Short-season Hybrids Research Articles

The environment, especially the minimum temperature, affects summer maize grain yield by regulating ear differentiation and grain development

Ear differentiation, grain development and their interaction with factors in the growing environment, such as temperature, solar radiation and precipitation, greatly influence grain number and grain weight, and ultimately affect summer maize production. In this study, field experiments involving different sowing dates were conducted over three years to evaluate the effects of temperature factors, average solar radiation and total precipitation on the growth process, ear differentiation, fertilization characteristics, grain filling and yield of summer maize varieties with different growth durations. Four hybrids were evaluated in Huang-Huai-Hai Plain (HHHP), China from 2018 to 2020 with five different sowing dates. The results showed that the grain yield formation of summer maize was strongly impacted by the environment from the silking (R1) to milking (R3) stage. Average minimum temperature (ATmin) was the key environmental factor that determined yield. Reductions in the length of the growing season (r=–0.556, P<0.01) and the total floret number on ear (R2=0.200, P<0.001) were found when ATmin was elevated from the emerging (VE) to R1 stage. Both grain-filling rate (R2=0.520, P<0.001) and the floret abortion rate on ear (R2=0.437, P<0.001) showed quadratic relationships with ATmin from the R1 to physiological maturity (R6) stage, while the number of days after the R1 stage (r=–0.756, P<0.01) was negatively correlated with ATmin. An increase in ATmin was beneficial for the promotion of yield when it did not exceeded a certain level (above 23°C during the R1–R3 stage and 20–21°C during the R1-R6 stage). Enhanced solar radiation and precipitation during R1–R6 increased the grain-filling rate (R2=0.562, P<0.001 and R2=0.229, P<0.05, respectively). Compared with short-season hybrids, full-season hybrids showed much greater suitability for a critical environment. The coordinated regulation of ATmin, ear differentiation and grain development at the pre- and post-silking stages improved maize yield by increasing total floret number and grain-filling rate, and by reducing the floret abortion rate on ear.

Maize planting date and maturity in the US central Great Plains: Exploring windows for maximizing yields

Region-specific guidelines for maize in the US Great Plains are needed to account for variability in farmer practices and inherent soil and climate differences. Therefore, it becomes critical to define environment tailored management strategies for maize crop to improve and sustain yields over time. The aims of this study were to: i) define homogenous maize yield environments classified as related to the maximum yield and its stability over time in the US central Great Plains region; ii) explore the combinations of planting date and hybrid maturity that lead to optimal yield for each of the previously defined homogenous maize yield environments; and iii) identify environments presenting different windows for maximizing yields (combinations of planting date by hybrid maturity). Hybrid maturity (growth cycle) by planting date combinations were explored at 70 sites within central and eastern Kansas and northern Oklahoma (herein defined as the US central Great Plains region) using 30 years of historical weather data. In addition to the analysis of an extensive maize field dataset, a crop growth model, Agricultural Production Systems Simulator (APSIM), was utilized to evaluate the crop yield and phenology of all hybrid maturity by planting date combinations to define environment tailored management strategies. The simulated yields were spatially clustered based on attainable yield and stability over time to delimit more homogeneous productivity environments. Overall, greater yields were attained with long-maturing hybrids (comparative relative maturity, CRM, 101 and 115). Delaying the planting date from April to mid-May decreased yield in eastern environments. Moreover, late planting maintained yields and increased stability in central environments. For central Kansas and Oklahoma, anticipation of physiological maturity date (3–16 days) with reduced yield penalties (<5%) were possible by using short-season hybrid maturities (CRM 85). Future scenarios for intensification could be explored in those environments presenting more windows for maximizing yields, either with early planting and harvest dates or via late planting providing time for a short crop before maize. Adoption of more region-specific guidelines for maize management could help to optimize yield and its stability over time and seek further opportunities to diversify risk and intensify our current maize-based farming systems in the US central Great Plains.

Comparative analysis of prospect corn varieties productivity under high-risk farming Amur river region area

The article presents the results of the results of the study of corn hybrids of various ecological and geographical origin according to economic traits. The research was carried out during 2019-2021 in the nursery of the competitive variety trial of the fodder production department on the experimental plot of vegetable rotation of the Far Eastern Agricultural Research Institute (FEARI) by the method of agro-climatic analogues as applicable to the extreme conditions of the Khabarovsk territory. The targets of research were 28 maize hybrids, 16 of which were selected by FEARI. The goal of research is сomparative assessment of the productivity of promising corn hybrids in conditions of risk farming zone in the Amur river region. The studied hybrids were divided into 2 groups: short-season hybrids (FAO - 150-199), 13 samples. The standard is the local selection Birsu hybrid. 2. middle-early hybrids (FAO - 200-299), 15 samples. The standard is released in the Khabarovsk territory Moldavian 215 SV hybrid. On average during the research period the grain productivity of most of the samples in the group of short-season hybrids didn’t exceed the characteristics of standard hybrid. Only Birsu (2-cob) hybrid stood out (+12.4 dt/ha). In terms of herbage and cob productivity almost all hybrids exceed the standard values (Birsu - 194,8; 106,6 dt/ha) by 9.7-126.2 and 9.0-29.49 dt/ha respectively. In the group of middle-early hybrids the Porumben 295 ASV x fertile restorer hybrid stood out. In terms of grain, herbage and cob productivity it exceeded the standard hybrid Moldavian 215 (59.7, 256.9, 110.4 dt/ha) by 31.7, 113.7 and 59.2 dt/ha respectively. Based on the research findings the selected by FEARI Alitet 2 advantageous hybrid was marked out. In terms of herbage productivity it exceed Birsu hybrid by 54.3% and in terms of cob productivity - by 26,1%. The hybrid is transferred to the state variety testing.

PSX-A-3 Characterization of Short-Season Hybrid Corn Stover and Barley Greenfeed Components Through in Vitro Digestibility and Methane Production

Abstract This study compared the nutrient composition, in vitro methane production, and dry matter (DM) and fiber disappearance of barley greenfeed (seed heads, SEED; leaves, BLEAF; and stems, STEM) and short-season high-moisture corn stover (cobs, COB; leaves and husks, CLEAF; and stalks, STALK) to wheat straw (STRAW). Each plant component was analyzed for DM and neutral detergent fiber corrected for organic matter (aNDFom). Plant components were incubated in in vitro batch cultures for 30 h during which total gas production and methane were measured. Incubation residues were analyzed for DM and aNDFom. The aNDFom (% of DM) was different (P&amp;lt; 0.01; SEM = 1.64) amongst treatments: COB (82.1) = STRAW (75.2) = STALK (72.8) = CLEAF (69.4) &amp;gt; STEM (52.5) = BLEAF (50.4) &amp;gt; SEED (39.1). The DM disappearance (% of DM) of barley components was the greatest (P&amp;lt; 0.01; SEM = 1.734; BLEAF = 60.98, STEM = 57.15, and SEED = 56.52), followed by CLEAF (48.15) and STALK (40.47), but STALK did not differ from the least digestible components of COB (37.21) and STRAW (35.82). Disappearance of aNDFom (% of aNDFom) was greatest (P&amp;lt; 0.01; SEM = 1.734) for BLEAF (63.27), then CLEAF (53.40) and SEED (45.65), but the other components (COB = 44.77, STALK = 44.17, STEM = 42.93, and STRAW = 42.57) were lowest and did not differ from SEED. A difference in methane production (mL/g of DM digested) was observed (P&amp;lt; 0.01; SEM = 1.392) in the following manner: COB (52.07) = STEM (51.04) = STRAW (47.88) = SEED (47.43) &amp;gt; BLEAF (40.83) = CLEAF (38.20) = STALK (36.89). These data provide fiber digestibility coefficients and methane production by plant components and confirms that fiber content is inversely related to DM digestibility for barley and corn components at grain harvest.

Comparative Yield and Photosynthetic Characteristics of Two Corn (Zea mays L.) Hybrids Differing in Maturity under Different Irrigation Treatments

Effective irrigation strategies are of great significance for improving crop yields. There is an increasing concern that short-season corn hybrids are gradually being encouraged to plant in the North China Plain (NCP) with the development of mechanized grain harvesting, but the photosynthetic characteristics and productivity of short-season hybrids are not well documented. The objective of the study was to investigate the effects of different irrigation treatments on photosynthetic characteristics, dry matter accumulation (DMA) and photo-assimilate translocation (PAT/PT), grain yield (GY) and water productivity (WP) of two corn hybrids differing in maturity. In the experiment plots under the rainout shelter facility, short-season hybrid Denghai518 (DH518) and medium- and full-season hybrid Denghai605 (DH605) were grown under three irrigation levels (severe water stress, T1; mild water stress, T2; and non-stress, T3) by two irrigation methods (flood irrigation, FI; surface drip irrigation, SDI) in 2020 and 2021. The results indicated that non-stomatal limitation (NSL) was the main factor leading to the reduction in photosynthesis during the reproductive stage. Severe water stress significantly decreased net photosynthetic rate (Pn) and chlorophyll soil-plant analysis development (SPAD) value, resulting in lower DMA and GY. The contribution rate of vegetative organ photosynthate before flowering (CRP) decreased with the irrigation levels increasing. DMA, GY and WP of SDI increased by 16.23%, 21.49% and 51.31%, respectively, compared to FI. The yields of DH518 were 7.22% lower than those of DH605. The WP penalty for DH605 was attributed to a relatively larger ET. It suggested that applying the optimum irrigation level (T3) under SDI could increase DMA, GY and WP of summer corn in the NCP.

Nitrogen and Phosphorus Balances Vary at the Whole-Farm, Field, and Within-Field Scales

A field nutrient balance (supplied minus harvested) can be an effective, end-of-season management evaluation tool. However, development of guidance for balance-based management requires knowledge of variability in balance inputs. To contribute to development of such guidelines, we evaluated the impact of corn silage hybrid selection, nutrient management, and growing conditions on field nitrogen (N) balances and documented variability in N and phosphorus (P) balances at the whole-farm, field, within-field levels. Variability in N removal among hybrids was evaluated using hybrid trials (5 locations, 4 years each). Variability in farm and field balances (4 farms, 2 years each) and within-field balances (2 farms, 2 years each) was assessed as well. Nitrogen supply comprised soil N (soil type-specific book values), rotation N, past manure N, and current year N (fertilizer and/or manure). Total N balances included all current year manure N while available N balances considered only plant-available N from manure. Phosphorus balances were derived as total P applied minus P harvested. Yield explained 81% of the variability in N uptake across hybrids. Nitrogen uptake intensity (NUI; N uptake per unit of yield) varied across locations and years, averaging 4.3 ± 0.1 kg N/Mg for short-season hybrids [≤95 days-to-maturity (DTM)] vs. 4.1 ± 0.1 kg N Mg−1 for longer-season hybrids. Whole-farm N balances ranged from 139 to 251 kg N ha−1 for total N and 43 to 106 kg N ha−1 for available N. Phosphorus balances ranged from 28 to 154 kg P ha−1. Balances per field ranged from −8 to 453, −66 to 250 kg N ha−1, and −30 to 315 kg P ha−1 for total N, available N, and total P, respectively, while within-field balances showed even larger ranges. We conclude that (1) variability in corn silage N and P balances at field and within-field scales and across year is large, emphasizing the need for field and within-field (where feasible) evaluation tools and management options, and (2) feasible limits for N balances should include both total and available N.

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.

Responses of maize hybrids with contrasting maturity to planting date in Northeast China

Maize sowing in semi-humid region of Jilin province is often delayed beyond the optimum planting time window because of soil water stress typically occurring before or during the planting season. Research was conducted at Lishu city, in Jilin province from 2009 through 2010 to determine the responses of maize hybrids with contrasting maturity to planting date. Three popular hybrids with contrasting different maturity, short-season hybrid Jidan27, mid-season hybrid Xianyu335, and full-season hybrid Zhengdan958 were planted in early May and mid-May and thinned to populations of 67,500 plants ha−1. The results showed that durations from emergence to silking stage for all the hybrids consistently shortened as the planting delayed, but interaction effects of hybrids, planting date and year existed for the duration of silking to physiological maturity stage. The longer maturity hybrid usually had grain yield advantage over earlier maturity hybrid when planting at early May, but the earlier maturity hybrid often showed a greater yield than longer maturity hybrid when planting was delayed. The highest yield occurred at the treatment combination of the mid-season hybrid and delayed planting date, and the shorter season hybrid typically showed stable and higher grain yield across planting dates. Changes in grain volume per unit of land area among hybrids and planting date treatment combination were consistent with the changes in grain yields, indicating that the yield is determined usually by the sink capacity. Further research is needed to evaluate the effects of hybrids maturity and planting date on maize under different planting densities.

Норма и стабильность реакции раннеспелых гибридов кукурузы на условия вегетации

Полевые опыты проведены в 20162018 годах на опытных полях ВНИИ кукурузы в п. Пятигорский Предгорного района Ставропольского края и в Институте агроэкологии филиале Южно-Уральского ГАУ в с. Миасское Красноармейского района Челябинской области. Цель исследований изучить потенциал урожая раннеспелых гибридов кукурузы и уборочную влажность зерна в разных климатических зонах, выявить гибриды, гарантирующие стабильно высокий урожай зерна в условиях Южного Урала. Одной из важнейших экологических особенностей кукурузы является её широкая норма реакции на изменение условий среды, показателем проявления которой выступает пластичность и стабильность. Было проведено изучение основных хозяйственно ценных показателей девяти раннеспелых гибридов кукурузы трёх селекционных учреждений РФ при оптимальном сроке посева в двух географических точках (Северо-Кавказском и Уральском регионах РФ). Анализ нормы и стабильности реакции гибридов кукурузы по урожаю зерна на условия вегетации позволил отнести все изучаемые гибриды к среднепластичным. Значение нормы линейной реакции (r 0,71) свидетельствует об усилении отзывчивости гибридов на улучшение условий среды. Низкостабильными оказались только два гибрида: Машук 150 МВ и Ладожский 148 СВ. Остальные гибриды относятся к высокостабильной группе. Экологическая стабильность реакции слабо связана с урожаем зерна (r 0,26). Высокоурожайными на Южном Урале оказались гибриды кукурузы Уральский 150 и Обский 140 СВ. Гибрид кукурузы очень раннего срока цветения Кубанский 101 СВ был самым низкоурожайным и низкорослым в обоих пунктах. Лучший гибрид кукурузы для условий Южного Урала Уральский 150: при среднем урожае зерна за 3 года 6,5 т/га его уборочная влажность составила 31,7. Field trials took place in 20162018. The aim to select the best short-season maize hybrids for the South Urals and evaluate their yield potential as well as grain moisture content at harvest under different environmental conditions. Maize has a wide range of responses to environment defining its plasticity and stability. Economically important traits of nine short season maize hybrids obtained from three Breeding Institutions were analyzed in the North Caucasus and Ural regions of Russia under optimal seeding date. Hybrid yields showed medium variation as a response to growth conditions. Linear reaction norm model (r 0.71) represented sensitivity increase to improved conditions. Mashuk 150 MV and Ladozhskiy 148 SV hybrids were the most sensitive to environmental changes. Other hybrids had similar performance across different environments. Low trait variation under different conditions affected grain yield insignificantly (r 0.26). Uralskiy 150 and Obskiy 140 SV had high productivity in the South Urals. Extra short-season Kubanskiy 101 SV hybrid showed the lowest productivity and height at both locations. Uralskiy 150 hybrid was the most productive in the South Urals: for 3 years its grain yield amounted to 6.5 t ha-1, grain moisture content at harvest 31.7.

Sunflower olein hybrides resistant to parasites

New hybrids of the first generation of sunflower of three ripeness groups with a high content of oleic acid in oil have been bred at the Federal State Budget Scientific Research Institute of the South-East region. A study of these hybrids in the conditions of the Saratov region in 2017–2018, conducted as a competitive varietal test, showed that new hybrids of the first generation of sunflower with a record oleic acid content in oil were obtained: early-ripening hybrid PG 784 - 79.0%, short-season hybrid PG-815 - 85.0%, mid-season hybrid PG-802 - 82.2%, which is 8.3-14.3% more than previous hybrids. The maximum harvest of oleic acid per unit area in the best early ripening hybrid of PG 784 was 1.06 t/ha, in the best short-season hybrids PG-812, PG-814 and PG-815 –1.02 t/ha, in the best mid-ripening hybrid PG-802 - 1.14 t/ha. It has been experimentally proved that, in the Saratov region it is possible to breed early-ripening, short-season and mid-ripening hybrids of the first generation of sunflower with an oleic acid content in oil of more than 80% and harvesting of oleic acid from a unit area of more than 1 t/ha.&#x0D;

Assessing planting date effects on seasonal water use of full- and short-season maize using SWAT in the southern Ogallala Aquifer region

A SWAT model equipped with an alternative auto-irrigation algorithm was used to evaluate the effects of planting date on hybrid corn yield and seasonal water use in the Texas High Plains. Research field data from the USDA-ARS Conservation and Production Research Laboratory at Bushland, TX and the Texas A&M AgriLife North Plains Research Field near Etter, TX were used for model calibration. A long-term weather data set was used to simulate continuous corn using five planting dates (15-April, 1-May, 15-May, 1-June, and 15-June) for both long- and short-season corn hybrids. Results suggested that delayed planting resulted in a reduction of seasonal water use for both hybrids. Reductions in seasonal irrigation between the 15-April and 15-June were 28 % and 31 % for long- and short-season hybrids, respectively, using an application depth of 25.4 mm. Corresponding reductions in yield were considerably less at 8.9 and 8.8 % for long- and short-season hybrids. Reduced irrigation was attributed to decreased temperature stress and lower evapotranspiration of the later growing season. However, simulation of long season corn for the 15-June planting resulted in late season cold temperature stress. Further analysis of 19.1 mm and 31.8 mm irrigation depths revealed the latter resulted in an average of 4.4 and 4.7 % reductions in seasonal irrigation for long- and short-season hybrids, respectively. Results from this assessment study suggest the delayed planting of corn may result in decreased irrigation while maintaining profitable yields, potentially reducing withdrawals from the Ogallala Aquifer in the Texas High Plains region.

Corn Forage Yield and Quality for Silage in Short Growing Season Areas of the Canadian Prairies

The development of short-season hybrids has made corn (Zea mays L.) silage (CS) production possible in cooler areas. This work aimed at determining biomass yield and nutritive quality of short-season corn CS hybrids. Six corn hybrids were grown in three years at four locations within the Canadian prairies with four field replications. Hybrids were harvested before occurrence of frost at a target dry matter (DM) content of 300 to 400 g kg−1. Corn heat units (CHU) from seeding to harvesting (CHUseed-harv) and water supply were recorded. Samples were analysed for nutrient content; i.e., DM, neutral detergent fiber (NDF), crude protein (CP), starch, and in vitro DM and NDF digestibilities (48 h incubation). Then, CHUseed-harv, water supply, whole plant DM, CHU rating of the hybrid, and cob percentage were assessed as predictors of nutrient content. Location, hybrid, and year affected nutrient composition and yield. Overall, CP and NDF were positively correlated (r = 0.48, p &lt; 0.01), but both were negatively correlated with DM yield (r = −0.63, −0.28, p &lt; 0.01) and starch (both r = 0.71, p &lt; 0.01). Within and among locations, CHUseed-harv differently affected nutrient composition and DM yield. However, DM yield was the most predictable factor (R2 = 0.86) with CHUseed-harv being the strongest contributor (48%) to the overall variability, followed by water supply (23%). Whole plant DM and CHUseed-harv were also good predictors of starch (R2 = 0.54). This work showed the high variability of biomass yield and nutritive quality of short-season CS hybrids grown in Northern areas.

In situ rumen degradation of kernels from short-season corn silage hybrids as affected by processing.

The objective of this in situ study was to evaluate the rumen degradability of kernels from short-season corn hybrids grown for silage in Western Canada (Lacombe, AB) and determine whether decreasing kernel particle size would enhance ruminal degradability in a similar manner for all hybrids. The study was a completely randomized design with 3 beef cows (replicates) and a 6 (hybrid) × 3 (particle size) factorial arrangement of treatments. Kernels were processed to generate three different particle sizes: large (2.3 mm), medium (1.4 mm), and small (0.7 mm). Processed samples were incubated in the rumen for 0, 3, 6, 12, 24, and 48 h using the in situ method and degradation kinetics of DM and starch were determined. Effective rumen degradability (ED) was estimated using a passage rate of 0.04 (ED4), 0.06 (ED6), and 0.08/h (ED8). Hybrids exhibited a range in whole plant DM content (23.7 to 25.0%), starch content (15.9 to 28.1% DM), kernel hardness (21.9 to 34.4 s/20 g) and density (3.57 to 4.18 g/mL), and prolamin content (8.24 to 11.34 g/100 g starch). Differences in digestion kinetics among hybrids were generally more pronounced for starch than DM. The hybrids differed in starch degradability (P < 0.05), with earlier maturing hybrids having lower A fraction, lower k d, and lower ED, with hybrid effects on ED being accentuated with faster passage rate. Kernel DM content (r = -0.85, -0.87), hardness (r = -0.89, -0.86), and density (r = -0.84, -0.85) were negatively correlated with ED4 and ED8 of starch, respectively, due mainly to decreased k d of fraction B. Reducing the particle size of kernels increased ED of starch due to increased A fraction and k d of the B fraction. A tendency (P = 0.09) for hybrid × processing effects for ED6 and ED8 indicated that processing had greater effects on increasing ED of starch for earlier maturing hybrids. We conclude that short-season hybrids that mature early may have lower ED of DM and starch and would benefit from prolonged ensilage time. Kernel processing during silage making is recommended for short-season corn hybrids as a means of enhancing rumen availability of starch.

Effects of feeding corn silage from short-season hybrids and extending the backgrounding period on production performance and carcass traits of beef cattle.

Corn silage (CS) acreage in western Canada continues to expand with CS being used increasingly in feedlot cattle diets where barley silage (BS) previously was the main forage fed. Our study evaluated the effects of increasing the amounts of CS in backgrounding (BKGN) diets on performance of cattle by 1) replacing BS with early-maturing CS, 2) increasing the proportion of CS in the diet, and 3) extending the BKGN duration. A total of 160 steers (mean BW ± SD; 272 ± 22.4 kg) were used in a completely randomized design. Steers were assigned to 16 pens and fed BKGN diets (4 pens per diet) that contained 60% BS (DM basis; CON), 60% CS (60CS), 75% CS (75CS), or 90% CS (90CS) until reaching a mean pen BW of either 380 (SBKGN) or 430 ± 15 kg (LBKGN) with 2 pens per treatment. All steers were finished (FIN diet; 9% CS, 86% barley grain, and 5% supplement) to an equal-BW end point (700 ± 15 kg LW). During BKGN and FIN phases, DMI, ADG, and G:F were measured for all pens. Carcass data also were collected. No BKGN diet × duration interactions were statistically significant (P ≥ 0.412) for most production measures. As dietary CS content was increased during BKGN, DMI and ADG decreased (quadratic; P ≤ 0.003). There also was a tendency (P = 0.078) for a decrease in G:F at the highest level of CS. As expected, LBKGN steers took longer (105 vs. 71 d; P = 0.001) than SBKGN steers to reach the BKGN target end weight. In addition, as a result of their heavier weight at the beginning of FIN, LBKGN steers also had a higher DMI (11.6 vs. 11.0 kg/d; P = 0.045) than SBKGN steers. However, no carryover effects (P ≥ 0.354) of BKGN diet on DMI, ADG, and G:F were significant during the FIN phase. Similarly, the BKGN diet and duration had no effect (P ≥ 0.219) on carcass traits including HCW, dressing percentage, and quality grade. However, we detected an interaction between BKGN diet and duration on backfat thickness (P = 0.009); SBKGN steers that were fed 75CS during BKGN accumulated more backfat during FIN than LBKGN steers that were fed 75CS during BKGN, and because they were lighter at the beginning of FIN they took longer to reach 700 kg BW, their end point. In conclusion, dietary inclusion of CS (up to 90% of diet DM) in place of BS and extending the BKGN period had marginal effects on FIN performance or carcass traits in our study. Therefore, beef producers can make extensive use of early-maturing CS in growing cattle diets without compromising animal performance or carcass quality.

Modeling the response of maize phenology, kernel set, and yield components to heat stress and heat shock with CSM-IXIM

The available evidence suggests that the current increasing trend in global surface temperatures will continue during this century, which will be accompanied by a greater frequency of extreme events. The IPCC has projected that higher temperatures may outscore the known optimal and maximum temperatures for maize. The purpose of this study was to improve the ability of the maize model CSM-IXIM to simulate crop development, growth, and yield under hot conditions, especially with regards to the impact of above-optimal temperatures around anthesis. Field and greenhouse experiments that were performed over three years (2014–2016) using the same short-season hybrid, PR37N01 (FAO 300), provided the data for this work. Maize was sown at a target population density of 5 plants m−2 on two sowing dates in 2014 and 2015 and on one in 2016 at three locations in Spain (northern, central, and southern Spain) with a well-defined thermal gradient. The same hybrid was also sown in two greenhouse chambers with daytime target temperatures of approximately 25 and above 35°C. During the nighttime, the temperature in both chambers was allowed to equilibrate with the outside temperature. The greenhouse treatments consisted of moving 18 plants at selected phenological stages (V4, V9, anthesis, lag phase, early grain filling) from the cool chamber to the hot chamber over a week and then returning the plants back to the cool chamber. An additional control treatment remained in the cool chamber all season, and in 2015 and 2016, one treatment remained permanently in the hot chamber. Two maize models in the Decision Support System for Agrotechnology Transfer (DSSAT) V4.6 were compared, namely CERES and IXIM. The IXIM version included additional components that were previously developed to improve the crop N simulation and to incorporate the anthesis-silking interval (ASI). A new thermal time calculation, a heat stress index, the impact of pollen-sterilizing temperatures, and the explicit simulation of male and female flowering as affected by the daily heat conditions were added to IXIM. The phenology simulation in field experiments by IXIM improved substantially. The RMSE for silking and maturity in CERES were 7.9 and 13.7days, decreasing in IXIM to 2.8 and 7.3days, respectively. Similarly, the estimated kernel numbers, kernel weight, grain yield and final biomass were always closer to the measurements in IXIM than in CERES. The worst simulations were for kernel weight, and for that reason, the differences in grain yield between the models were small (the RMSE in CERES was 1219kgha−1vs. 1082kgha−1 in IXIM). The greenhouse results also supported the improved estimations of crop development by IXIM (RMSE of 2.6days) relative to CERES (7.4days). The impact of the heat treatments on grain yield was consistently overestimated by CERES, while IXIM captured the general trend. The new IXIM model improved the CERES simulations when elevated temperatures were included in the evaluation data. Additional model testing with measurements from a wider latitudinal range and relevant heat conditions are required.

254 In vitro evaluation of short-season corn silage hybrids grown in central and southern Alberta, Canada, and harvested before or after frost: Nutrient content, degradability and enteric methane emission

254 In vitro evaluation of short-season corn silage hybrids grown in central and southern Alberta, Canada, and harvested before or after frost: Nutrient content, degradability and enteric methane emission

1441 Use of short-season hybrids may enable greater use of corn silage in western Canadian feedlot diets without decreasing animal performance

1441 Use of short-season hybrids may enable greater use of corn silage in western Canadian feedlot diets without decreasing animal performance

Respuestas correlacionadas para el rendimiento en la selección de híbridos de maices precoces subtropicales.

With the aim of designing selection criteria to identify the described genotypes with short vegetative period and longer grain-filling period without increasing the total growing cycle of the genotype. The information generated during 1995 at six locations in the subtropical region of Mexico was used. A serie of six experiments, integrated with a group of subtropical hybrids derived from a diallel between a group of elite tropical and subtropical inbred lines from CIMMYT, were evaluated in collaboration with INIFAP and the seed industry. In the combined analysis of six environments, early hybrids with a grain yield of 8.0 t/ha were identified; those hybrids were 14 days earlier to reach physiological maturity than the control check which yielded 7.4 t/ha. The genotypes with lower yields showed a short grain filling period compared to the vegetative period. Correlations among yield vs. days to physiological maturity, grain-filling period and the index calculated by dividing the between grain-filling /days to physiological maturity were 0.47, 0.53 and 0.41, respectively. This indicate an intermediate association between these traits; also, a high correlation values were observed between grain yield vs. plant and ear hight. The correlation between yield vs. days to silk and days to pollen shed were not significant. General combining ability (GCA) and specific combining ability (SCA) effects were significant for yield, days to silk and grain-filling period. Sufficient variation was observed to allow for the selection of genotypes with short vegetative periods and longer grain filling periods. The effects of GCA and SCA for grain-filling period suggest that this trait is an important criterion to select parents for producing short season hybrids.

Comparative yield and water use efficiency of two maize hybrids differing in maturity under solid set sprinkler and two different lateral spacing drip irrigation systems in León, Spain

The purpose of this study was to determine the technical viability of drip irrigation of maize in León, Spain, establishing the optimal parameters for crop cycle length and spacing between laterals and the feasibility of mild deficit irrigation. Water use efficiency (WUE) and irrigation water use efficiency (IWUE) were also determined, compared to the sprinkler method of irrigation widely used in the region. Treatments consisted of two irrigation methods (IMS: sprinkler irrigation, and IMD: drip irrigation) and two hybrid maturities (HMSS: short season, and HMMS: medium season). In sprinkler irrigation method, the irrigation level was 1.00ETc (crop evapotranspiration). Only for the drip irrigation treatments, subtreatments consisting of two lateral spacings (LS2: two rows, 110cm, and LS3: three rows, 165cm) and two irrigation levels (IL80: 0.80ETc and IL100: 1.00ETc) were studied. The mean grain yield was 17,551kgha−1 at 14% moisture content, with no significant difference between irrigation methods. The yields obtained with the medium season hybrid were significantly higher (18,191kgha−1) than those obtained with the short season hybrid (16,910kgha−1). No statistically significant differences were found between the yields obtained with the IL80 and IL100 treatments. Yields were slightly higher with the LS2 treatment than with LS3, although the level of statistical significance was very low (P=0.083). The mean WUE was 3.28kgm−3, and no significant differences were found between irrigation methods or crop cycle length. Highly significant differences were obtained between irrigation methods for IWUE: 3.38kgm−3 with IMS compared to 4.67kgm−3 with IMD, and reaching 5.17kgm−3 for IL80. The main conclusions of this study are that drip irrigation of maize is technically viable in the region and mild deficit irrigation does not reduce yields, obtaining yields equal to those achieved by sprinkler irrigation whilst presenting much higher irrigation water use efficiency.

Maize–planting date interaction and effect of Bt maize on European corn borer (Ostrinia nubilalis (Hubner) (Coleoptera: Crambidae) damage

A study was conducted to determine the influence of planting date and transgenic maize on maize yield following stalk injury by European corn borer, Ostrinia nubilalis (Hubner). Transgenic and non-transgenic maize hybrids with short- and full-season maturity were planted in late April, mid-May and early June from 2006 to 2008 in Ohio, USA. Maize stem tunnelling was significantly higher on non-transgenic maize and increased with delayed planting. Significantly higher yields were obtained from full-season than short-season hybrids when maize was planted early. The results suggest that when planting is delayed and an European corn borer population is known to cause economic damage in an area, selection of short-season hybrids with the Bt gene can be beneficial in controlling damage and improving yield.