Normal Planting Dates Research Articles

Effect of ultra‐early, early, and normal soybean planting dates and rye cover crop on soybean grain yield

AbstractWith changes to climate and crop insurance, earlier soybean [Glycine max (L.) Merr.] planting dates need to be investigated. Additionally, the use of a cover crop prior to soybean is promoted as a sustainable practice though little is known about cover crop and ultra‐early soybean planting (prior to April 15). The objective was to evaluate soybean planting date and cereal rye (Secale cereale L.) cover crop termination timing on cover crop biomass, soybean plant population, and yield. The study was conducted in Northeast and West Central Ohio in 2021 and 2022. Treatments included three soybean planting dates (early April, late April, and late May) and three cover crop treatments (termination 1–2 weeks prior to planting or “early,” termination at or after planting or “late,” and no cover crop). Cover crop biomass increased as termination was delayed. Soybean planted in early April resulted in a yield reduction of 1.8 Mg ha−1 when planted into a cover crop compared to the no cover crop control. However, when soybean was planted in late April, grain yield was not different among cover crop treatments. Yield reduction associated with early April planting with a cover crop was likely due to low soybean plant population, especially in Northeast Ohio, where plant population was <55,000 plants ha−1 with a cover crop and >120,000 plants ha−1 without a cover crop. To maximize yield, soybean should be planted by the end of April in Northeast Ohio. In West Central Ohio, soybean can be planted in early April without a cover crop.

Impact of Variety and At-Planting Insecticides on Thrips (Thysanoptera: Thripidae) Management in Peanut

Tobacco thrips are one of the most prevalent early season insect pests in peanut production systems. Experiments were conducted in 2018 and 2019 in Stoneville Mississippi to evaluate integrated pest management approaches to mitigate negative effects of thrips. Experimental treatments included a normal and late planting date, varieties Georgia-06G and QR-14, and in-furrow insecticide treatments consisting of a non-treated control, phorate, and imidacloprid. Measurements included early and final plant stands, immature and adults thrips counts, and pod yield. In-furrow insecticide had a strong effect on number of thrips per plant with treatment thrips ranking of: phorate < imidacloprid < non-treated control. However, in-furrow insecticide had no interaction with variety or plating date. Although phorate provided greater thrips control than imidacloprid, pod yield for the two treatments was similar, and both in-furrow treatments had greater yield than the non-treated control. The variety QR-14 had greater pod yield than Georgia-06G when planted late. Overall, these results confirm that in-furrow insecticide applications of either imidacloprid or phorate are adequate in protecting against yield loss from thrips within a midsouthern peanut production environment.

The impact of future climate on orange-fleshed sweet potato production in arid areas of Northern Ethiopia. A case study in Afar region

Sweet potato is in its introductory phase as a food-based approach to alleviate malnutrition in the Afar region, where, due to climate change, agricultural drought impedes crop production. This study assesses the impact of climate change on orange-fleshed sweet potato (OFSP) fresh storage root yield production over the Afar region using the Aqua Crop model. This model was fed with daily rainfall and minimum and maximum temperature datasets, for the baseline climate (1980–2009) as well as future (2010–2099) climate projections under two representative concentration pathways: RCP 4.5 and RCP 8.5. These datasets were statistically downscaled from twenty (20) general circulation models that are used in the Coupled Model Intercomparison Project Phase 5 (CMIP5). The impact of climate change on sweet potatoes was assessed by comparing the change in average sweet potato yields in the baseline climate condition against the average of simulated sweet potato yields in the Near-term (NT) (2010–2039), Mid-term (MT) (2040–2069), and End-term (ET) (2070–2099) under RCP 8.5 and RCP 4.5. Simulation shows increased future storage root yield production for NT (3.23%), MT (3.90%), and ET (7.25%) under RCP 4.5 and MT (5.88%) and NT (6.71%) from the observed yield data (32.0 t/ha) except for Near-term (−9.59%) under RCP 8.5. Similarly, projected climate shows increase in temperature Tmax (0.93–4.10 °C), Tmin (0.88–4.54 °C) and precipitation (28.9–37.8%) under both RCPs which will favor sweet potato yield production increase in near-term, mid-term reaching climax in end-term. Simulation with planting dates shows that normal planting date (July 01), gives better yields than early (April 22) or late planting (01 August). This finding may perhaps be used as preliminary data in adoption and upscaling of orange-fleshed sweet potato in Afar region.

Reducing potato water footprint by adjusting planting date in the agro-pastoral ecotone in North China

Reducing the water footprint per unit of crop production reduces the pressure on the limited freshwater resources. This study used data from a four-year field experiment conducted in the agro-pastoral ecotone (APE) of Northern China, to calibrate and validate the APSIM-Potato model, and determine the impacts of planting dates on the water footprint (WF) of potatoes under rain-fed and irrigated conditions. Results showed that the rain-fed potato yields were 14.6, 18.9, and 19.9 t ha−1, under the early, normal, and late planting dates, respectively, and the irrigated yields were 19.7, 31.8, and 30.9 t ha−1 under the three planting daets. The blue WF of the potatoe were -25.6–0 m3 t−1, -27.2–0 m3 t−1, and -26.4–0 m3 t−1 in early, normal, and late planting dates, respectively, under rainfed condition, and the value was highest in normal planting date. Green WF of the potato was 24.4 m3 t−1, 16.0 m3 t−1, and 13.5 m3 t−1 under early, normal, and late planting dates, respectively. The total WF was 20.3 m3 t−1 under the early planting dates, which was 50.3% and 87.9% higher than that under normal and late planting dates, respectively. Under the irrigated conditions, early planting exhibited the highest blue WF (33.2–77.9 m3 t−1), followed by normal (32.1–67.4 m3 t−1), and late planting dates (26.6–61.3 m3 t−1). The green WF was 104.9 m3 t−1 under the early planting dates, which was 48.8% and 45.9% higher than that under normal and late planting dates. Furthermore, the total WF of potatoes decreased with delayed planting, with the average values of 161.1, 117.8, and 114.2 m3 t−1 under early, normal, and late planting dates, respectively. These findings suggest the potential of reducing potato WF across the APE by adjusting the planting dates.

Spectral Reflectance Indices as a High Throughput Selection Tool in a Sesame Breeding Scheme

On-farm genotype screening is at the core of every breeding scheme, but it comes with a high cost and often high degree of uncertainty. Phenomics is a new approach by plant breeders, who use optical sensors for accurate germplasm phenotyping, selection and enhancement of the genetic gain. The objectives of this study were to: (1) develop a high-throughput phenotyping workflow to estimate the Normalized Difference Vegetation Index (NDVI) and the Normalized Difference Red Edge index (NDRE) at the plot-level through an active crop canopy sensor; (2) test the ability of spectral reflectance indices (SRIs) to distinguish between sesame genotypes throughout the crop growth period; and (3) identify specific stages in the sesame growth cycle that contribute to phenotyping accuracy and functionality and evaluate the efficiency of SRIs as a selection tool. A diversity panel of 24 sesame genotypes was grown at normal and late planting dates in 2020 and 2021. To determine the SRIs the Crop Circle ACS-430 active crop canopy sensor was used from the beginning of the sesame reproductive stage to the end of the ripening stage. NDVI and NDRE reached about the same high accuracy in genotype phenotyping, even under dense biomass conditions where “saturation” problems were expected. NDVI produced higher broad-sense heritability (max 0.928) and NDRE higher phenotypic and genotypic correlation with the yield (max 0.593 and 0.748, respectively). NDRE had the highest relative efficiency (61%) as an indirect selection index to yield direct selection. Both SRIs had optimal results when the monitoring took place at the end of the reproductive stage and the beginning of the ripening stage. Thus, an active canopy sensor as this study demonstrated can assist breeders to differentiate and classify sesame genotypes.

Diverging water-saving potential across China's potato planting regions

China ranks the first in total planting area and production of potato (Solanum tuberosum L.) over the world. However, high potato yield depends on a large amount of irrigation that raises a series of environment problems. Assessing the water-saving potential across China’s potato planting regions is of importance for maintaining sustainable development of potato production. In this study, we firstly evaluated the potential yields, rainfed yields, and their gaps of potato across different potato planting regions, and then presented optimal agronomic management options (planting date, cultivar maturity, and irrigation schedule) by considering both yield and water use efficiency of potato under the limitation of available water resources with validated APSIM-Potato model. Along the distribution of growth period solar radiation, potential yield of potato was highest in the North Single planting region (NS), followed by the Central Double planting region (CD), Southwest Mixed planting region (SWM), and South Winter planting region (SW). However, rainfed yield of potato was highest in CD followed by NS, SW, and SWM along the distribution of the reproductive growth period precipitation. Under the limitation of available water resources, most potato planting regions should select middle−late maturing cultivars while optimal planting dates varied among regions with earlier planting in north China and later planting in south China compared with normal planting date. Based on the optimization of planting date, cultivar maturity, and irrigation schedule, there is a large water-saving potential in China’s potato planting regions. Average irrigation amount could be decreased by 66% in SW, 49% in SWM, 40% in NS, and 29% in CD, respectively, relative to irrigation quota. Our study suggests that optimizing planting date, cultivar maturity, and irrigation management could realize win-win of yield and water use efficiency and provide a scientific support for water-saving irrigation of potato production in China.

Effects of Silicon and Zinc Sources on Quantitative and Qualitative Characteristics of Canola at Normal and Late Planting Dates

In order to study the effects of silicon (Si) and zinc (Zn) sources on yield components, seed yield, seed oil content and nutrient concentrations in canola grain at normal and late planting dates, a field experiment was conducted as a split plot-factorial in a randomized complete block design with three replications at Ghaemshahr Agricultural Research Station during the 2017-2018 and 2018-2019 growing seasons. Planting dates as the main plot at two levels (normal planting date, late planting date), silicon fertilizer sources at three levels (control, calcium silicate, nano-Si) and zinc fertilizer sources at three levels (control, zinc sulfate, nano-Zn) were considered as sub-plots. The results showed that all the agronomical and physiological traits studied improved in the normal planting date, while delay in planting date led to a significant reduction in the traits. Application of Si and Zn by both nanoparticles (NPs) and conventional forms significantly increased the yield components, seed yield, seed oil content and nutrient uptake in grain compared to the control plants. There was no significant difference between application of nano-Si and calcium silicate in terms of rapeseed yield and quality. The nano-Zn treated plants showed both higher seed yield and higher nutrient uptake, when compared to zinc sulfate treated plants. The combined application of Si with Zn, especially in the form of nanoparticles resulted in higher seed oil content than the application of Si or Zn alone. In general, the application of Si and Zn in the form of nanoparticles at normal planting date is a promising option to increasing seed yield and improving nutrient uptake in rapeseed.

Optimal planting dates for diverse crops in Inner Mongolia

Climate warming and water resource shortage are severely threatening crop production in Inner Mongolia. Selecting optimal planting date (OPD) is recognized to be an effective way in alleviating water stress by matching crop water requirement with natural precipitation. However, optimal planting dates and drought resistance of staple crops have been not investigated in this region. In this study, the validated APSIM model was used to identify the OPD and crop drought degree for six staple crops including canola, edible sunflower, maize, oats, oil sunflower, and potato through comparing the potential and rainfed yields under different planting dates. The study results showed that OPD varied among crops and regions. Maize had the earliest OPD followed by canola, oil sunflower, oats, potato, and edible sunflower. Optimizing planting date could boost crop yields by increasing precipitation use efficiency. Compared with normal planting date, mean yields and precipitation use efficiencies for staple crops under OPD could be increased by 1%–54% and 7%–119%, respectively in Inner Mongolia. Oats, potato, and canola had higher drought-resistance than other three crops and showed less yield reduction rates and yield variations from potential to rainfed conditions. January–March precipitation (or mean temperature) could be used to determine the OPDs of oats and potato (or edible and oil sunflower), while April precipitation could be used to recommend the OPDs of canola and maize. The study results provide an important reference for selecting optimal planting dates of staple crops and adapting to warming and drying climate for single cropping systems in rainfed regions. • Optimal planting date (OPD) varied among crops and regions. • Maize, canola, oil sunflower have earlier OPD than oats, potato, edible sunflower. • Oats, potato, and canola have higher drought-resistance than other three crops. • Precipitation and temperature before planting could be used to recommend OPD.

Crop modeling defines opportunities and challenges for drought escape, water capture, and yield increase using chilling-tolerant sorghum.

Many crop species, particularly those of tropical origin, are chilling sensitive, so improved chilling tolerance can enhance production of these crops in temperate regions. For the cereal crop sorghum (Sorghum bicolor L.), early planting and chilling tolerance have been investigated for >50 years, but the potential value or tradeoffs of this genotype × management change have not been formally evaluated with modeling. To assess the potential of early planted chilling‐tolerant grain sorghum in the central US sorghum belt, we conducted CERES‐Sorghum simulations and characterized scenarios under which this change would be expected to enhance (or diminish) drought escape, water capture, and yield. We conducted crop growth modeling for full‐ and short‐season hybrids under rainfed systems that were simulated to be planted in very early (April), early (May 15), and normal (June 15) planting dates over 1986–2015 in four locations in Kansas representative of the central US sorghum belt. Simulations indicated that very early planting will generally lead to lower initial soil moisture, longer growing periods, and higher evapotranspiration. Very early planting is expected to extend the growing period by 20% for short‐ or full‐season hybrids, reduce evaporation during fallow periods, and increase plant transpiration in the two‐thirds of years with the highest precipitation (mean > 428 mm), leading to 11% and 7% increase grain yield for short‐ and full‐season hybrids, respectively. Thus, in this major sorghum growing region, very early and early planting could reduce risks of terminal droughts, extend seasons, and increase rotation options, suggesting that further development of chilling‐tolerant hybrids is warranted.

Selection for Grain Yield Under Normal and Late planting Dates Conditions in Durum Wheat (Triticum turgidum L. var. durum)

The current investigation was conducted at Shandaweel Agric. Res. Station, Sohag governorate, Egypt during 2018/2019 to 2020/2021 seasons. Pedigree selection of grain yield plant-1 was practiced independently from the F2 to F4 generations under normal and late planting dates. Evaluation was under both planting dates in the F4 generation. The phenotypic variance was slightly higher than the genotypic variance, and reduced from the F2 to F4 generation. Broad-sense heritability was 83.47 and 86.73% under normal planting compared to 88.22 and 89.03% under late planting after the first and second cycle of selection, respectively. The realized heritability was 37.75 and 40.63% under normal planting compared to 57.75 and 83.48% under late planting after cycle 1 and 2, respectively. The average observed gain of grain yield plant-1 after two cycles of pedigree selection was 12.59 and 25.33% from bulk sample and 7.45 and 2.69% from the better parent for normal planting selections, while it was 22.05 and 47.18% from bulk sample and 16.48 and 20.59% from the better parent for late planting selections, when the selected families were evaluated under normal and late planting conditions, respectively. The antagonistic selection increased the mean and decreased the sensitivity compared to the synergistic selection either evaluation was under normal or late planting conditions. Based on the path-coefficient analysis, number of spikes plant-1 had the greatest positive direct effect on grain yield plant-1 followed by number of kernels spikes-1 and 100-kernel weight in the base population and cycle two of selection under both planting dates.

Integrated Management of Haricot Bean Foliage Beetle in Northeastern Ethiopia

A field experiment was conducted to determine the integrated effect of planting dates, insecticides, and their interaction on the reduction of yield and yield related components of haricot bean caused by haricot bean foliage beetle damage at Sirinka Agriculture Research Center, Ethiopia. Planting dates were normal planting (NP) and late planting (10 days after normal planting) (LP), while insecticides comprised Apron star seed dressing (A) and without insecticide (WI). The combined analysis revealed that late planting combined with Apron star seed dressing (LPA) resulted in the highest yield (1223.7 Kg/ha). On the other hand, normal planting date without insecticide application (NPWI) gave the lowest yield (209.6 kg/ha) and the maximum yield loss (209.6%). The cost-benefit analysis showed that use of LPA gave by far better high net profit over control. Thus, LPA are recommended for haricot bean foliage beetle management in northeastern Ethiopia.

Cool temperature caused by late planting affects seed vigor via altering kernel biomass and antioxidant metabolism in cotton (Gossypium hirsutum L.)

Cotton in double cropping systems (rapeseed-cotton or wheat-cotton) is often late-planted and experiences a much longer period of cool temperature at the late growth stage, which impairs seed quality. A two-year field experiment with two planting dates (normal and late planting date) was conducted to investigate the effects of late planting on cottonseed vigor and its relationship with seed biomass accumulation and kernel antioxidant metabolism during seed development. With the delay of planting date and the increasing height of fruiting branches, the mean daily temperature during boll period decreased from 25.9 °C to 20.7°C. Meanwhile, the seed, kernel and vigor index decreased by 2.6–12.1%, 4.7–15.0% and 2.5–16.0% respectively. The direct path coefficient of growing degree days (GDD) and the indirect path coefficients via GDD for seed, kernel and vigor index were positive and high. Seed vigor was more sensitive to the change of kernel index than seed index and the cool temperature limited the accumulation of kernel biomass mainly via reducing the maximum velocity of kernel biomass accumulation (Vmax), which led to a significant decline in seed vigor especially in the late planting date. Under cool temperature caused by late planting, the time of the maximum activity for each H2O2-scavenging enzyme was postponed with their maximum activities being decreased, which caused slow reduction in the content of malondialdehyde and H2O2 content during the late stage of seed development. In addition, peroxidase (POD) had the closest correlation with cottonseed vigor compared with catalase, ascorbate peroxidase and glutathione reductase. Altogether, low seed vigor occurred in late planting could be attributed to the decreased kernel biomass and prolonged duration of oxidative damage on membranes caused by cool temperature. The GDD of boll period is valuable for estimating cottonseed harvesting time especially under late planting conditions and seeds with high POD activity are more tolerant to cool temperature.

Blend response of four Egyptian cotton population types for late planting stress tolerance

BackgroundThis study was conducted to investigate the effect of heterogeneity and heterozygosity on lint yield and fiber quality of Egyptian cotton for late planting stress tolerance. Lint yield was recorded in two planting dates among four cotton population types which included homozygous lines grown in pure stands, hybrids grown in pure stands, homozygous lines in blended stands, and hybrids grown in blended stands. Comparisons were made using trait means, blend response, and heterotic response. Stress susceptibility index (SSI) was calculated over planting dates.ResultsIn normal planting date, the results showed that means of lint yield for homozygous entries (population I and II) were greater than mean yields of heterozygous entries (population III and IV). In late planting date, the results showed that mean of lint yield for some homozygous entries was equal mean yields of heterozygous entries. Regarding the yield, there was no significant difference between inbreds and blend of hybrids. However, the heterozygous populations had a lower (SSI) and more tolerance for late planting than homozygous populations. In late planting date, the two parents G.90 × CB.58 and G.95 had lint yield equal to or greater than means of blends (heterozygous populations). Adding to the two blends of inbreds, [((G.91 × G.90) × G.80)] + [G.90 × CB.58] and [((G.83 × G.80) × G.89) × (G.83 × Deltabine 703)] + [G.90 × CB.58] had the highest lint yield included the best inbred (G.90 × CB.58) suggesting that blend performance was determined by inbred performance.ConclusionsCotton blends may not provide buffering against late planting date. Blend response or heterotic response increased with late planting. However, cotton yields can sometimes be increased through the blends. Blends were not better than inbreds, and blend response was not consistent among the blends. Using blends is not recommended to increase yields or tolerance for late planting, and homozygous population’s cultivars could result in increased yields relative to blends. Assuming an efficient method for producing homozygous population’s cultivars was available, homozygous populations should be a viable option for commercial production to decrease observed losses in late planting date conditions.

Effect of selenium foliar application on oil yield, fatty acid composition and glucosinolate content of rapeseed cultivars under late-season thermal stress

To determine the possible protective and enhancer role of selenium foliar application on oil yield, fatty acid composition and glucosinolate content of rapeseed cultivars under late-season thermal stress, a factorial split-plot experiment based on randomized complete block design with three replications was carried out in Karaj, Iran during the two growing seasons 2014–2015 and 2015–2016. Three sowing dates (Oct. 7 as normal planting date), (Oct. 17 as semi-late planting date), (Oct. 27 as late planting date) and two selenium foliar application (non-application as control and sodium selenate as foliar application) were factorially randomized to main plots, and rapeseed cultivars were allocated to sub-plots. Plant materials were six cultivars including three hybrids and three Iranian open pollinated varieties. Late-season thermal stress caused by late planting date reduced oil yield, oil content, oleic acid, linoleic acid, palmitic acid and increased linolenic acid, erucic acid and glucosinolate content of investigated cultivars. The results of this study demonstrated that the highest amount of oil yield, oil content, oleic acid, linoleic acid, palmitic acid and the lowest amount of erucic acid and glucosinolate content were observed in L72 cultivar in both control and selenium application treatments. This study provided new important findings about the supportive and enhancer role of selenium in the form of sodium selenate on quantity and quality of oil in rapeseed plant.

Shifting planting date of Boro rice as a climate change adaptation strategy to reduce water use

Suitable adaptation strategies for dry season Boro rice cultivation under future climate change scenarios are important for future food security in Bangladesh. This study assessed the effect of shifting trans−/planting date of dry season Boro rice as an adaptation strategy, with focus on water requirements under future climate scenarios. Potential crop water requirement, effective rainfall and irrigation requirement to satisfy crop evapotranspiration of Boro rice were estimated using CropWat 8.0 for early, normal and late planting dates for 2050s and 2080s. Future climate scenarios were constructed using five global circulation model (GCM) outputs for RCP 4.5 and 8.5 by statistical downscaling and bias correction. Number of days exceeding the threshold temperatures (maximum of 35 °C and minimum of 25 °C) was counted for critical period of Boro rice to understand compatibility of the changed planting dates. Results indicate that late planting can substantially reduce irrigation demand by increasing rainfall availability during Boro growth duration, but the option is very limited due to both day- and night-time heat stress. An early planting, on the other hand, accounts for high water demand but ensures suitable temperature during the critical growth stages of the crop. The normal planting dates show the possibility of day-time heat stress. So, late planting of temperature-tolerant cultivars or early planting of high-yielding varieties would be recommended based on local water availability. However, adjustment of the planting date is currently limited because high temperature-tolerant cultivars are not available in the study region.

Optimizing planting date and supplemental irrigation for potato across the agro-pastoral ecotone in North China

Abstract Adjusting planting date along with supplemental irrigation is widely used to improve potato yield in the agro-pastoral ecotone (APE) with high variability of limited rainfall in North China. Optimal planting date and supplemental irrigation time for potato differed greatly with climate and soil conditions, and were not fully investigated via field experiments. In this study, using APSIM-Potato model carefully calibrated and validated with two-years serial planting experimental data, the individual and coupled impacts of planting date and supplemental irrigation time on yield and water productivity (PWP) of potato were quantified across the APE. APSIM-Potato performed well in simulating phenology, leaf area index (LAI), soil water dynamics, biomass of potato, and also captured the trend in potato yields under different planting dates. Based on the long-term simulations from 1981 to 2010, the optimal planting dates were May 10 (local normal planting date), May 20 and May 30 in the eastern, middle and western APE, respectively. Yield and PWP of potato could be increased by 12.5% and 7.0% in the middle APE, 23.3% and 18.3% in the western APE respectively, under the optimal planting date compared with the local normal planting date under rainfed condition. Supplemental irrigation (8-55 mm) from rainwater harvesting could increase potato yield by 3.5-35.2%, 6.9-41.8%, and 9.0-50.8% respectively, in the eastern, middle and western APE. The corresponding PWP could be enhanced by 1.2-22.7%, 6.7-30.8% and 4.5-33.7%, respectively. Combining the optimal planting date with better scheduling the maximal harvested rainwater could increase yield and PWP of potato by 36.8% and 23.4%, 69.2% and 49.2%, 64.3% and 48.8%, respectively for the eastern, middle and western APE, compared with the simulation results under the local normal planting dates and rainfed condition. The study suggested a large potential of increasing yield and PWP of potato across the APE by optimizing planting date and better scheduling the supplemental irrigation from rainwater harvesting.

Impact of high temperature on heterosis and general combining ability in spring canola (Brassica napus L.)

Canola is an extremely important commodity to the western Canadian economy. Annual or geographic fluctuations in yield due to heat stress can have a significant influence on total production. To increase the stability of canola yield, breeders need to select for increased heat tolerance in a reliable, repeatable, cost effective manner that represents commercial production conditions. Field experiments with 10 (5 maintainer and 5 restorer) inbreds and the 25 corresponding hybrids were conducted across 2 years with 2 locations per year. Each experiment had two planting dates (normal planting date and a late planting date). The experiments were designed to determine if: 1) planting date can be used as a proxy for heat stress; 2) heterosis can minimize the impact of heat stress; and 3) direct selection within a heat-stress environment improves genetic gain for heat-stress tolerance. Principal component analysis of the Tmax, Tmin, Tmean, soil moisture, daily light integral and yield were conducted. The resulting biplot analyses demonstrate that the temperature variables had a greater impact on yield than soil moisture or daily light integral and therefore planting date was identified as a successful proxy for heat stress. The heat-stress treatment caused a 23% mean reduction in seed yield (20% reduction within the hybrids and 25% reduction within the inbreds) indicating that heterosis can reduce the impact of higher temperatures on canola yield. The mean heat susceptibility index was 0.94 and 1.20 for the hybrids and inbreds respectively; further demonstrating that the hybrids were more heat tolerant than the inbreds. Analyses of the GCA for the inbreds shows 4 cross-over interactions between the two temperature treatments indicating that direct selection for heat tolerance will be necessary to increase the response to selection for this trait. Overall canola breeders interested in increasing heat tolerance need to consider utilizing planting date as a high-temperature treatment and cannot rely on indirect selection from experiments under optimal conditions.

Vulnerabilities and Adapting Irrigated and Rainfed Cotton to Climate Change in the Lower Mississippi Delta Region

Anthropogenic activities continue to emit potential greenhouse gases (GHG) into the atmosphere leading to a warmer climate over the earth. Predicting the impacts of climate change (CC) on food and fiber production systems in the future is essential for devising adaptations to sustain production and environmental quality. We used the CSM-CROPGRO-cotton v4.6 module within the RZWQM2 model for predicting the possible impacts of CC on cotton (Gossypium hirsutum) production systems in the lower Mississippi Delta (MS Delta) region of the USA. The CC scenarios were based on an ensemble of climate projections of multiple GCMs (Global Climate Models/General Circulation Models) for climate change under the CMIP5 (Climate Model Inter-comparison and Improvement Program 5) program, that were bias-corrected and spatially downscaled (BCSD) at Stoneville location in the MS Delta for the years 2050 and 2080. Four Representative Concentration Pathways (RCP) drove these CC projections: 2.6, 4.5, 6.0, and 8.5 (these numbers refer to radiative forcing levels in the atmosphere of 2.6, 4.5, 6.0, and 8.5 W·m−2), representing the increasing levels of the greenhouse gas (GHG) emission scenarios for the future, as used in the Intergovernmental Panel on Climate Change-Fifth Assessment Report (IPCC-AR5). The cotton model within RZWQM2, calibrated and validated for simulating cotton production at Stoneville, was used for simulating production under these CC scenarios. Under irrigated conditions, cotton yields increased significantly under the CC scenarios driven by the low to moderate emission levels of RCP 2.6, 4.5, and 6.0 in years 2050 and 2080, but under the highest emission scenario of RCP 8.5, the cotton yield increased in 2050 but declined significantly in year 2080. Under rainfed conditions, the yield declined in both 2050 and 2080 under all four RCP scenarios; however, the yield still increased when enough rainfall was received to meet the water requirements of the crop (in about 25% of the cases). As an adaptation measure, planting cotton six weeks earlier than the normal (historical average) planting date, in general, was found to boost irrigated cotton yields and compensate for the lost yields in all the CC scenarios. This early planting strategy only partially compensated for the rainfed cotton yield losses under all the CC scenarios, however, supplemental irrigations up to 10 cm compensated for all the yield losses.

Agro-Morphological Evaluation of Rice (Oryza sativa L.) for Seasonal Adaptation in the Sahelian Environment

In the Sahel zone of West Africa that extends from Senegal to Chad, temperatures can vary from less than 15 °C to 25 °C from November to February. These low temperatures affect the growth, development and yield of rice plants, and therefore constitute a major constraint to rice production in the Sahel. In order to identify rice varieties tolerant to cold stress at different developmental stages, a diverse set of 224 rice germplasm was evaluated for yield and yield-related traits in Ndiaye, Senegal, using three different sowing dates. The first sowing date (October 2010), was chosen so as to expose the rice plants to cold stress at the reproductive stage while the rice crop planted at the second sowing date (January 2011) experienced cold stress at the vegetative stage. The third sowing date (July 2011) was the normal planting date for irrigated rice in the Sahel and it served as the control date when the crop does not experience any cold stress throughout its growth cycle. Among the data collected, significant genetic variation was detected and genotype-by-environment interaction was also significant for the traits. At the vegetative stage, cold stress reduced tillering and plant vigor and delayed flowering but increased yield, whereas at the reproductive stage, aside from delaying flowering, cold stress also inhibited panicle exsertion and reduced panicle length, spikelet fertility, grain filling and strongly reduced yields. Principal Component Analysis and correlation analysis using agro-morphological traits helped to identify genotypes that were tolerant to cold stress at either the vegetative or the reproductive stage and the traits associated with high yield under cold stress at each of these stages. Our results can be used to develop cold tolerant rice varieties adapted to double cropping in the Sahelian zone of West Africa.

Effect of late planting and shading on cotton yield and fiber quality formation

Due to the competition of temperature and light resources during the growing season of double cropping system (cotton-rapeseed or cotton-wheat), cotton is generally late-germinating and late-maturing and has to suffer from the two factors of declining temperature and low light especially in the late growth stage. In this study, late planting (LP) and shading were used to fit the two-factor interaction stress, and to investigate their effects on lint yield and fiber quality formation. Two cotton cultivars, Kemian 1 and Sumian 15, were grown in the field in 2010 and 2011 at three planting dates with three shading levels. Among the three yield components, boll weight and boll number were the most sensitive indices to cool temperature and low light, respectively. The two-factor interaction of cool temperature and low light had a significantly effect on boll weight and lint percentage. Fiber length under shading increased throughout the extended duration of fiber elongation (T(Len)) in the normal planting date of 25-April (NPD25-April), and by the decline of maximum fiber elongation rate (V(Len)max) in the late planting dates (LPD). Fiber strength was reduced under the two-factor interaction of NPD25-April and shading due to the decrease of the duration and the mean strengthen rate of fiber strength growth periods. With further temperature decreasing, shading reduced strength mainly due to lower cellulose content and fiber biomass. In addition, compared to Sumian 15, Kemian 1 had higher V(Len)max and longer T(Mic) (data not shown) under the two-factor interaction of LP and shading, leading to longer fiber length and smaller decline of micronaire, and also had a lower decline in strength because of the smaller decline of fiber cellulose content and biomass. Therefore, cotton cultivar of Kemian 1 with a higher V(Len)max, longer T(Mic) and a less decline in cellulose content and biomass were more tolerant to the two-factor interaction.