Soil Moisture Stress Conditions Research Articles

Phenotypic characterization of sesame (Sesamum indicum L.) revealed promising genotypes for moisture stress conditions

Abstract Soil moisture deficit is the major constraint for sesame crop production during its main rainfed and summer cultivation seasons. In summer cultivation, the crop frequently gets exposed to soil moisture deficit at various crop growth stages. Therefore, it is essential to identify the traits along with promising genotypes adapted to soil moisture deficit. A set of 35 sesame genotypes with checks was used to quantify the variation in morpho-physiological, yield, and quality traits under irrigated (WW) and deficit soil moisture stress (WS) conditions in the summer seasons of 2021 and 2022. The analysis of variance revealed the presence of high variability among the genotypes for various measured traits. The mean performance indicated that WS negatively affects the growth, development, yield and quality traits. Moreover, the correlation, path analysis and D2 analysis studies suggested that the traits, viz. leaf area (LA), total dry matter (TDM), canopy temperature (CT), number of branches per plant (NBP) and number of seeds per capsule (NSC) were significantly associated with seed yield under both the conditions. Quality traits like palmitic acid and oleic acid correlated positively with seed yield, particularly under WS. Furthermore, the genotypes with lower canopy temperatures were found to be better seed yielders under WS. In addition, mean performance and cluster analysis suggested that the genotypes: IC- 205776, JSCDT-112, JCSDT-26, IC-205610, and IC-204300, secured higher seed yield along with superior agronomical traits and net photosynthetic rate. These selected genotypes were most promising and could be used in future sesame crop improvement programmes.

Source and sink traits and their relationship under deficit soil moisture stress conditions in an indeterminate crop: sesame (Sesamum indicum L.)

ABSTRACT Sesame is an indeterminate oilseed crop where yield is determined by source and its capacity for synthesis and mobilization of photosynthates. Knowledge of the existing relation between source and sink and its validation under deficit soil moisture conditions is limited in sesame. Therefore, experiments were conducted using 25 sesame genotypes with differing plant architecture in terms of branching pattern (mono to multiple) and leaf area (minimum to maximum) under both irrigated (IR) and deficit soil moisture stress (DS) conditions for two consecutive years 2021 and 2022. The variations existing among the source and sink traits were measured, and the ANOVA of the measured traits revealed a significant differences among the genotypes for source traits, viz. leaf area, stem and leaf dry weight, net photosynthesis, total dry matter and their relationship with sink, i.e. seed yield under IR and DS conditions, and it was further confirmed using regression analysis. The results showed, certain source traits viz., stem dry weight and total dry matter at seed filling stage were positively associated with seed yield at both IR and DS conditions. Additionally, cluster analysis showed that the genotypes IC 54039-B-1 and SI 1802 had a proportional leaf area with good seed yield and displayed a better source and sink relationship, highlighting the fact that photosynthates were efficiently translocated to the sink. The genotypes IC 54039-B-1 and SI 1802 outperformed IR under DS with minimal yield differences and optimal leaf weight, total dry matter, and plant stem weight. These genotypes with better source and sink relationships can be used in sesame crop improvement programmes.

Impact of temperature and soil moisture on paddy weed and productivity: A case of Lalitpur District, Nepal

Rice (Oryza sativa L.) is a major food crop for around 60% of the global population. The production of rice has been challenged by various biotic and abiotic factors. Temperature and soil moisture are the major abiotic and weeds are the major biotic factors for yield loss. The present experiment was conducted to investigate the impact of temperature and soil moisture on rice weed and rice productivity. The experiment was carried out under different temperatures (ambient, ambient +2°C, and ambient +3°C) and soil moisture (ambient, 25-30%, and 10-15%) conditions for the entire crop growth period from June to October 2014. Rice weeds were recorded after 28, 47 and 93 days of rice transplantation for varied soil moisture. Similarly, at varied temperature weeds were recorded after 19, 44 and 66 days of rice transplantation. The results showed that weed density increases under elevated temperature at 2°C and 3°C than under an ambient condition (existing in the surrounding area). An experiment on soil moisture stress indicates a reduction in rice productivity as the density of weed increases with the deficiency of soil moisture. Further studies on temperature and soil moisture resisting rice variety are essential. This study suggests that research on the control of weed species, targeting those weeds benefited at elevated temperature and soil moisture stress conditions, is necessary.

Amplified signals of soil moisture and evaporative stresses across Poland in the twenty-first century

In Poland, recent summer droughts have had devastating environmental, social, and economic consequences, but the trend of growing season dryness remains unclear. This study focuses on the soil moisture and evaporative stress conditions, analyzed in a multiyear period between 1981 and 2019. Country scale trends in growing season drought severities are assessed using indices derived from the model-based estimates of soil moisture and evapotranspiration. These are compared with indices derived from meteorological variables. Soil droughts are assessed by the Standardized Soil Index (SSI), while the ecological droughts are related to evapotranspiration by the Standardized Evaporative Stress Ratio (SESR). Moreover, the Standardized Precipitation Index (SPI), Standardized Precipitation Evapotranspiration Index (SPEI), and self-calibrating Palmer Drought Severity Index (sc-PDSI) are used for comparison. A Drought-Prone Area (DPA) is delineated based on a criterion defined as simultaneous occurrence of statistically significant drying trends in surface and root zone soil moisture and evaporative stress. It was found that soil and ecological drought severities have remarkably increased in the growing season. This confirms the hypothesis that intensified soil drying is accompanied by intensified water stress imprinted in evapotranspiration. The most severe drought sequence has occurred in recent years, amplified by exceptionally high air temperature, low precipitation, and high deficit in the climatic water balance. The highest correlation is observed between annual growing season drought severities derived from the SSI and SESR; only SPEI approximates an increasing trend, while the SPI and sc-PDSI do not follow such a trajectory. The study shows an almost contiguous spatial pattern of DPA, which takes 42% of the country. One important implication of this study is that soil moisture and evapotranspiration should be considered in assessing drought severity in addition to traditionally used meteorological variables.

Genome-wide Association Mapping for the Identification of SNPs Controlling Lateral Root Plasticity in Selected Rice Germplasms of the Philippines

Lateral root plasticity is a key adaptive mechanism for drought and fluctuating moisture-induced stresses in rice. Thus, understanding the genetic control of lateral root plasticity is important to enhance the climate-resilience and productivity of rice in abiotic stressed-prone environments. Genome-wide association analysis was conducted on a selected panel of traditional rice varieties (TRVs) to find single nucleotide polymorphisms (SNPs) associated with root plasticity traits under different gradients of soil moisture stress. A total of 17 SNPs, which were significantly correlated to root plasticity traits under soil moisture stress conditions, were located in six chromosomes (2, 5, 7, 9, 10, and 12). Additionally, the accessions that showed high plasticity in total lateral root length (TLRL) under severe drought were identified from among the TRVs and assumed to possess the lone SNP associated with the trait found in Chromosome 2. Specifically, the Baksalan Kawalwal accession showed an increase in L-type lateral root length under fluctuating soil moistures (SMF) (+10.31 m) and progressive drought (PDR) (+0.90 m), relative to their continuously waterlogged (CWL) counterparts under rootbox pinboard system. This may suggest the performance of the SNP in controlling the promotion of lateral roots. Furthermore, a possible candidate gene found near the SNP in Chromosome 2 is a member of PYR/PYL/RCAR-like protein family of abscisic acid (ABA) receptors, likely suggesting that plasticity in lateral root development in rice under severe drought could be regulated by ABA. Taken together, these novel root plasticity SNPs and the respective candidate genes on Chromosome 2 have potential use in developing climate-smart rice varieties.

Sustainable effect of a symbiotic nitrogen-fixing bacterium Sinorhizobium meliloti on nodulation and photosynthetic traits of four leguminous plants under low moisture stress environment.

Sustainable effect of a nitrogen-fixing bacterium Sinorhizobium meliloti on nodulation and photosynthetic traits (phenomenological fluxes) in four leguminous plants species under low moisture stress (20-25% soil moisture content) environment was studied. Sinorhizobium meliloti was isolated from fenugreek (Trigonella foenum-graecum) root nodules, and later, it was cultured and purified. Nodulation and photosynthetic ability in the presence of S. meliloti were tested in four leguminous plant species, that is, kidney bean (cv. lobia-2000), black bean (cv. NM-97), mung bean (cv. NM-2006) and chickpea (cv. Pb-2008). Plants of each species were grown in sterilized soil that was previously treated with 25ml suspension containing S. meliloti at 41×106 CFUml-1 kg-1 pot. One-month-old plants were subjected to low soil moisture stress conditions for 15days, and soil moisture contents were maintained to 20-25% throughout the experimental period. The ability to fix nitrogen, nodule formation, and their subsequent effect on phenomenological fluxes in low moisture treated legumes were studied.

Propagation and Possible Allelopathic Effects of Vernoniazeylanica on Selected Bioassay Species

Vernonia zeylanica (L.) belongs to the family Asteraceae, is one of the major endemic weed species present in coconut (Cocos nucifera L.) plantations of the tropics, which propagates very easily. There is a possibility that this plant could also possess allelopathic effects, but this has not been scientifically tested. Thus, a study was carried out to determine the seed germination of V. zeylanica under soil moisture stress conditions, shoot propagation methods and possible allopathic effects of this species, on selected species in bioassay tests. Germination of V. zeylanica seeds was not observed at higher osmotic potential (-0.9 MPa). The highest sprouting percentage of this species were obtained with soft wood cuttings. The aqueous leaf extract was highly phytotoxic, and it significantly reduced germination and seedling growth of all bioassay species tested. Full strength (33.3 g L-1) aqueous extracts of leaves significantly reduced the germination percentage, root and hypocotyl growth rates of all species tested. The inhibitory effects were often dependent on concentration. However, the degree of inhibition varied among the test plant species. The seedling emergences of all four tested plants were severally inhibited when planted in V. zeylanica contaminated soil. The results indicated that incorporated aqueous leaf extract of V. zeylanica and its rhizosphere contaminated soil can suppress seed germination, seedling growth and seedling emergence of certain plant species indicating a possible allelopathic effect.

Influence of soil temperature and moisture on micronutrient supply, plant uptake, and biomass yield of wheat, pea, and canola

Crop yield response to micronutrient fertilization is difficult to predict, particularly under unfavorable environmental conditions as these may alter both crop nutrient demand and the soil micronutrient supply to plant roots. The research objective was to evaluate the effect of various soil temperature and moisture conditions on crop growth response to added micronutrient copper (Cu), zinc (Zn), and boron (B) along with soil micronutrient supply and distribution among fractions. Brown and Dark Brown farm soils collected from southern Saskatchewan were used to grown wheat, pea and canola within controlled environment chambers. The biomass yields of all crops decreased under cold soil temperature and moisture stress (drought and saturated) conditions. Greater plant uptake of Cu, Zn, and B was associated with optimum (i.e., field capacity) soil moisture and warm temperature (23°C) growing conditions, compared to drought (i.e., 50% field capacity), saturated, and cold (5°C) temperature conditions. Environmental stress had the greatest impact on pea growth, reducing crop yield and micronutrient utilization efficiency more than 95%. Soil supplies of Cu and Zn were most negatively impacted by drought stress due to reduced mobility of these diffusion limited nutrients. The extractable micronutrients levels and chemical speciation fractions of Cu, Zn, and B indicating that bioavailability and micronutrient transformation were not affected during our short-term (i.e., six-weeks) study. However, it is suggested that assessments of micronutrient forms also be conducted on soil samples under actual moisture and temperature conditions as they exist in the experiment, as well as on dried, processed samples.

Effect of Cow Urine-Based Bioformulations on Growth and Physiological Responses in Mungbean Under Soil Moisture Stress Conditions

Experiments were conducted to evaluate the influence of cow urine-based bioformulations on the morphological, physiological growth response and expression of stress responsive genes under drought stress in mungbean [Vigna radiata (L.) Wilczek] plants. An initial in vitro evaluation and three separate pot experiments were carried out by treating mungbean with varying concentrations of bioformulations under different soil moisture conditions (well watered and water stressed). The application of bioformulations (BR and SH) led to an increase in number of nodules (22.41 in R3 stage under stress; 12.17 in R5 stage under stress recovery) and total plant dry weight (1.12 g in R3 stage under stress; 1.22 g in R5 stage under stress recovery) at different growth stages and soil moisture conditions. Least decrease or no change in photochemical efficiency of PS-II (Fv/Fm) in the bioformulations-treated plants under stress-imposed conditions indicated that bioformulations used in this experiment have potential role in mitigating soil moisture stress in crops like mungbean. The enhanced expression of genes of membrane-integrated protein like aquaporins (Nodulin 26-like Intrinsic Proteins—NIP) in the treated plants under low soil moisture conditions further accentuated the efficacy of these bioformulations to alleviate the drought stress in crops.

A study on soil moisture model for agricultural water management under soil moisture stress conditions in Sikkim (India)

Soil moisture is a critical component of the earth system that impacts on the water, energy and bio-geochemical cycles. A soil moisture study was conducted for agricultural water management of selected crops in Sikkim (India). An effort was made to quantify extent of soil moisture stress and to develop a soil moisture model for estimating irrigation water requirement. In the study, it was observed that significant stress exists in Sikkim (ranging from 600 to 1620.21 kPa). It has been reported that soil moisture stress above 100 kPa constrains the water uptake capability of any plant and thus it needs to be replenished artificially through irrigation. For efficient irrigation water management, it is necessary to estimate the irrigation requirement. The irrigation requirement was estimated using the developed model for selected crops of Sikkim. The models were tested using various performance assessment parameters such as coefficient of determination (R2) (0.76, 0.66 and 0.63), root mean square error (RMSE) (3.00–6.5%) and mean relative error (MRE) (3–9.18%) for selected locations, viz., Mangan, Pangthang and Gyalshing. The estimated annual irrigation requirement for the selected crops varied from 31.7 to 185.06 mm at different locations, viz., Mangan, Pangthang and Gyalshing.

Canopy temperature depression (CTD) and canopy greenness associated with variation in seed yield of soybean genotypes grown in semi-arid environment

Method to measure canopy temperature depression (CTD) by employing thermal imaging system for crops like soybean, which is sensitive to low soil moisture has not been standardised/optimised. Hence, the present study was conducted to optimise the thermal imaging method and evaluated the CTD along with canopy greenness-based physiological traits in screening/selecting soybean genotypes suitable for semi-arid environment. The CTD and canopy greenness were measured six to eight times during different growth phases/stages using infrared (IR) and visible cameras mounted on a semi-automatic trolley that allowed rapid acquisition of high quality thermal and visible images, respectively. The CTD measured at the reproductive stage explained a major proportion of the variation in grain yield under both well-watered and water-stressed conditions. This could be attributed to close association between plant's capacity to keep its canopy cooler (low canopy temperature) and canopy greenness (higher chlorophyll content) as indicated by efficient photosynthesis which leads to grain yield. These results indicated that in addition to assess stay green features, CTD along with canopy greenness can also be used as a key trait of leaves in the selection of soybean genotypes for higher adaptability to low soil moisture stress conditions, a common feature exists under semi-arid regions.

Yield and water use efficiency of potato varieties under different soil-moisture stress conditions in the Fergana Valley of Central Asia

ABSTRACTDeficit irrigation could be considered as one potential option to improve water productivity and obtain some level of assured income under water scarcity and drought conditions in Central Asia. This article investigates water productivity and economic returns to two varieties of potato crop under four different soil-moisture regimes in Uzbekistan. Results suggest that deficit irrigation may not be considered as an option to improve water productivity of potato crop, particularly when the deficit is high. However, deficit irrigation options could be still considered as a viable option to maintain food security and some assured farm income even under extreme drought conditions.

Seed Priming with Polyethylene Glycol Induces Physiological Changes in Sorghum (Sorghum bicolor L. Moench) Seedlings under Suboptimal Soil Moisture Environments.

Osmopriming with PEG has potential to improve seed germination, seedling emergence, and establishment, especially under stress conditions. This research investigated germination performance, seedling establishment, and effects of osmopriming with PEG on physiology in sorghum seedlings and their association with post-priming stress tolerance under various soil moisture stress conditions. Results showed that seed priming increased the environmental range suitable for sorghum germination and has potential to provide more uniform and synchronous emergence. Physiologically, seed priming strengthened the antioxidant activities of APX, CAT, POD, and SOD, as well as compatible solutes including free amino acid, reducing sugar, proline, soluble sugar, and soluble protein contents. As a result, seed priming reduced lipid peroxidation and stabilized the cell membrane, resulting in increased stress tolerance under drought or excessive soil moisture environments. Overall, results suggested that seed priming with PEG was effective in improving seed germination and seedling establishment of sorghum under adverse soil moisture conditions. Osmopriming effectively strengthened the antioxidant system and increased osmotic adjustment, likely resulting in increased stress tolerance.

Clonal variation of tea [Camellia sinensis (L.) O. Kuntze] in countering water deficiency

Various clones of tea [Camellia sinensis (L.) O. Kuntze] such as TTL-1, TTL-2, TTL-4, TTL-5, TTL-6, UPASI-2 and UPASI-3 planted in the field were subjected to soil moisture stress conditions by withholding irrigation. A control set of the same clones were maintained by watering regularly. The soil water content of the irrigated and non irrigated plants was monitored through the soil moisture status. The extent of effect of drought on tea plants were monitored through various physiological parameters such as shoot weight, leaf water potential, chlorophyll and carotenoid content, chlorophyll fluorescence (Fv/Fm), net photosynthetic rate, transpiration rate, stomatal conductance and biochemical parameters such as extent of proline accumulation and free radical generation. These parameters were studied on the 30d of non irrigation and on the 5d during recovery from drought. The plants recovered when re-irrigated after 30d of non-irrigation, which suggests that permanent wilting did not occur due to non-irrigation up to 30d. On the 30d of non-irrigation the clones TTL-1, TTL-6 and UPASI-2 showed lesser reduction of shoot weight, leaf water potential, chlorophyll fluorescence, photosynthetic rate, transpiration rate and stomatal conductance and increased proline and lesser lipid peroxidation as compared to the other clones. From these results it can be concluded that the clones TTL-1, TTL-6 and UPASI-2 are comparatively more drought tolerant than the clones TTL-2, TTL-4, TTL-5 and UPASI-3.

Stability of soil plant analytical development (SPAD) chlorophyll meter reading (SCMR) and specific leaf area (SLA) and their association across varying soil moisture stress conditions in groundnut (Arachis hypogaea L.)

The complex nature of physiological traits associated with drought tolerance and the difficulties associated with their measurements in segregating populations and large number of genotypes inhibited their use in the past in developing water-use efficient genotypes in breeding programmes. With new knowledge of easily measurable surrogates of transpiration efficiency (TE), a trait associated with drought tolerance—specific leaf area (SLA) and soil plant analytical development (SPAD) chlorophyll meter reading (SCMR), it is now possible to integrate TE through the surrogates in breeding and selection schemes in groundnut (Arachis hypogaea L.). As a noninvasive surrogate of TE, SCMR is easy to operate, reliable, fairly stable and low cost. However, in a large-scale breeding program, it is difficult to complete SCMR observations within a specified time. The present study addressed the issue as to what extent the SCMR measurements can be spread over time by evaluating 18 diverse groundnut genotypes for two physiological traits, SCMR and SLA in two postrainy (Nov–Apr) seasons (2002/2003 and 2003/2004) in India. Observations were recorded at different times during and after the release of moisture deficit stress. There was general agreement in genotype and trait performance in both the seasons. Interaction between SCMR and time of observation was significant in only one season (2002/2003) but its variance relative to genotypes and time of observation was very small. ICGV 99029 and ICR 48, which recorded higher SCMR and lower SLA values in both the seasons, will make good parents for water-use efficiency trait in breeding programmes. Other good parents include ICGS 76, TCGS 647 and TCGP 6. SCMR recorded at three different times under differing soil moisture deficit in each season showed highly significant correlation with each other. Similarly, SLA at different times also correlated significantly with each other. SCMR and SLA were significantly negatively correlated with each other and the relationship was insensitive to time of observation. The results of the present study indicated that SCMR/SLA observations can be recorded at any time after 60 days of crop growth, preferably under moisture deficit conditions. This gives groundnut breeders a large flexibility to record these observations in a large number of segregating populations and breeding lines in the field. Thus, making it easy to incorporate these physiological traits associated with drought tolerance in breeding and selection scheme in groundnut.

Genotypic Variation in Root Systems of Chickpea (Cicer arietinum L.) across Environments

AbstractRoot systems of various chickpea genotypes were studied over time and in diverse environments, – varying in soil bulk density, phosphorus (P) levels and moisture regimes. In a pot study comparing a range of chickpea genotypes, ICC 4958 and ICCV 94916‐4 produced higher root length density (RLD) and root dry weight (RDW), which were better expressed under P stress conditions. In two field experiments in soils of intermediate and high soil bulk densities, ICC 4958 also had greater RLD and RDW, particularly under soil moisture stress conditions. The expression of greater rooting ability of ICC 4958 under a wide range of environmental conditions confirms its suitability as a parent for genetically enhancing drought resistance and P acquisition ability. The superiority of ICC 4958 over other genotypes was for root proliferation expressed through RLD. Thus, the variation in RLD can be the most relevant root trait that reflects chickpea's potential for soil moisture or P acquisition.

Tree Canopy Effects on Simulated Water Stress in Southern African Savannas

A coupled energy and water balance model is used to simulate the effects of large tree canopies on soil moisture and water stress across a series of sites spanning a regional moisture gradient in southern Africa. The model tracks evapotranspiration from five components of the land surface at each site—the tree canopy, the grass under and between tree canopies, and the bare soil under and between tree canopies. The soil moisture dynamics are simulated at daily time steps and driven by a stochastic model of storm arrivals and storm depth. Evapotranspiration is modeled using the Priestley-Taylor approach, with potential evapotranspiration scaled by soil moisture availability. The soil moisture under tree canopies is compared to the soil moisture between tree canopies, and differences in average annual soil moisture stress conditions are analyzed at each site. The spatial distribution of large trees has important consequences for small-scale soil moisture dynamics across the rainfall gradient. The results indicate that tree canopies serve to reduce soil moisture stress of under-canopy vegetation in the middle of the rainfall gradient. At the dry end of the rainfall gradient, the effect of tree canopies on soil moisture is dependent on the amount of rainfall received in a given growing season.

Gender-specific responses to winter defoliation of greenhouse-grown Atriplex canescens clones under contrasting soil moisture regimes

A greenhouse experiment with female, male and monecious clones (36 of each, 108 total) of tetraploid Atriplex canescens (Pursh) Nutt. (fourwing saltbush) was conducted to determine gender-specific responses to simulated herbivory under contrasting conditions of soil moisture. We imposed three levels of winter defoliation (control, 40%, and 70% stem removal) and two soil moisture treatments (control and water stress). Gender-related responses to defoliation were context-specific. Defoliated female clones produced significantly less shoot biomass than male or monecious clones when soil moisture conditions were not limiting. All genders produced similar amounts of shoot biomass under conditions of soil moisture stress. Root biomass responses exhibited the opposite trend. With adequate soil moisture all defoliated clones produced similar amounts of root biomass, but water-stressed defoliated females usually produced less root biomass than their male and monecious counterparts. Leaf gas-exchange measurements indicated that females were less efficient than males in the use of water. Monecious clones outperformed both females and males when conditions of stress were greatest. Defoliated female shrubs may be at a competitive disadvantage regardless of the environmental context, and could therefore be expected to be the shrub gender most negatively affected by herbivory.

Diversity for osmotic adjustment and root depth in TEF [ Eragrostis tef (Zucc) Trotter

Osmotic adjustment (OA) and deep roots were shown to be important drought resistance mechanism in many crop plants. In this study, geno types systematically selected from an Ethiopian endemic tef [Eragrostis tef (Zucc) Trotter] germplasm pool were evaluated for osmotic adjustment and root depth in greenhouse in several experiments. The association of these traits with other plant characters was also studied. Osmotic adjustment was investigated in two experiments. Experiment 1 was conducted using nine genotypes for two seasons (spring and fall 1996), and experiment 2 was undertaken in the spring of 1997 with 45 genotypes. In experiment 1, there were significant genotype effects on OA. Though there was also significant genotype by season interaction for OA, some of the extreme lines gave consistently high (Ada and DZ-01-99) and low (DZ-01-354 and Trotteriana) OA values across seasons. There was a significant variation among genotypes for OA in experiment 2. Osmotic adjustment was not associated with the altitude of the region of origin of the particular tef genotype. In both experiments, OA was significantly correlated across tef genotypes with delayed wilting and the maintenance of higher relative water content (RWC) under conditions of soil moisture stress. Three experiments were conducted to evaluate the phenotypic diversity for root depth. In all experiments tef genotypes differed significantly for root depth as measured at flowering time. The late maturing genotypes tended to have greater root depth as compared to early maturing genotypes. Root depth was not associated with the altitude of the region of origin of the tested genotypes. There was no association between root depth and OA across genotypes.

Control and Seedhead Suppression of Red Rice (Oryza sativa) in Soybeans (Glycine max)

Experiments were conducted in 1985 and 1986 at three locations in eastern Arkansas to evaluate red rice control in soybeans with postemergence grass herbicides and plant growth regulators applied singly or sequentially at early to late-tillering growth stages of red rice. Haloxyfop at 0.21 kg ai/ha and quizalofop at 0.14 kg ai/ha applied singly or sequentially and fluazifop at 0.21 kg ai/ha applied sequentially consistently controlled red rice and suppressed seedhead production in soybeans. Mid-season treatments were not beneficial when high soil moisture stress conditions existed. Mefluidide or sethoxydim applied singly or sequentially or amidochlor applied singly provided erratic control and seedhead suppression of red rice in soybeans.