Lint Yield Research Articles

Screening cotton cultivars under induced water-deficit stress in controlled environments and field settings: expression of drought tolerance traits

ABSTRACT Cotton (Gossypium hirsutum L.) is often grown in climates of intermittent drought conditions. Plants that limit transpiration rates (TRs) when initially exposed to water-deficit stress will preserve water for use later during critical growth stages. Two traits resulting in conservative TRs are TR limitations under soil drying and high vapor pressure deficit (VPD, >2.5 kPa). The objective of this study was to assess the performance of four contrasting cotton cultivars and their TRs under induced water stresses. Three studies were conducted to test (i) the early stomatal closure under soil drying in a greenhouse, (ii) the TR to varying VPD levels in a growth chamber, and (iii) the stomatal conductance (gs), wilting score, specific leaf area (SLA), relative water content (RWC), and yield in an extreme field environment. Significant differences in the fraction of transpirable soil water threshold (FTSW threshold) were detected among cultivars in the greenhouse. The FTSW threshold among cultivars ranged from 0.29 to 0.39. Under varying VPD levels, only PHY 400 W3FE expressed a limited TR (TRlim) with increasing VPD at 1.6 kPa. In the field study, differences in gs, wilting score, RWC, SLA, and lint yield were observed among cultivars within the water limited treatments (i.e. rainout and rainfed). PHY 400 W3FE had the lowest wilting score compared to other cultivars. Under the rainout treatment, PHY 400 W3FE yielded 37% higher than PHY 500 W3FE. Results indicate a trend in water saving potential among cotton cultivars, given the differences in their TR sensitivity to water-deficit stress conditions.

Impact of Growth Retardant and Defoliant on Morpho-physiological Traits and Yield Improvement in Cotton

In cotton, mechanized harvesting has gained popularity in recent years due to labor-intensive process and shortage of labor. Moreover, mechanized harvesting of cotton depends on plant morphological characters like plant height, internodal length and synchronized boll maturity and opening etc. Mechanized harvesting enhancing the harvesting efficiency of cotton which is achieved by the use of some chemicals to attain good lint yield and fibre quality. With this background, the field experiment was conducted to study the impact of growth retardant and defoliant on morpho-physiological traits and yield improvement in cotton (CO 17) during 2021-2022 by following randomized block design with four treatments and five replications. The current study revealed that spraying of 0.015% mepiquat chloride (MC) at square formation and boll development stage significantly reduced the leaf area, plant height, total dry weight and boll number when compared to control. However, chlorophyll content and normalized difference vegetation index (NDVI) were recorded higher in 0.015% mepiquat chloride (MC) applied treatments than control. Moreover, spraying of mepiquat chloride (0.015%) at square formation and boll development stage followed by spraying of 0.9% sodium chlorate (SC) at 60% boll bursting stage significantly increased the seed cotton yield compared to other treatments and recorded maximum seed cotton yield of 25.22% compared to control. Results clearly indicate that application of MC followed by SC could be a better practice for canopy management in cotton, resulting in improved efficiency of mechanical harvesting and good lint yield and fibre quality.

Growth, boll development, agronomic performance, and fiber quality of Gossypium barbadense L. in the southeastern U.S. Coastal Plain

AbstractPima (Gossypium barbadense L.) cotton is currently grown commercially in the western United States and has exceptional fiber quality, which provides an economic value almost two times greater than Upland (Gossypium hirsutum L.) cotton. Due to limited experience with Pima production in the southeastern United States, our primary objective was to compare the growth, development, agronomic performance, and fiber quality of four Pima genotypes with a high‐yielding high fiber quality commercial Upland cultivar under irrigated and dryland conditions at different planting dates. Lint yields of all Pima genotypes were ∼50% less and had lower lint percentages (38.0–42.4%) than the Upland genotype (45.7%); however, the Pima genotypes had consistently lower micronaire values and increased fiber strength, length, and uniformity. Although irrigation did not significantly impact agronomic and fiber quality performance, plants grown under supplemental irrigation developed 10% more bolls throughout the season, mostly occurring on monopodial branches and at mainstem nodal positions above 15. Bolls on Pima genotypes were 13–34% smaller than the Upland genotype and developed at more distal and higher nodal positions in the plant canopy. The highest net returns were found in 2019 at the early planting date, displaying the importance of timely planting of Pima genotypes when grown in the southeastern United States. Results suggest that irrigation may not be required for Pima production in the southeast, early planting is preferred to obtain maximum yields, and increasing lint percent, boll number, or earliness through breeding may improve Pima yields in the southeastern United States.

Comparative performance of hybrid generations reveals the potential application of F2 hybrids in upland cotton

BackgroundThe utilization of heterosis has greatly improved the productivity of cotton worldwide. However, a major constraint for the large-scale promotion of F1 hybrid cotton is artificial emasculation and pollination. This study proposed the potential utilization of F2 hybrids to improve upland cotton production through a comparative evaluation of hybrid generations.ResultsEight upland cotton varieties were analyzed and crosses were made according to NCII incomplete diallel cross-breeding design in two cotton belts of China. Variance analysis revealed significant differences in agronomic, yield, and fiber quality in both generations and environments. The broad-sense heritability of agronomic and yield traits was relatively higher than quality traits. Furthermore, the narrow-sense heritability of some traits was higher in F2 than in the F1 generation in both cotton belts. Overall, parental lines Zhong901, ZB, L28, and Z98 were observed with maximum combining ability while combinations with strong special combining ability were ZB × DT, L28 × Z98, and ZB × 851. The yield traits heterosis was predominant in both generations. However, the level of heterosis was altered with trait, hybrid combination, generation, and environment. Interestingly, L28 × Z98 performed outstandingly in Anyang. Its lint yield (LY) was 24.2% higher in F1 and 11.6% in F2 than that of the control Ruiza 816. The performance of SJ48 × Z98 was excellent in Aral which showed 36.5% higher LY in F1 and 10.9% in F2 than control CCRI 49. Further results revealed most hybrid combinations had shown a low level of heterosis for agronomic and fiber quality traits in both generations. Comparatively, ZB × DT and L28 × Z98 showed hybrid vigor for multiple traits in both generations and cotton belts. It is feasible to screen strong heterosis hybrid combinations with fine fiber in early generations. In the two environments, the correlation of some traits showed the same trend, and the correlation degree of Anyang site was higher than that of Aral site, and the correlation of some traits showed the opposite trend. According to the performance of strong heterosis hybrid combinations in different environments, the plant type, yield and fiber traits associated with them can be improved according to the correlation.ConclusionsThrough comparative analysis of variance, combining ability, and heterosis in F1 and F2 hybrids in different cotton belts, this study proposed the potential utilization of F2 hybrids to improve upland cotton productivity in China.

Predicting and interpreting cotton yield and its determinants under long-term conservation management practices using machine learning

Accurate predictions of crop yield are an integral part of effective agricultural tactical and strategic management decisions to sustain yield without adversely impacting the environment. Process-based simulation models are widely used to predict crop yields, but their application remains limited by the requirements of substantial expertise, intensive data, and extensive calibration. Therefore, greater attention is currently being devoted to machine learning (ML) methods that are more computationally expedient. We evaluated six ML algorithms (linear regression, ridge regression, lasso regression, random forest, XGboost, and artificial neural network (ANN)) to predict cotton (Gossypium spp.) yield and determine the yield response to critical determinants using long-term (1986–2018) data on management, climate, historical yield, and point measurement of soil organic carbon (SOC) from continuous no-till (NT) cotton cropping system in west Tennessee. Data from 1986 to 2015 were used for model training, hyper-parameterization and testing, while data from 2016 to 2018 were used for independent model validation. Results showed that tree-based models (random forest and XGboost) outperformed other models in predicting lint yield. The variable importance scores, predicted by random forest model, indicated that cotton yield was more responsive to management variables (nitrogen (N) fertilization rate, cover crop, and years since NT establishment) followed by soil (SOC) and climate variables at the study site. The model identified optimal N application at 60 kg ha-1N rate for cotton lint yield, and also highlighted that the benefits of NT in enhancing yield can be achieved after 15 years of practice. The model predicted that the long-term adoption of hairy vetch (Vicia villosa), a legume cover crop, has the potential to increase cotton yield. Among the climate variables, cotton lint yield was most impacted by average maximum temperature and precipitation during flowering to open boll period. While random forest and XGboost proved to be the most effective ML models in this study, multi-site data is needed to build a more robust model with greater generalization and interpretation capabilities under a wider prediction domain.

Foliar application of mepiquat chloride and nitrogen improves yield and fiber quality traits of cotton (Gossypium hirsutum L.).

Cotton (Gossypium hirsutum L.) is one of the most important cash crops primarily grown for fiber. It is a perennial crop with indeterminate growth pattern. Nitrogen (N) is extremely important for vegetative growth as balanced N-nutrition improves photosynthesis, resulting in better vegetative growth. Excessive N-supply results in more vegetative growth, which increases the incidence of insect pest and diseases’ infestation, pollute surface and ground water, delays maturity and produces low crop yield with poor quality. The use of plant growth regulators (PGRs) is an emerging option to control excessive vegetative growth. The PGRs help in improving plant architecture, boll retention, boll opening, yield and quality by altering growth and physiological processes such as photosynthesis, assimilate partitioning and nutrients dynamic inside the plant body. Mepiquat chloride (1,1-dimethylpiperidinum chloride) is globally used PGR for canopy development and control of excessive vegetative growth in cotton. This study investigated the effect of mepiquat chloride (MC) and N application on yield and yield components of transgenic cotton variety ‘BT-FSH-326’. Two N rates (0, 198 kg ha-1) and five MC rates (0, 30,60, 90 and 120 g ha-1) were included in the study. Results revealed that MC and N application improved boll weight, number of bolls per plant, and seed cotton and lint yields. The highest seed cotton and lint yields (3595 kg ha-1 and 1701 kg ha-1, respectively) were observed under foliar application of 198 kg ha-1 N and 120 g ha-1 MC. Fiber length, fiber strength, micronaire and uniformity were significantly improved with foliar application of MC and N. In conclusion, foliar application of MC and N could be helpful in improving yield and fiber quality of cotton.

Soil Water Dynamics and Cotton Production Following Cover Crop Use in a Semi-Arid Ecoregion

Conservation management practices such as no-tillage and cover crops can decrease soil’s susceptibility to wind erosion, but adoption of these practices has been limited on the Texas High Plains (THP) where producers are concerned with cover crop water usage. The objective of this study was to evaluate the impact of no-tillage and cover crops on cotton (Gossypium hirsutum L.) lint yield and soil water content in a deficit irrigated cropping system. Soil water was observed bi-weekly in long-term, continuous cotton systems established in 1998 that included (1) conventional tillage, winter fallow, (2) no-tillage with rye (Secale cereale L.) cover, and (3) no-tillage with mixed species cover located in Lamesa, TX, USA. Results include observations from 2018–2020 (years 21–23 of the study period). The adoption of conservation practices did not significantly reduce cotton lint yield compared to conventionally tilled, winter fallow cotton. Soil water was initially depleted with cover crops but was greater throughout the growing season following cover crop termination. Throughout the soil profile, water depletion and recharge were more dynamic with conservation practices compared to the conventionally tilled control. There were no differences in cotton water use efficiency between treatments. Results from this study indicate cover crop water usage is likely not the cause of cotton lint yield decline in this deficit irrigated semi-arid production system.

Barley Straw Combined with Urea and Controlled-Release Nitrogen Fertilizer Improves Lint Yield and Nitrogen Utilization of Field-Seeded Cotton

Straw returning is an important method of improving soil fertility and reducing environmental pollution. Controlled-release nitrogen fertilizer (CRN) is regarded as an effective way to reduce nitrogen (N) loss and increase N-use efficiency and crop yield. In order to determine the combined effects of straw management (straw removal and straw returning) and N-fertilization strategy (CK (no N), urea, CRN, and a mixture of urea and CRN (UC)) on lint yield, N utilization, and soil properties at harvest of field-seeded cotton, field experiments were conducted from 2018 to 2019. The results demonstrated that the lint yield was the highest with a combination of straw returning and UC, increasing by 4.2–46.9% over other combinations. Straw returning combined with UC facilitated biomass-accumulation and N-uptake from squaring to the boll-opening growth stage, contributing to higher N agronomic-use efficiency and apparent recovery-use efficiency. Moreover, regardless of the straw management, CRN or UC treatment increased the soil microbial N content and sucrase activity at harvest compared to urea or CK treatment. In summary, straw returning combined with UC was beneficial to the lint yield, N utilization, and soil N availability, which might be an optimizing strategy for field-seeded cotton.

Effect of Mepiquat Chloride on Phenology, Yield and Quality of Cotton as a Function of Application Time Using Different Sowing Techniques

Mepiquat chloride (MC) is a plant growth regulator used to manage the rampant vegetative growth of cotton. A two-year field experiment was conducted at the Postgraduate Agricultural Research Station, University of Agriculture, Faisalabad, Pakistan, during 2017 and 2018 to investigate the influence of MC applied at different times on phenology, morphology, lint yield and quality of cotton cultivated using different sowing techniques. MC was applied 50 days after sowing (DAS), 60 DAS and 70 DAS to cotton planted in flat fields (flat sowing), ridges (ridge sowing) and beds (bed sowing). The interactive effect of MC application time and sowing technique did not influence crop phenology, morphology, and lint yield and quality. It was revealed that the crop planted on beds took fewer days to flower (10%) as compared to that on the flat field, and the bed-sown crop produced a higher number of opened bolls (60%) and was characterized by a higher boll weight (32%) and seed cotton yield (50%) in comparison to the flat-sown crop. A late application of MC (at 70 DAS) caused a significant reduction in the time to flowering (8%), with a simultaneous increase in the number of opened bolls (60%), boll weight (32%), ginning out turn (8%) and lint yield (27%) as compared to MC application at 50 DAS. In terms of lint quality, cotton planted on beds had better fiber uniformity (8%) compared to that on the flat field, while MC applied at 70 DAS produced better fiber fineness by 27% in comparison to MC applied earlier. Overall, cotton planting on beds and MC application at 70 DAS may help improve cotton yield and fiber quality and may help in the mechanical picking of cotton.

Genomic prediction of cotton fibre quality and yield traits using Bayesian regression methods

Genomic selection or genomic prediction (GP) has increasingly become an important molecular breeding technology for crop improvement. GP aims to utilise genome-wide marker data to predict genomic breeding value for traits of economic importance. Though GP studies have been widely conducted in various crop species such as wheat and maize, its application in cotton, an essential renewable textile fibre crop, is still significantly underdeveloped. We aim to develop a new GP-based breeding system that can improve the efficiency of our cotton breeding program. This article presents a GP study on cotton fibre quality and yield traits using 1385 breeding lines from the Commonwealth Scientific and Industrial Research Organisation (CSIRO, Australia) cotton breeding program which were genotyped using a high-density SNP chip that generated 12,296 informative SNPs. The aim of this study was twofold: (1) to identify the models and data sources (i.e. genomic and pedigree) that produce the highest prediction accuracies; and (2) to assess the effectiveness of GP as a selection tool in the CSIRO cotton breeding program. The prediction analyses were conducted under various scenarios using different Bayesian predictive models. Results highlighted that the model combining genomic and pedigree information resulted in the best cross validated prediction accuracies: 0.76 for fibre length, 0.65 for fibre strength, and 0.64 for lint yield. Overall, this work represents the largest scale genomic selection studies based on cotton breeding trial data. Prediction accuracies reported in our study indicate the potential of GP as a breeding tool for cotton. The study highlighted the importance of incorporating pedigree and environmental factors in GP models to optimise the prediction performance.

Effects of cotton stubble return and subsoiling on dry matter accumulation, nutrient uptake, and yield of cotton in coastal saline-alkali soil

<p id="C3">To study the effects of cotton straw returning and deep loosening on cotton yield, salt content in 0-40 cm soil layer, dry matter accumulation dynamics, nitrogen (N), phosphorus (P), and potassium (K) accumulation, and distribution characteristics, four treatments including conventional tillage (CT), subsoiling tillage (ST), cotton stubble return (SR), and cotton stubble return + subsoiling tillage (SRT) were conducted using Lumianyan 36 as experimental material. The results showed that cotton stubble return increased cotton yield across two years. Lint yield of SR was 33.9% higher than CT, and SRT 32.1% higher than SR. Subsoiling increased cotton yield in 2017 and had no effect on it in 2018. Cotton stubble return reduced the salt content of 0-40 cm soil layer. The salt content of SR was 22.4% lower than that of CT, and the soil salt content of SRT was 20.7% lower than that of ST at the late growth stage in cotton. However, the effect of subsoiling on the salt content of 20-40 cm soil layer was inconsistent during the two-year experiment. The soil salt content of ST was 16.5% lower than of CT at late growth stage in 2017, but subsoiling had no effect on soil salt content in 2018. The accumulation dynamic of dry matter and N, P, K in cotton were consistent with the Logistic growth curve. Cotton stubble return increased maximal accumulation of dry matter and N, P, K in two years. The maximum accumulation of dry matter, N, P, and K in SR was 35.5%, 38.3%, 53.4%, and 55.0% higher than that in CT, and the accumulation of SRT was 27.0%, 30.7%, 21.2%, and 42.4% higher than that in ST. Compared with CT, the dry matter, N, P, and K accumulation of ST increased by 17.8%, 22.2%, 51.3%, and 40.6% in 2017, respectively, but had no effect in 2018. The dynamic of dry matter and nutrient accumulation were mainly affected by the maximum accumulation rate and rapid accumulation duration. Stubble return increased the amount and proportion of dry matter and N, P, K allocated to reproductive organs of cotton in the two-year experiment. Compared with CT, ST increased the allocation amount of dry matter and N, P, K to reproductive organs in 2017, but had no effect in 2018. In summary, the results revealed that cotton stubble return (SR) or cotton stubble return + subsoiling tillage (SRT) could be recommended tillage measures for soil improvement and high cotton yield in coastal saline-alkali cotton area.

Lint Yield Stability of Different Cotton (Gossypium barbadense L.) Genotypes Using GGE Biplot under Normal and Drought Irrigation Conditions

Lint Yield Stability of Different Cotton (Gossypium barbadense L.) Genotypes Using GGE Biplot under Normal and Drought Irrigation Conditions

Soil Available Phosphorus Deficiency Reduces Boll Biomass and Lint Yield by Affecting Sucrose Metabolism in Cotton-Boll Subtending Leaves

Soil available phosphorus (AP) deficiency and shortage of phosphate rocks limit cotton production in China. Therefore, pool-culture experiments were conducted in 2019 and 2020 using two cotton cultivars (CCRI-79, low-P tolerant; SCRC-28, low-P sensitive) under three soil AP levels (P0: 3 ± 0.5, P1: 6 ± 0.5, and P2 (control): 15 ± 0.5 mg kg−1) to ascertain the effect of soil AP on boll biomass and lint yield. P0 and P1 decreased the P concentration and net photosynthetic rate (Pn) of subtending leaves, thus, reducing boll biomass and lint yield. Additionally, soil AP deficiency decreased boll wall:boll, lint:boll, and lint:seed, and increased seed:boll ratio. Upper fruiting branch positions (FB9–12) had higher lint:seed ratio and proportion of the total lint yield under low soil AP. Moreover, soil AP deficiency also reduced the sucrose transformation rate (Tr) and activities of sucrose-metabolizing enzymes, such as ribulose-1,5-bisphosphate carboxylase-oxygenase (Rubisco), sucrose phosphate synthase (SPS), and sucrose synthase (SuSy), while increased carbohydrate levels (soluble sugar, sucrose, and starch) and the activity of cytosolic fructose-1,6-bisphosphatase (cy-FBPase) in the subtending leaves. The sucrose and starch contents, cy-FBPase, and SPS activities of SCRC-28 were more sensitive to low soil AP than CCRI-79. Higher Tr and activities of initial Rubisco and SuSy in the subtending leaves improved boll biomass and lint yield.

Analysis of climate variability and influence of climate variables on major crop yields in Nalgonda District of Telangana State, India

Climate change has become a major concern globally, demanding immediate attention and action. In view of the extreme climatic uncertainties, it is obvious that Indian agriculture is highly vulnerable to climate change as climate is the direct input for production. This scenario emphasizes the dire need to understand the patterns of climate change and thus prepare agricultural systems for future climatic uncertainties. Therefore, the present study was conferred to analyse the climatic variability of Nalgonda district in Telangana State, considering 30 years (1988 to 2017) of historical weather data pertaining to rainfall and temperature (maximum and minimum). Climatic variability of the district was systematically analysed using box-and-whisker plot, Coefficient of Variation (CV), and trend analysis. The association between climatic variables (rainfall, maximum and minimum temperatures) and the major Kharif crop yields was calculated using Pearson's correlation coefficient. The results revealed that the recent decade (2008-2017) had a stable increase in seasonal rainfall in almost all the months compared to the earlier two decades but with the least consistency in rainfall (CV 29.03 %) and higher fluctuations in the maximum temperature (CV 2.38%). September month had shown the higher risk of recording low rainfall conditions compared to July and August months in the district. The rice crop yields during the recent decade (2008-2017) were found to have significant positive and negative associations with the rainfall in September and October months, respectively. Similarly, the lint yields of cotton crops were found to have a significant negative association with the maximum temperatures of the October and November months of the district. The major finding of the study realized was that climate variability and change exist in Nalgonda district, and the climate variables had significant effects on the crop yields of the district.

Effect of Planting Cotton in Solid and Single-skip Row Configurations on Yield and Soil Water Use

Australian growers plant crops using different skip row configurations to minimize production risk in water-limiting environments. Previous studies have focused on comparing the effect of row configuration on crop yield, and information on soil water is still lacking. The objective of this study was to compare the water use, soil water extraction, and yield of dryland cotton (Gossypium hirsutum L.) planted using solid and single-skip row configurations. An experiment comparing two row configuration treatments (solid and single-skip) was conducted in a cotton field with heavy-clay soil in the sub-tropical climatic environment of Queensland, Australia, during 2007-2008. Water content in the soil profile was measured about weekly using the neutron probe method. Measurements were taken from three positions from the crop row: within a row (P1), between two rows (P2), and skip or planted row (P3). The soil water measurements indicated that, in general, the solid treatment tended to extract more water from shallower depths earlier in the growing season. The single-skip treatment resulted in taller plants, which extracted more water from deeper in the soil profile later in the season. For the entire season, however, both treatments used around the same amount of soil water (128 mm), suggesting that both treatments were water-limited and used all the water available to the crop. The 128 mm added to the seasonal rainfall of 271 mm allowed us to estimate the seasonal crop water use at about 399 mm, which was around half of the seasonal grass-reference evapotranspiration (ETo = 804 mm) for the site. The lint yield was statistically the same for both treatments, although the taller plants from the single-skip treatment tended to have a greater yield per plant (but not significantly different). The estimated water use efficiency (WUE) for the solid and single-skip configuration were 3.5 and 3.3 kg lint/ha/mm water use, respectively.

Matching of Soil Phosphorus Distribution and Root Distribution in Cotton Field Based on Diffusive Gradients in Thin-Films (DGT)

ABSTRACT This study aimed to optimize the period of drip phosphorus (P) fertilization to increase P migration distance in soil and content in cotton, so as to achieve the coordinated above and belowground growth of cotton plants. A field experiment was conducted to study soil P in response to P application by drip irrigation during different periods of cotton cultivation using diffusive gradients in thin films (DGT) in situ. The root length density, biomass, P content and lint yield of cotton were investigated. Compared with broadcast P fertilization before plowing, drip P fertilization after sowing significantly increased DGT-P and root length density in the top 0–15 cm soil layer, and significantly increased the biomass P content and lint yield of cotton, but reduced the root/shoot ratio. In addition, drip P fertilization at bud stage could also increase the DGT-P and root length density in the top 0–10 cm soil layer compared with the broadcast P fertilization treatment. Our results indicate that drip P fertilization after sowing is an effective method to expand the vertical migration of P in soil, increase the length, density, and P content of shoot, and improve the growth of cotton.

Improving nitrogen use efficiency in irrigated cotton production

Irrigated cotton in Australia is mainly grown on heavy textured soils which are prone to waterlogging, resulting in significant losses of nitrogen (N) via denitrification and surface run-off. This study investigated fertiliser nitrogen use efficiency (fNUE) over three seasons on five commercial cotton farms using the 15N tracer technique. Fertiliser NUE was consistently low across all fertilised treatments, with on average 47% of the applied fertiliser lost and only 17% of the N taken up by the crop derived from fertiliser. There was no significant effect of different N fertiliser products and rates on cotton lint yield. High lint yields (0.9–3.6 Mg ha−1) could be achieved even without the application of N fertiliser, demonstrating mineralisation of soil organic N, residual fertiliser, or N returned with crop residues, as key source of N in these cropping systems. Using the nitrification inhibitor DMPP and overhead instead of furrow irrigation showed potential to reduce N fertiliser losses. The results demonstrate that under current on-farm management fNUE is low on irrigated cotton farms in Australia and highlight the need to account for soil N stocks and mineralisation rates when assessing optimized fertiliser rates. There is substantial scope to improve fNUE and reduce N losses without any impact on lint yield, by adjusting N fertiliser application rates, in particular in combination with the use of the nitrification inhibitor DMPP. Using overhead instead of furrow irrigation is a promising approach to improve not only water use efficiency, but also fNUE in irrigated cotton systems.

Effects of Plant Density, Mepiquat Chloride, Early-Season Nitrogen and Water Applications on Yield and Crop Maturity of Ultra-Narrow Cotton

Research investigating row spacing in high-yielding, high-input cotton (Gossypium hirsutum L.) production systems has found higher lint yields but no maturity benefits using high plant density, 25 cm spaced ultra-narrow rows (UNR). Seven experiments comparing 38 cm UNR and conventionally spaced rows (100 cm) were conducted over three years to determine if changes in plant density or management could optimize yield and maturity in a high-input UNR cotton production system. Two of these experiments compared 25, 38 and 100 cm spaced rows under different intra-row plant density (12 to 36 plants m−2). Three experiments managed 38 cm UNR and 100 cm spaced rows separately and one had extra early application of nitrogen and water. Across the seven experiments there were no differences in lint yield or crop maturity for 38 cm UNR compared to conventionally spaced rows. The only significant response to changes in inter- or intra-row density or agronomic management was an 18% increase in handpicked lint yield in the 12 plants m−2 38 cm UNR treatment compared to the same plant density in 100 cm spaced rows in one of the two experiments. This stability of yield response across row spacings indicates that there is an opportunity to reduce seed rates whilst maintaining yields in high-input UNR systems. UNR cotton did not require any difference in mepiquat chloride or nitrogen management compared with conventionally spaced cotton, nor did extra early inputs of nitrogen or water, and we concluded that is likely that the current recommendations for mepiquat chloride or nitrogen nutrition in conventionally spaced systems are appropriate for managing high-input UNR cotton crops.

Effect of inorganic and organic sources and levels of boron on growth, yield and quality of cotton (Gossypium hirsutum) under salt stress condition

Therefore, a simple, completely factorial randomized pot experiment was conducted during 2018 at pot culture yard, Department of Soil Science and Agricultural Chemistry, Annamalai University to evaluate the effect of organic and inorganic sources and levels of boron on growth and yield, quality attributes and uptake by cotton under salt stress condition. The experiment was conducted with four levels of boron (0, 0.5, 1.0 and 1.5 mg//kg of soil) through three sources viz., borox, solubar and magnesium borohumate complexes. The cotton variety LRA5166 was used as test variety. The results revealed that application of 1.5 kg of B through magnesium borohumate (MBH) complex recorded the higher plant height (124.6 cm), leaf area index (4.82), DMP (216 g/pot), yield components like number of bolls per plant (18.20), and mean boll weight (3.92) of cotton in saline sodic soil. Furthermore, higher seed cotton yield (93.51 g/pot), seed yield (54.72 g/pot) and lint yield (33.53 72 g/pot) were also recorded. This was on par with application of 1.0 kg of B through magnesium borohumate and recorded the plant height (122.81 cm), leaf area index (4.7), DMP (213 g/pot), yield components like number of bolls per plant (17.4), and mean boll weight (3.83 g), seed cotton yield (92.71 g/pot), seed yield (54.1 g/pot) and lint yield (32.96 g/pot) and followed by S2L4 (1.5 kg of B through solubar). The conclusion made from this study is the application of boron through 1.0 kg of B through magnesium borohumate will sustainably increase the cotton yield in saline sodic soil.

Sap velocity, transpiration and water use efficiency of drip-irrigated cotton in response to chemical topping and row spacing

Directly measuring plant transpiration of field crops and determining water use efficiency are difficult but essential to understand plant-water relations. In this study, we aimed to quantify plant transpiration and water use efficiency at diurnal and daily bases using sap flow measurements in cotton growing under plastic film cover and drip irrigation in relation to row configurations and chemical topping. Field experiment was carried out in 2020–2021 in Xinjiang, China. The experiment included two topping treatments: chemical topping using heavy amount of mepiquat chloride and traditional manual topping; and two typical row spacing for machine-harvesting: equal row spacing (76 cm) and narrow-wide row spacing (10 cm + 66 cm). Sap flow was measured using a heat ratio method after cotton first flowering stage and then calculated to transpiration per plant and per unit ground area. Chemical topping increased cotton plant height by 12%, leaf area index by 13%, and stem diameter by 9% but did not affect cotton lint yield compared with manual topping across two years and row configurations. The sap velocity of drip-irrigated cotton ranged overall from 20 to 45 cm hr−1 at the daytime and close to zero at nighttime. Across two years, the daily transpiration in chemical topping after flowering was 5.57 mm d−1 and 14.8% higher than in manual topping. That in narrow-wide row spacing was higher than in equal rows. However, the water use efficiency did not differ between topping and row spacing treatments, being 5.64 kg m−3 on average for aboveground dry matter. This knowledge would be useful to optimize cotton irrigation managements and to improve crop models by knowing exact plant transpiration at both plant and system levels.