm3/L in combined with kaolin at 3g/L three times significantly increased numbers of total flowers and total bolls set/plant, boll setting and earliness percentages followed by foliar application with mepiquat chloride at 3cm3/L. But, the lowest values were obtained from the control treatment.Foliar spraying with mepiquat chloride at 3cm3/L in combined with kaolin at 3g/L three times significantly increased boll weight, number of open bolls/plant, seed cotton yield/plant, seed index and seed cotton yield/fed in the two seasons of study followed by foliar application with mepiquat chloride at 3cm3/L. But, untreated plants produced the lowest values.On the other hand, the tested treatments had insignificant effect on fiber quality (fiber strength and micronaire reading) and lint percentage in both seasons.This study demonstrates that foliar spraying with mepiquat chloride (pix) at 3cm3/L in combined with kaolin at 3g/L three times (at squaring stage, at the start of flowering and at the top of flowering) could be recommended to improve the chemical composition of leaves, vegetative growth traits, earliness, yield/feddan, yield components and fiber quality of Giza 86 cotton cultivar under conditions of El-Gemmeiza location.

Yield components and quality of intercropped cotton in response to mepiquat chloride and plant density

Cotton yield is greatly improved by moderately increasing plant density and modifying the cotton plants to have a compact structure, which is also required by the increasing demand for mechanized harvest. However, in cotton strip intercropped with wheat, only limited knowledge on yield response to plant density and plant growth regulator i.e. mepiquat chloride (MC) exists. Here we quantified MC and plant density effects on cotton yield components and quality in wheat–cotton relay intercropping by three field experiments in 2010–2012 in Anyang, China. Four plant densities and four MC treatments were applied in different times and dosages. Lint yield significantly increased 40.7% when plant density increased from 3.0 to 7.5plantsm−2, and enhanced 7.9% by applying MC four times compared to MC free control. High densities increased the number of bolls per m2 but decreased single boll weight. Conversely, applying MC generally slightly decreased number of bolls, with the exception of a significant increase by applying MC four times, and increased boll weight. Lint percentage was decreased by applying MC. The yearly climate significantly impacted the effects of applying MC and plant density. Application of MC did not significantly affect cotton fiber length and micronaire, but increased fiber strength. Applying MC in combination with increasing plant density led to harvestable bolls to be located more at low and middle positions on the plant. The increase of boll weight by applying MC was partly resulted from the optimal distribution of harvestable bolls within the canopy. The results help farmers to optimize plant density and MC application in the intercropped cotton.

Effect of 1-MCP on Boll Development and Subtending Leaves of Cotton (<i>Gossypium hirsutum</i> L.) Plants

Ethylene regulates multiple physiological processes in cotton (Gossypium hirsutum L.) ranging from square and boll abscission to senescence. This field study investigated the effect of an ethylene inhibiting compound 1-methylcyclopropene (1-MCP) on boll development and the corresponding subtending leaves. The study was conducted in 2011 and 2012 at the Texas A & M Agri-LIFE Research Farm in Burleson County, TX. The study consisted of two rates of 1-MCP (0 and 10 g a.i. ha-1) applied at one and two weeks after first flower. Boll development and subtending leaves were studied on the tagged flowers during the growing season. 1-MCP treatment increased cotton boll weight at 20 days after flowering. This study showed that 1-MCP-treated subtending leaves exhibited decreased membrane damage and lipid peroxidation, and higher chlorophyll content and photosynthetic efficiency at 20 to 30 days after flowering. The healthier state of subtending leaves should have provided more carbohydrates for the fruits which could partially explain the reason for the increased boll weight. However, this beneficial effect of 1-MCP did not last to the end of the growing season and failed to result in a yield increase ultimately. Multiple applications or extending effective duration of 1-MCP is desirable to enhance the activity of 1-MCP to make a significant difference in cotton yield.

Boron Requirement of Irrigated Cotton in a Typic Haplocambid for Optimum Productivity and Seed Composition

Boron (B) deficiency hampers cotton (Gossypium hirsutum L.) growth and productivity globally, especially in calcareous soils. The crop is known as a heavy feeder of B; however, its reported plant analysis diagnostic norms for B-deficiency diagnosis vary drastically. In a 2-year field experiment on a B-deficient [hydrochloric acid (HCl)–extractable 0.47 mg B kg−1], calcareous, Typic Haplocambid, we studied the impact of soil-applied B on cotton (cv. CIM-473) growth, productivity, plant tissue B concentration, and seed oil composition. Boron was applied at 0.0, 1.0, 1.5, 2.0, 2.5, and 3.0 kg B ha−1, as borax (Na2B4O7·10H2O), in a randomized complete block design with four replications, along with recommended rates of nitrogen (N), phosphorus (P), potassium (K), and zinc (Zn). Boron use improved crop growth, decreased fruit shedding, and increased boll weight, leading to seed cotton yield increases up to 14.7% (P < 0.05). Improved B nutrition of plants also enhanced seed oil content (P < 0.05) and increased seed protein content (P < 0.05). Fiber quality was not affected. Fertilizer B use was highly cost-effective, with a value–cost ratio of 12.3:1 at 1 kg B ha−1. Fertilizer B requirement for near-maximum (95% of maximum) seed cotton yield was 1.1 kg B ha−1 and HCl-extractable soil B requirement for was 0.52 kg ha−1. Leaf tissue B requirement varied with leaf age as well as with plant age. In 30-day plants (i.e., at squaring), B-deficiency diagnosis critical level was 45.0 mg kg−1 in recently matured leaves and 38.0 mg kg−1 in youngest open leaves; at 60 days old (i.e., at flowering), critical concentration was 55.0 mg kg−1 in mature leaves and 43.0 mg kg−1 in youngest leaves. With advancement in plant age critical B concentration decreased in both leaf tissues; that is, in 90-day-old plants (i.e., at boll formation) it was 43.0 mg kg−1 in mature leaves and 35.0 mg kg−1 in the youngest leaves. As critical concentration range was narrower in youngest leaves (i.e., 35–43 mg kg−1) compared with mature leaves (i.e., 43–55 mg kg−1), B concentration in youngest leaves is considered a better indicator for deficiency diagnosis.

Effect of 6-BA and ABA Applications on Yield, Quality and Photosynthate Contents in the Subtending Leaf of Cotton with Different Planting Dates

To study the effects of 6-BA and ABA applications on carbohydrate contents and endogenous hormones in subtending leaf, and their relationship to cotton yield and quality under different planting dates, we conducted a field experiment with two cotton cultivars Kemian 1 and NuCOTN 33B in the Lower Reaches of Yangtze River (Nanjing) and in the Yellow River Valley (Anyang), China. The cotton seeds were planted on Apr. 25th and May 25th, 2006, respectively, which could result in different growth temperatures for the bolls and their subtending leaves at the same site, and the growth regulators were sprayed at flowering stage. The results showed that the application of 6-BA significantly increased contents of sucrose and starch, and sucrose transformation rate in the subtending leaf, while the application of ABA only regulated the balance of endogenous hormones. The application of 6-BA increased boll weight and enhanced fiber qualities in cotton plants with planting dates of Apr. 25th and May 25th, whereas the decrease ranges of cotton yield and quality in Anyang were less for the application of ABA in cotton plants with planting date of May 25th, compared to those with planting date of Apr. 25th. However, the seed quality was not affected by the applications of 6-BA or ABA significantly. The application of 6-BA or ABA improved relative cotton quality of late planted cotton, whereas the action mechanisms were different. The application of 6-BA improved cotton yield and quality via enhancing the photosynthate contents and sucrose transformation rate. However, the application of ABA improved cotton yield and quality via in- creasing the stress resistance of cotton plants.

Yield, development and quality response of dual-toxin Bt-cotton to manual simulation of damage by Helicoverpa spp. in Australia

Larvae of Helicoverpa spp. can occasionally be found in Bollgard II® cotton (Gossypium hirsutum L.), raising concerns about the validity of current thresholds for their control. Experiments were conducted in two seasons to test these thresholds using artificial damage to different fruiting structures (squares or bolls or both) at three stages of cotton growth. At early flowering, Bollgard II® cotton plants tolerated 100% square removal from all plants without significant yield loss, indicating substantial compensation primarily through increased survival of subsequently produced fruit. This delay in the fruiting cycle, however, resulted in maturity delays of up to 6–13 d. At peak flowering, only 100% square removal or the combination of 30% boll damage and 100% square removal caused significant yield loss. Compensation in other treatments was primarily through increased boll weight. Square removal or square removal plus boll damage significantly delayed cotton maturity by about 5 d, but boll damage alone did not. At late flowering, the heaviest damage treatments (30% bolls damaged across 50% or all plants) significantly reduced yield, and there was a trend toward lower yield as damage increased, suggesting limited compensation. Boll damage had no effect on cotton maturation at late flowering. Damage distribution (all or half of the plants damaged) affected yield proportional to the amount of damage inflicted. Across all times and treatments, fiber quality was never affected to a degree that incurred price penalties commercially. In commercial fields, we rarely encountered damage levels equivalent to the heavier damage treatments, suggesting that current thresholds are adequate.

Boll Retention and Boll Size among Intrasympodial Fruiting Sites in Cotton

Competition among cotton (Gossypium hirsutum L.) bolls for assimilates may affect boll retention and size, making it an important factor affecting productivity. A 4‐yr field study was conducted on Commerce silt loam to evaluate relationships among fruiting sites (FS) on sympodial branches of cotton receiving preplant fertilizer N rates of 0, 28, 56, 84, 112, 140, or 168 kg ha−1 or a preplant + sidedress application of 56 + 56 kg ha−1 each year. For each FS on each sympodium, there were four possible competition levels based on boll retention or abscission at FS 1, 2, and 3. Competition levels were determined by natural retention or abscission of fruit. Boll retention and weight were influenced by competition level, year, sympodia, FS location on the sympodia and by N rate. Competition effects on boll retention were affected by N rate but not by sympodia. Conversely, competition effects on boll weight were not affected by N rate but were affected by sympodia. Boll weight at FS 1 increased when bolls were retained at FS 2 and 3. Retention of a boll at FS 1 increased boll retention at FS 2 but decreased boll weight at FS 2. In contrast, boll weight at FS 2 increased when bolls were retained at FS 3, or at FS 1 and 3. Fertilizer N increased boll weight at FS 2, except when a competing boll was present at FS 1. Apparent increased competition among FS on a sympodium had favorable effects on boll retention and on boll weight except for FS 2 when FS 1 retained a boll and FS 3 did not retain a boll.

Response of Cotton, Gossypium hirsutum L., to Damage by Insect Pests in Australia: Manual Simulation of Damage

Three experiments were done between 1984 and 1987 in manually simulated pest damage with up to 14 damage treatments in any year, involving different types and levels of damage at three stages of the season applied to three varieties, two plant populations, and two irrigation regimes. In these experiments, the cotton plant has again shown a considerable ability to compensate in terms of total lint yield for early damage, involving either the loss of the growing point or squares. Although severe damage or combinations of tip and square removal sometimes caused considerable delay in maturity, light and moderate damage had little effect. Damage treatments did not affect fiber attributes sufficiently to have incurred price penalties commercially, despite extreme delay in some cases. Damage treatments did not interact with plant populations and irrigation regimes but the locally bred okra leaf variety ‘Siokra’ was more responsive to damage than the normal leaf variety ‘Deltapine 90’, with increased yield at light to moderate levels of early damage and decreased yield at severe levels. Evidence was found in the data from these experiments for the occurrence of three out of four previously identified physiological mechanisms involved in compensation by the crop plant for damage: damage substituting for physiological shedding, increased boll weight and increased rate of flowering. There was no evidence of the fourth mechanism, increased boll set.

Cotton Response to Planting Date and Mepiquat Chloride

AbstractFew studies have documented the effect of planting date on cotton (Gossypium hirsutum L.) response to mepiquat chloride (MC) (N,N‐dimethylpiperidinum chloride). Planting dates were mid‐April, early May, and mid‐May during 1982, 1983, and 1984, and consisted of five cultivars representing three general maturity types: early—‘DES 422’; intermediate—‘Coker 3131’, ‘Stoneville 825’, and ‘McNair 235’; and full season—‘Deltapine 90’. Mepiquat chloride was applied at a rate of 49 g a.i. ha−1 when the plants had about 0.7 white flowers per meter of row. More parameters were affected by chemical treatment and planting date than by cultivars. Plants were taller and produced fewer flowers, smaller bolls, and less lint as planting dates were delayed. In addition, most boll components were adversely affected by delayed planting dates. However, most of the adverse effects caused by delayed planting were mitigated by the MC treatment. Mepiquat chloride x planting date interactions occurred for plant height, flower production, lint yield, and seed index. Mepiquat chloride caused a 4.5% reduction in lint yield from the early planted plots, and 5.4 and 12.7% yield increases from the optimum and late plantings, respectively. Mepiquat chloride increased boll weight in all plantings, but affected (increased) flower production only in the late planting. Seed index was increased and lint percentage reduced in all MC‐treated plots from each of the three plantings. The MC early, intermediate‐, and late‐planting plots averaged 0.11, 0.25, and 0.30 less height, respectively, than the control plots. Statistical significance was achieved only for the latter two plantings. These studies indicate that MC application would be most beneficial in late‐planted cotton, which tends to produce more vegetative growth than earlier plantings.

Effects of fruiting form removal on cotton reproductive development

Short fiber cotton ( Gossypium hirsutum L.) was grown at 10 plants per m-row in 96-cm rows on high fertility soils with adequate irrigation. Small squares (floral buds), large squares or small bolls were removed from the cotton crop over various periods, and the subsequent crop response in terms of flowering, boll opening and seed cotton accumulation was followed. In general, removing larger fruiting bodies caused a greater reduction in open bolls than removing smaller fruiting bodies, where the timing of the treatments was comparable. For small square removal, earlier removal caused a greater reduction in open bolls than did later removal. However, the earlier treatments also began to compensate earlier for the effects of damage, and so did not in general have fewer open bolls at the final harvest date than the later treatments. A number of different mechanisms first reduced, and then compensated for, the effects of fruiting body removal on flowering, boll opening and yield. Natural shedding of squares and bolls appeared to be important in reducing the effects of fruiting body removal. The crop compensated for removal with an increased rate of flowering late in the season, increased percentage boll set, and increased boll weight. Not all treatments compensated in all these ways. Nevertheless, no treatment significantly reduced final yield.