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When comparing soil potassium (K) levels common in West Texas to the current Mehlich III-K critical levels for cotton (Gossypium hirsutum L.), fertilizer K applications are seldom recommended. However, when soil K is applied, positive responses in cotton yield have been reported. Studies were conducted in Lamesa and New Deal, TX to: 1) determine K effects on leaf K concentrations; 2) evaluate whether K application increases crop growth, yield, and fiber quality in sufficient K soils; and 3) evaluate whether K application under water deficit conditions also increases growth, yield, and fiber quality. In Lamesa, muriate of potash (KCl) was applied using two methods, knife-injected (0-0-15) and broadcast (0-0-60); and at New Deal, KCl was applied using knife injection. Potassium application rates included 0, 45, 90, 135, and 180 kg ha-1 with both high (90% ET) and low (30% ET) irrigation levels. At Lamesa in 2016 at 90% ET irrigation, lint yield was greater when 90 kg K ha-1 was broadcast (2,153 kg ha-1 lint) compared to the 180 kg K ha-1 treatment, and all K treatments with 30% ET irrigation. There were no lint yield differences in 2017 at Lamesa. At New Deal, lint yield was similar amongst all K application rates in both years. Although K application increased yield with the 90% ET irrigation level with broadcast application, no differences were observed in water-deficit cotton suggesting further research is needed to better understand the dynamics of K on lint yield in semiarid cotton production systems.

Water scarcity is increasing in the world, which is limiting crop production, especially in water-limited areas such as Southern High Plains of the United States. There is a need to adopt the irrigation management practices that can help to conserve water and sustain crop production in such water-limited areas. A 2-year field study was conducted during the summers of 2019 and 2020 to evaluate the effect of deficit irrigation levels and cultivars on root distribution pattern, soil water depletion, and water use efficiency (WUE) of cucumber (Cucumis sativus). The experiment was conducted in a split-plot design with four irrigation levels [100%, 80%, 60%, and 40% crop evapotranspiration (ETc)] as main plot factor and two cultivars (Poinsett 76 and Marketmore 76) as subplot factor with three replications. Results showed that root length density (RLD) was unaffected by the irrigation levels in 2019. In 2020, the RLD was comparable between 100% and 80% ETc, and it was significantly higher in 100% ETc than both 60% Eand 40% ETc. Root surface area density (RSAD) was not significantly different between 100% and 80% ETc, and it was significantly lower in both 60% and 40% ETc than 100% ETc in both years. Soil water depletion was the highest in 40% ETc followed by 60% and 80% ETc, and it was least in 100% ETc in both years. Evapotranspiration (ET) was the highest in 100% ETc followed by 80%, 60%, and 40% ETc. The WUE was not statistically different among the irrigation treatments. However, numerically, WUE was observed in the following order: 80% ETc > 100% ETc > 60% ETc > 40% ETc. The RLD, RSAD, soil water depletion, and ET were not significantly different between ‘Poinsett 76’ and ‘Marketmore 76’. However, fruit yield was significantly higher in ‘Poinsett 76’ than ‘Marketmore 76’, which resulted in higher WUE in Poinsett 76. It can be concluded that 80% ETc and Poinsett 76 cultivar can be adopted for higher crop water productivity and successful cucumber production in SHP.

Summary Abiotic stresses such as extreme temperatures, water‐deficit and salinity negatively affect plant growth and development, and cause significant yield losses. It was previously shown that co‐overexpression of the Arabidopsis vacuolar pyrophosphatase gene AVP1 and the rice SUMO E3 ligase gene OsSIZ1 in Arabidopsis significantly increased tolerance to multiple abiotic stresses and led to increased seed yield for plants grown under single or multiple abiotic stress conditions. It was hypothesized that there might be synergistic effects between AVP1 overexpression and OsSIZ1 overexpression, which could lead to substantially increased yields if these two genes are co‐overexpressed in real crops. To test this hypothesis, AVP1 and OsSIZ1 were co‐overexpressed in cotton, and the impact of OsSIZ1/AVP1 co‐overexpression on cotton's performance under normal growth and multiple stress conditions were analysed. It was found that OsSIZ1/AVP1 co‐overexpressing plants performed significantly better than AVP1‐overexpressing, OsSIZ1‐overexpressing and wild‐type cotton plants under single, as well as under multiple stress conditions in laboratory and field conditions. Two field studies showed that OsSIZ1/AVP1 co‐overexpressing plants produced 133% and 81% more fibre than wild‐type cotton in the dryland conditions of West Texas. This research illustrates that co‐overexpression of AVP1 and OsSIZ1 is a viable strategy for engineering abiotic stress‐tolerant crops and could substantially improve crop yields in low input or marginal environments, providing a solution for food security for countries in arid and semiarid regions of the world.

In Texas, mesquite and yellow-bluestem invasions are widespread. Identifying and monitoring juvenile and adult plants using high-resolution imagery from airborne sensors while they colonize new areas across the landscape can help land managers prioritize locations for treatment and eradication. In this study, we evaluated how data collection design using an unmanned aerial system (UAS) can affect plant detection and mapping. We used a Phantom 3 Professional unmanned aerial vehicle with a Parrot Sequoia multispectral camera for detecting and mapping native honey mesquite (Prosopis glandulosa) and non-native yellow bluestem (Bothriochloa ischaemum) at a rangeland site in northwest Texas. Flights were conducted seasonally during the period from summer 2017 to fall 2018 to test the seasonal impact of detecting plant species. Flights were conducted at altitudes of 30, 60, and 100 m, and four image classification techniques were tested to determine their viability of detecting distinct plant species. Results suggest that flights at 100-m aircraft altitude during the spring season are more effective (>80% user accuracies) for mapping mesquite canopies based on reflectance values and image segmentation information. Yellow bluestem mapping accuracies were low (

Since the release of dicamba-tolerant cotton in 2016, preplant and POST applications of dicamba to control glyphosate-resistant Palmer amaranth have increased. With the increase in area treated with dicamba, the risk of off-target movement to nontarget crops has increased. A field study was conducted at the Texas Tech University New Deal Research Farm equipped with subsurface drip irrigation in 2017 and 2018 to evaluate non-dicamba tolerant cotton response to dicamba when applied at four crop growth stages [first square (FS) + 2 wk, first bloom (FB), FB + 2 wk, and FB + 5 wk]. Dicamba at 0.56 (1×), 0.056 (1/10×), 0.0112 (1/50×), 0.0056 (1/100×), and 0.00112 (1/500×) kg ae ha–1 was applied to ‘FM 1830GLT’ cotton. When applications were made at FS + 2 wk, a shift in boll nodal position was apparent following dicamba at the 1/50× rate in 2017 and at 1/10× in 2018 compared to the nontreated control (NTC). A shift in boll distribution from the 1/50× rate of dicamba was apparent at FB in 2017, but not in 2018. Dicamba applied at the 1× rate at FB + 2 wk resulted in reduced boll numbers. No change in boll number or boll position was apparent following any dicamba rate when applied at FB + 5 wk in both years. Dicamba applied at 1/500×, 1/100×, and 1/50× rates at all timings did not affect yield relative to the NTC. When dicamba was applied at the 1/10× rate, the greatest yield loss was observed at FS + 2 wk followed by FB and FB + 2 wk. Micronaire increased following dicamba applied at 1/10× at FS + 2 wk, FB, and FB + 2 wk in 2017. In 2018, micronaire decreased following dicamba applied at 1/10× at FB + 5 wk.Nomenclature: Dicamba; Palmer amaranth, Amaranthus palmeri S. Wats; cotton, Gossypium hirsutum L.

The ratio of Na+ and K+ is an important determinant of the magnitude of Na+ toxicity and osmotic stress in plant cells. Traditional analytical approaches involve destructive tissue sampling and chemical analysis, where real-time observation of spatio-temporal experiments across genetic or breeding populations is unrealistic. Such an approach can also be very inaccurate and prone to erroneous biological interpretation. Analysis by Hyperspectral Imaging (HSI) is an emerging non-destructive alternative for tracking plant nutrient status in a time-course with higher accuracy and reduced cost for chemical analysis. In this study, the feasibility and predictive power of HSI-based approach for spatio-temporal tracking of Na+ and K+ levels in tissue samples was explored using a panel recombinant inbred line (RIL) of rice (Oryza sativa L.; salt-sensitive IR29 x salt-tolerant Pokkali) with differential activities of the Na+ exclusion mechanism conferred by the SalTol QTL. In this panel of RILs the spectrum of salinity tolerance was represented by FL499 (super-sensitive), FL454 (sensitive), FL478 (tolerant), and FL510 (super-tolerant). Whole-plant image processing pipeline was optimized to generate HSI spectra during salinity stress at EC = 9 dS m-1. Spectral data was used to create models for Na+ and K+ prediction by partial least squares regression (PLSR). Three datasets, i.e., mean image pixel spectra, smoothened version of mean image pixel spectra, and wavelength bands, with wide differences in intensity between control and salinity facilitated the prediction models with high R2. The smoothened and filtered datasets showed significant improvements over the mean image pixel dataset. However, model prediction was not fully consistent with the empirical data. While the outcome of modeling-based prediction showed a great potential for improving the throughput capacity for salinity stress phenotyping, additional technical refinements including tissue-specific measurements is necessary to maximize the accuracy of prediction models.

Increased water scarcity necessitates the implementation of water-conserving irrigation management practices to sustain crop production,especially in water-limited areas. A two-year field study was conducted during 2019 and 2020 to evaluate the effect of deficit irrigation on physiology, plant growth, and yield of cucumber cultivars. The experiment was conducted in a split-plot design with four irrigation levels (100% ETc (crop evapotranspiration), 80% ETc, 60% ETc, and 40% ETc) as main plot factor and two cultivars (Poinsett 76 and Marketmore 76) as subplot factor with three replications. Results showed that stomatal conductance (gs), transpiration rate (E), photosynthesis rate (Pn), intercellular CO2 concentration (Ci), and leaf area were significantly lower in 60% ETc and 40% ETc compared to 100% ETc while stomatal limitations, intrinsic water use efficiency (WUEi), and relative leaf temperature were significantly higher in 60% ETc and 40% ETc compared to 100% ETc. The observed values of these aforementioned parameters were comparable between 100% ETc and 80% ETc. A decrease in leaf area, as well as a decrease in Pn, resulted in a decline in overall photosynthesis per plant in 60% ETc and 40% ETc compared to 100% ETc. As a consequence of this, plant dry biomass and total fruit yield were significantly lower in 60% ETc and 40% ETc compared to 100% ETc. However, photosynthesis per plant was comparable between 100% ETc and 80% ETc due to comparable Pn and leaf area between them. Because of comparable photosynthesis per plant, plant dry biomass and fruit yield were comparable between 100% ETc and 80% ETc. Marketmore 76 had significantly higher gs, E, Pn, Ci, and leaf area and it had significantly lower stomatal limitations, WUEi, and relative leaf temperature than Poinsett 76. Vegetative dry biomass and total above-ground dry biomass were higher in Marketmore 76 but fruit yield was higher in Poinsett 76. These results suggest that 80% ETc irrigation level and Poinsett 76 cultivar can be recommended for successful cucumber production without causing a significant decline in fruit yield in water-limited Southern High Plains of United States.

No-tillage has been used for mitigating wind erosion on the Southern High Plains US for decades. This study investigated the effects of tillage and nitrogen (N) fertilizer timing on cotton lint yield, fiber quality, and seed N content during a three-year transition from conventional tillage (CT) to a no-tillage system both with a wheat (Triticum aestivum) cover crop (NTW) and without a cover crop (NT). Lint yield was different between tillage systems within each year with the NTW system producing greater lint yield than the CT system in the second and third year of the transition period. The concentration of cotton seed N was not different within years, although it was decreased in the no N added control in the third year. Cotton fiber strength was increased in the NTW system compared to the CT system in the second year of the study. However, the CT system produced increased fiber strength compared to the other two systems in 2018 and is likely the result of late-season weather conditions. It was determined that implementing a NTW system may increase lint yield within the first few years and has no effect on most fiber quality parameters, especially in environmentally challenging conditions.

Background Producing rainfed cotton (Gossypium hirsutum L.) with high fiber quality has been challenging in the Texas High Plains because of extended periods of insufficient rainfall during sensitive boll developmental stages. Genetic variation created by Ethyl MethaneSulfonate (EMS) mutagen has successfully improved fiber quality of cotton. However, little is known about the effect of water deficit environments on fiber quality. Three EMS treated populations were advanced from the first to the fourth generation (M1 to M4) as bulk harvested populations. In 2014, single-plant divergent selection was applied based on perceived morphological and agronomic differences seen during and at the end of the season. Results Analyses from these selections in 2014–2016 showed significant (P

Non-optimal application of nitrogen (N) fertilizer in cotton (Gossypium hirsutum L.) production systems often results from a producer’s uncertainty in predicting the N rate that ensures maximum economic return. Residual soil nitrate-N (NO3-N) is also often unaccounted for in fertilizer management decisions. In this study, the lint yield and profitability of two cotton cultivars (FiberMax FM 958 and Deltapine DP 1646 B2XF) were compared across five N fertilizer treatments [0 kg ha−1 (control), 45 kg ha−1 (N-45), 90 kg ha−1 (N-90), 135 kg ha−1 (N-135), 180 kg ha−1 (N-180)] from 2018 to 2020. For both cultivars, additional N fertilizer on top of the control treatment did not increase the lint yield of cotton. For each year, both control and N-45 treatments resulted in the greatest revenue above variable costs (RAVC) values for all cultivars. The improved N partitioning efficiency in newer cultivars and the high levels of residual soil NO3-N allowed sustained plant growth and yield even with reduced N application. Overall, the results show the advantage of reducing N inputs in residual N-rich soils to maintain yield and increase profits. These findings are important in promoting more sustainable agricultural systems through reduced chemical inputs and maintained soil health.

With the intensification and frequency of heat waves and periods of water deficit stress, along with rising atmospheric carbon dioxide [CO2], understanding the seasonal leaf-gas-exchange responses to combined abiotic factors will be important in predicting crop performance in semi-arid production systems. In peanut (Arachis hypogaea L.), the availability of developmental stage physiological data on the response to repeated water deficit stress periods in an elevated [CO2] (EC) environment is limited and necessary to improve crop model predictions. Here, we investigated the effects of season-long EC (650 µmol CO2 m−2 s−1) on the physiology and productivity of peanut in a semi-arid environment. This study was conducted over two-growing seasons using field-based growth chambers to maintain EC conditions, and impose water-stress at three critical developmental stages. Our results showed that relative to ambient [CO2] (AC), long-term EC during water-stress episodes, increased leaf-level light-saturated CO2 assimilation (Asat), transpiration efficiency (TE), vegetative biomass, and pod yield by 58%, 73%, 58%, and 39%, respectively. Although leaf nitrogen content was reduced by 16%, there was 41% increase in maximum Rubisco carboxylation efficiency in EC, indicating that there was minimal photosynthetic down-regulation. Furthermore, long-term EC modified the short-term physiological response (Asat) to rapid changes in [CO2] during the water-stress episodes, generating a much greater change in EC (54%) compared to AC (10%). Additionally, long-term EC generated a 23% greater Asat compared to the short-term EC during the water-stress episodes. These findings indicate high levels of physiological adjustment in EC, which may increase drought resilience. We concluded that EC may reduce the negative impacts of repeated water-stress events at critical developmental stages on rain-fed peanut in semi-arid regions. These results can inform current models to improve the projections of peanut response to future climates.

Recent technological advances in cotton (Gossypium hirsutum L.) phenotyping have offered tools to improve the efficiency of data collection and analysis. High-throughput phenotyping (HTP) is a non-destructive and rapid approach of monitoring and measuring multiple phenotypic traits related to the growth, yield, and adaptation to biotic or abiotic stress. Researchers have conducted extensive experiments on HTP and developed techniques including spectral, fluorescence, thermal, and three-dimensional imaging to measure the morphological, physiological, and pathological resistance traits of cotton. In addition, ground-based and aerial-based platforms were also developed to aid in the implementation of these HTP systems. This review paper highlights the techniques and recent developments for HTP in cotton, reviews the potential applications according to morphological and physiological traits of cotton, and compares the advantages and limitations of these HTP systems when used in cotton cropping systems. Overall, the use of HTP has generated many opportunities to accurately and efficiently measure and analyze diverse traits of cotton. However, because of its relative novelty, HTP has some limitations that constrains the ability to take full advantage of what it can offer. These challenges need to be addressed to increase the accuracy and utility of HTP, which can be done by integrating analytical techniques for big data and continuous advances in imaging.

Conservation management practices such as no-tillage and cover cropping can reduce soil erosion, enhance soil biological activity, increase water capture and storage, and sequester C. Cover crops, however, utilize stored soil water during the winter months, and the water depletion is thought to have negative impacts on the subsequent cotton (Gossypium hirsutum L.) crop in semi-arid ecoregions where water resources are limited. The objective of this research was to quantify the long-term impacts of conservation tillage and cover crop use on volumetric water content of soil in an irrigated cotton production system. Soil water was measured in a long-term (established 1998) conservation system in Lamesa, TX and water dynamics during the 2015–2017 growing seasons are presented here. Volumetric water content was reduced by cover crops prior to their termination but was replenished by spring precipitation and deficit irrigation prior to planting cotton. A stepwise regression analysis was used to determine changes in soil water at depth. In each of the study years, soil water increased more with no-tillage following cover crop termination and decreased less during cotton growth than the conventionally tilled system. Cotton water use efficiency was not significantly different between treatments in any year. Results from this study challenge the concept that winter cover crops result in reduced in-season soil water in irrigated systems, a supposition that has limited adoption of conservation tillage and cover crop use on the Texas High Plains.

In the semi-arid Texas High Plains, declining irrigation water supply hinders the profitable corn (Zea mays L.) silage production, the principle feed ingredient of the beef and dairy industries. Drought-tolerant and deep-rooting crops like forage sorghum (Sorghum bicolor L.) and pearl millet (Pennisetum glaucum L.) could be an alternative to corn silage under limiting irrigation. A field study was conducted during 2018 and 2019 at New Deal, TX to assess soil water depletion patterns, water use efficiency (WUE), and silage yield of forage sorghum, pearl millet, and corn under limited irrigation. The experiment was conducted in split-plot design with three irrigation levels [I0 (55 and 29 mm), I1 (172 and 147 mm), and I2 (323 and 260 mm) in 2018 and 2019, respectively] as main-plots and five cultivars [P1498AM (corn), AF7401 and Silo700D (BMR sorghum), and Epic and Exceed (BMR pearl millet)] as sub-plots with three replications. The soil water depletion amount was greater in I0 (105 and 57 mm) followed by I1 (60 and 37 mm) and I2 (44 and 13 mm) in 2018 and 2019, respectively. Fresh biomass yield was the greatest in I2 followed by I1 and I0; however, the highest WUE was achieved in I0 and I2 in 2018 and 2019, respectively. Water depletion depth was greater for sorghum and pearl millet plots (0–1 m) than corn plots (0–0.6 m) which resulted in greater water depletion amount in sorghum (75 and 31 mm) and pearl millet (68 and 48 mm) plots than corn (67 and 28 mm) during 2018 and 2019, respectively. Average yield and WUE were the highest in sorghum cultivars, followed by pearl millet and corn. Results confirmed that the higher silage yield and WUE can be achieved by sorghum compared to pearl millet and corn under limited irrigation conditions.

Cotton (Gossypium spp.) production around the world often occurs in water limiting environments. Although Upland (G. hirsutum) and Pima (G. barbadense) cottons have been evaluated under conditions of water stress before; these two species are rarely compared to each other. This may be due to differences in irrigation management and environmental constraints (i.e. season length). In 2014 and 2015, two Upland cultivars and two Pima germplasm lines were evaluated at Lubbock, TX, USA. Plant architecture, boll retention, lint yield and fiber quality were assessed under three deficit subsurface drip irrigation levels. Crop water use was evaluated using soil water balance in conjunction with neutron probe soil water content measurements. In 2014 during flowering at the high irrigation rate, Upland cultivars extracted significantly (p

Cotton producers on the southern High Plains of Texas face reduced seasonal irrigation capacities as groundwater resources from the Ogallala Aquifer decline. Technological advancements have allowed producers to achieve maximal water use efficiencies (>95 %); however, new management strategies are necessary to sustain producer profitability. By determining the optimal timing of irrigation, producers may be able to conserve irrigation water and reduce their pumping expenses. In a field experiment conduced from 2010 to 2013, cotton (Gossypium hirsutum L.) lint yield and profitability were compared across 27 irrigation treatments using a LEPA irrigation system on Pullman Clay/Olton soils. Irrigation was applied during three growing periods determined by growing degree days (GDD15.6), where P1=emergence to 525 GDD15.6, P2 = 525–750 GDD15.6, and P3 > 750 GDD15.6. Treatments for the experiment included three irrigation capacities of 0, 3.2, and 6.4 mm d−1 in a randomized block design with three replications. Profitability was assessed by calculating gross margin from economic budgets that included the management operations from each year. On average, treatments with an irrigation capacity of 0 mm d−1 in P1 made 6 % less yield, but saved 30 % more water and generated the same profitability as the IC treatments of 3.2 mm d−1. Irrigation during P3 at the 6.4 mm d−1 irrigation capacity (IC) was the most critical for yield potential, generating 114 % more yield than the 0 mm d−1 IC and 27 % more than the 3.2 mm d−1 IC treatments, resulting in a 468 % and 110 % increase in profit, respectively.

The Texas High Plains often has extended periods between rainfall events, which can lead to a reduction in the yield and fiber quality of cotton (Gossypium hirsutum L.). It is known that cultivated cotton suffers from low levels of genetic diversity due to the over-use in breeding of similar gene pools, which may hinder breeding for drought tolerance. In this study, for the first time the novel variability or genetic diversity of morphological and agronomic traits possibly created by the chemical mutagen ethyl methanesulfonate (EMS) was evaluated to improve drought tolerance in cotton by traits’ response to different irrigation regimes. EMS is a chemical mutagen that has been shown to cause point mutations in the DNA of many model plants and crop species. Three EMS treated lines were advanced from the M1 to M4 generation as bulk-harvested populations. A diverse selection scheme was applied to capture most of the genetic trait-variability or diversity and superior lines in these populations. In 2014–2016 the diversity of these populations was evaluated based on four agronomic and thirteen morphological traits to determine differences in response to multiple irrigation rates. Analyses of these traits showed statistically significant (p ≤ 0.05) differences between and within populations when compared to the original non-treated EMS source, with most of the variability being observed in the high irrigation rate. However, none of the EMS treated populations had significantly (p ≤ 0.05) better lint yield than the commercial cultivar (control) in 2016. EMS yield performance was possibly constrained by the applied diverse selection scheme of this study. Traits such as total number of bolls, bolls retained at node 7 and below, and those retained between nodes 8 and 12, and bolls retained at node of first fruiting branch may be predictors to improve cotton production (yield) in water limiting environments.

Evidence that supports a relation between AOX expression and improvement in plant height, internode length, and total leaf area under cool temperature is shown. Cell expansion and elongation appear to be enhanced when AOX expression was increased. Cotton growth is sensitive to cool temperature during germination and early seedling development. Delayed emergence, seedling damage, and increased risk to disease are common. Late seasonal cool weather is a major factor limiting the consistent production of high-quality cotton lint in West Texas. Alternative oxidase functions in the inner membrane of the mitochondria via an alternative respiration pathway and serves as a multifunctional system for amelioration of abiotic and biotic stresses. Cotton seedling emergence and growth exposed to cool temperatures was examined in plants with enhanced AOX expression. Thirteen T1 seed lines showed 3 to 1 segregation for the T-DNA containing the tobacco AOX1 gene. Two over-expressing, single-copy, homozygous AOX lines (94-20T and 66-6T) and Null line (94-3N) were selected for examination. The transcript levels were ≈ 2 to 6 fold higher in the AOX lines compared to those of the Null line and wild-type in stem, leaf, root and boll tissues. The research examined the hypothesis that transgenic cotton with enhanced AOX expression will have enhanced growth traits under suboptimal cool temperatures. Improved plant height, internode length, plant height and internode length from second node, and total leaf area under cool temperatures were observed in AOX over-expression lines. This may be attributed to improved cell expansion and elongation characteristics in the AOX line.

Within the Ogallala Aquifer Region of Texas, the irrigation capacity (IC) for a given field often changes within a growing season due to seasonal depletion of the aquifer, in-season changes in crop irrigation needs in dry years, or consequences of irrigation volume limits imposed by irrigation district rules. Irrigation planning is further complicated by erratic seasonal rainfall. A field experiment was conducted from 2010 to 2013 to determine cotton ( L.) irrigation productivity using a range of ICs common to the Texas South Plains during three irrigation periods. The treatments included in-season ICs (maximums of 0, 3.2, and 6.4 mm d-1) in combination with irrigation periods determined by accumulated growing degree days (GDD15.6) and were designated as period 1 (P1= emergence to 525 GDD15.6), period 2 (P2= 525 to 750 GDD15.6), and period 3 (P3>750 GDD15.6). Combinations of these factor levels resulted in 27 irrigation treatments with applications made by the low energy precision application (LEPA) method. Annual rainfall totals ranged from 137 to 557 mm over the four years. In all years, results indicated that attempting to store water in the soil profile, or irrigating in excess of the cotton evapotranspiration rate, early in the growing season reduced seasonal irrigation water use efficiency (SIWUE), and sometimes yield, compared to treatments with limited or no early irrigations. Treatments with 0 and 3.2 mm d-1 ICs during P1 used up to 20% less seasonal irrigation with minor yield loss (

Published in Agron. J. 107:1355–1364 (2015) doi:10.2134/agronj14.0502 Copyright © 2015 by the American Society of Agronomy, 5585 Guilford Road, Madison, WI 53711. All rights reserved. No part of this periodical may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or any information storage and retrieval system, without permission in writing from the publisher. ABSTRACT In the semiarid Texas Rolling Plains, the growth and yield of cotton (Gossypium hirsutum L.) is driven by the amount of water available to the crop through irrigation and precipitation. A field study was conducted in 2012 and 2013 at Chillicothe, TX, to investigate the growth, yield, water use efficiency (WUE), and spectral reflectance responses of cotton. A split-split plot design with three replications was used with irrigation as the main plot (three irrigation levels and dryland), tillage (no tillage and conventional tillage) as the subplot, and cultivars (PHY499, DP1044, PHY375, and FM9170) as the sub-subplot treatments. Plant height, lint yield, WUE, and fiber quality were significantly affected by irrigation and irrigation × cultivar interaction. Increasing irrigation level resulted in a linear increase in lint yield and WUE. The irrigation × cultivar interaction showed that the 90% evapotranspiration (ET) replacement treatment with PHY375 produced the greatest lint yield and WUE. Tillage did not significantly affect lint yield, WUE, or fiber quality. Increasing irrigation resulted in a linear increase in fiber length and strength, and a linear decrease in fiber micronaire. Two vegetation indices, normalized difference vegetation index (NDVI) and normalized difference water index (NDWI) were calculated using spectral reflectance measurements in this study. The NDWI increased steadily for all irrigation treatments during the measurement period. However, NDVI exhibited little change during the peak growth period between 79 and 89 d after planting. We suggest further investigation on using NDWI for irrigation management for cotton in the Texas Rolling Plains.

Petiole-NO3, leaf N and chlorophyll (SPAD) meter readings are good in-season indicators of the N status of the uppermost part of cotton (Gossypium hirsutum L.) plants. Petiole-NO3, particularly is widely used in the USA as an in-season plant N test that guides N fertilizer recommendations in cotton. However, these N status indicators do not take account of plant biomass, canopy width or percent cover. The objectives of this study were to assess the effect of N fertilizer rates on the commonly used indicators of plant N status; leaf N, petiole sap NO3 and chlorophyll meter (SPAD) readings and the plant growth measurements; plant height, canopy width, and percent ground cover, and determine to inter-correlations among the them. Irrigated field studies were conducted at Lubbock, TX USA in 2010 and 2011, New Deal, TX in 2010, and at Halfway, TX in 2011. Zero-N and a full N fertilizer rate of 134, 101, and 112 kg N ha−1 were used at Lubbock, New Deal, and Halfway, respectively. The 2010 cotton growing season in West Texas was much wetter than average, and the 2011 season was much drier than normal. As a result, plant height, canopy width, and ground cover were greater in the 2010 sites than in 2011. The effects of N fertilizer were greatest for the two cultivars in subsurface drip irrigation (SDI) at New Deal in 2010 for all three N status indicators, and for the three plant growth measures compared to the other site-years. Correlation analysis indicated that among the three plant N indicators, leaf N was the most sensitive to plant parameters. These effects were positive in 2010 and negative in the 2011 dry year. Petiole NO3 was the plant N indicator that was the most insensitive to plant growth, but the marked seasonal decline pattern reduces its usefulness for late-season N management.

The perennial growth habit of castor plants ( Ricinus communis L.) limits mechanical harvest because the plant grows very tall when the environmental conditions are favorable and produces many immature fruits, fresh stems, and green leaves at harvest time. There is a demand for chemicals that prevent excessive growth and defoliate the plant to prepare the crop to be harvested. This study had the objective of evaluating two growth retardants and three harvest aids (desiccants and defoliants) applied on castor crop at different times and doses. The experiments were conducted in Lubbock, TX, USA from 2007 to 2010. The growth retardants were Pix ® (mepiquat chloride) and Stance ® (mepiquat chloride + cyclanilide) applied one time at five development stages. The harvest aids were ET ® (pyraflufen), Ginstar ® (thidiazuron + diuron) + Finish ® (etephon + cyclanilide), and paraquat. The growth retardant Pix ® promoted rather than inhibited the vertical growth of castor plants, but in general, this product did not influence the seed yield. Stance ® did not influence vertical growth, but increased doses were associated with higher castor seed yields. The effect of Stance ® on seed yield was more intensive when applied from the 8th node stage through the first expanded leaf after the primary inflorescence. Early termination caused seed yield reduction compared with frost-killed plants, but the loss was progressively diminished as the termination occurred later in the season. There were differences in the effect of harvest aids. The reduction of mean seed yield caused by paraquat was not significant, but ET ® and Ginstar ® + Finish ® reduced the mean seed yield compared with untreated plants.