High Plant Population Research Articles

Identifying Crowding Stress‐Tolerant Hybrids in Processing Sweet Corn

Improvement in tolerance to intense competition at high plant populations (i.e., crowding stress) is a major genetic driver of corn (Zea mays L.) yield gain the last half‐century. Recent research found differences in crowding stress tolerance among a few modern processing sweet corn hybrids; however, an investigation of interactions with other factors would reveal a deeper understanding of crowding stress tolerance in sweet corn. The objectives of this study were to (i) compare yield, recovery, and processor profitability of sweet corn hybrids grown under conditions of crowding stress, and (ii) determine if an interaction exists between N fertilization and hybrid on crop response to crowding stress. Twenty‐six hybrids were grown under suboptimal and supraoptimal N fertilization at 72,000 plants ha−1, a level beyond the optimal population of the most crowding stress‐tolerant hybrid. Results showed hybrid and N fertilization had no interactive effect on key variables of interest to the sweet corn processing industry, namely green ear mass, recovery, case production, and gross profit margin. Therefore, hybrid rankings were consistent whether the crop was N stressed or not. Relative to the poorest performing hybrid, the highest performing hybrid grown at an elevated population yielded 50% more green ear mass, 61% greater case production, and 71% higher gross profit margin. This work demonstrated a simple method to identify processing sweet corn hybrids with the best tolerance to crowding stress. Significant gains in sweet corn productivity may be realized by growing such hybrids at plant populations higher than currently used.

Forage Production and Population of Alfalfa Weevil (Hypera Postica) in Intercropping of Alfalfa and Sainfoin

Diversification of varieties or species within the same field can result in reduced pest population and increased yields. To study the forage production and alfalfa weevil (Hypera postica) population in alfalfa (Medicago sativa L.) and sainfoin (Onobrychis sativa) intercropping, a field experiment was carried out as a split-plot in time across 2 years (2010–12) with three replications. Treatments were: sole-cropping of alfalfa, sole-cropping of sainfoin, 50% alfalfa + 50% sainfoin as one row alternates, 50% alfalfa + 50% sainfoin as two row alternates, 75% alfalfa + 25% sainfoin, 25% alfalfa + 75% sainfoin, 10% sainfoin + 100% alfalfa, 20% sainfoin + 100% alfalfa, and 30% sainfoin + 100% alfalfa. Because of delayed emergence and growth of alfalfa in the first year, alfalfa weevil populations were monitored in the second year only. Sampling period was from April 9 to May 12, 2011. Five sampling dates were used. The results revealed that with increased ratio of alfalfa in mixed treatments, population of alfalfa weevil followed an increasing trend. In all treatment, pest population during the season showed a decreasing trend and reached zero level at the last sampling date. The highest value of dry yield was observed in 30% sainfoin + 100% alfalfa and the lowest value was obtained in sole-cropping of sainfoin and alfalfa. In both years, the highest values of land equivalent ratio were related to 30% sainfoin + 100% alfalfa treatment. We concluded that less competition between alfalfa and sainfoin caused a reduction in alfalfa yield losses from alfalfa weevil and higher plant populations in 30% sainfoin + 100% alfalfa compared to other combinations, increased forage production.

Industry‐Scale Evaluation of Maize Hybrids Selected for Increased Yield in Drought‐Stress Conditions of the US Corn Belt

ABSTRACTMaize (Zea mays L.) is among the most important grains contributing to global food security. Eighty years of genetic gain for yield of maize under both favorable and unfavorable stress‐prone drought conditions have been documented for the US Corn Belt, yet maize remains vulnerable to drought conditions, especially at the critical developmental stage of flowering. Optimum AQUAmax (Dupont Pioneer) maize hybrids were developed for increased grain yield under drought and favorable conditions in the US Corn Belt. Following the initial commercial launch in 2011, a large on‐farm data set has been accumulated (10,731 locations) comparing a large sample of the AQUAmax hybrids (78 hybrids) to a large sample of industry‐leading hybrids (4287 hybrids) used by growers throughout the US Corn Belt. Following 3 yr (2011–2013) of on‐farm industry‐scale testing, the AQUAmax hybrids were on average 6.5% higher yielding under water‐limited conditions (2006 locations) and 1.9% higher yielding under favorable growing conditions (8725 locations). In a complementary study, 3 yr (2010–2012) of hybrid‐by‐management‐by‐environment evaluation under water‐limited conditions (14 locations) indicated that the AQUAmax hybrids had greater yield at higher plant populations when compared to non‐AQUAmax hybrids. The combined results from research (2008–2010) and on‐farm (2011–2013) testing throughout the US Corn Belt over the 6‐yr period from 2008 to 2013 indicate that the AQUAmax hybrids offer farmers greater yield stability under water‐limited conditions with no yield penalty when the water limitations are relieved and growing conditions are favorable.

Decomposing maize yield gaps differentiates entry points for intensification in the rainfed mid-hills of Nepal

The central mid-hills region of Nepal is characterized by rainfed production systems where maize (Zea mays) is the principal crop during the monsoon (kharif) season. In general, maize yields in the hills are judged to be intractably low and few efforts have systematically assessed either the water-limited productivity potential or identified sensible entry points toward sustainable intensification that can be selectively matched to the needs and constraints faced by different types of farmers. This study combines field surveys, on-farm field experiments, and simulation modeling (DSSAT) to explore opportunities for closing maize yield gaps in these ecologies. Among surveyed households, the mean grain yield of maize under current farmer practice was 2.0tha−1 whereas good agronomic practices increased maize yields up to 6.5tha−1 (i.e. exploitable yield gap of 4.5tha−1). Recognizing that farmers rarely adopt full technology packages, the value of single agronomic interventions was also explored with all other management factors maintained as per prevailing farmer practice. Averaged across sites and two seasons, non-limiting fertilizer rates (175:60:60kgNPKha−1) increased grain yields by 1.8tha−1 followed by the use of hybrids (1.4tha−1), higher plant population (0.9tha−1), and improved weed control (0.9tha−1). These results were also reflected in changes to the economic performance of the system with gross margins increasing from a ‘farmer practice’ base of $202ha−1 (B:C=1.86) to $339ha−1 (B:C=2.14) with hybrid adoption, $454ha−1 (B:C=2.88) with higher plant population, $646ha−1 (B:C=2.52) with non-limiting fertilizer, and $611ha−1 (B:C=3.37) with careful weed control. Further gains in profitability were achieved with layered agronomic interventions, which increased gross margins to $857 and $763ha−1 (B:C=2.95 in both) in conventional tillage (CT) and minimum (strip tillage; ST) systems, respectively. Divergence between grain yield gains and economic performance criteria highlights the importance of considering both perspectives. For resource-poor households, maintaining optimal plant population can increase B:C by more than 50% with small investments ($7ha−1). Simulation results also suggest that additional potential productivity advantages are achievable with timely planting (e.g. 19% higher mean yield for short duration hybrid with less inter-annual variability). Cultivation of longer duration hybrids can also increase yield potential over their shorter duration alternatives, although trade-offs with yield potential of the second crop in the rotation must be considered. These results highlight several pathways toward intensification in the hills of Nepal that have varying investment requirements, inferred risks, and implications for the different dimensions of sustainability and food security.

Performance evaluation of laser guided leveler

The study was conducted at Bangladesh Agricultural Research Institute (BARI) farm on clay loam soil during Rabi season of 2010-2011. The treatments consisted of laser land leveling (T1) and control (non-leveled) (T2). A preliminary field survey was done using staff gage. Initially a base station was established to dispense laser ray uniformly. The laser ray erected from base station guided the sensor of the stuff gage and the leveler. Elevation data was collected from the different points of the field and made an average. The maximum gage reading were 247.0 cm and the minimum gage reading was 219.2 cm. Average gage readings of the laser leveled plot was 235.66 cm that was settled for auto adjustment. Therefore, huge amount of soils (16.46 cm high) was cut from the highest point and subsequently had to fill to the low points. Finally, an equal gage reading of 235.66 cm was observed after leveling the plot. The laser leveler (Leica MLS700) was used hitching with a TAFE tractor. The field was leveled with manual control initially and finally it was operated with auto adjustment. Two operators, 25 litter diesels and total 6 hours time were required during this leveling. Wheat was cultivated in leveled land (T1) and non-leveled land (T2). Laser leveling was insured for improvement in nutrient use efficiencies, option for precision farming, reduces weed problems, and improves uniformity of crop maturity. There was better distribution of water in leveled plot, which helped to reduce irrigation application time 1 hour. Due to uniformity of moisture content improved germination and crop establishment was found which reflected in higher plant population (239 m-2). Maximum yield (3.41 t ha-1) was obtained in T1 due to longer panicle (10.89 cm), more grain per plant (27.47) and 1000 grain weight (47.38 g) compared to yield of T2 (2.62 t ha-1). DOI: http://dx.doi.org/10.3329/ijarit.v4i2.22655 Int. J. Agril. Res. Innov. & Tech. 4 (2): 82-86, December, 2014

No-till strip row farming using yearly maize-soybean rotation increases yield of maize by 75 %

Development of agronomic practices that maximize the use of natural resources to improve soil health and crop productivity is critical for long-term sustainability of agricultural technologies. In Ontario, Canada, the most conventional maize production practice follows a 3-year rotation with soybeans and ploughing of the land before planting and after harvesting. This technology yields 8–10 t ha−1 of maize. We became aware of a long-term no-till strip row farming system developed by an Ontario grower where maize yields are double that of the average for the province. This study set out to identify what factors contribute to such a massive yield increase and the basis for this superior method of maize production. In a 2-year field study, we compared a variety of biotic and abiotic factors associated with yields at this highly productive site with those of two average yielding sites. The no-till strip row farming system grew maize and soybeans in alternate strips rotated yearly and had higher plant populations, better root architecture, higher plant biomass, and 75 % greater (18.35 t ha−1) grain yield compared to a nearby farm that used conventional production practices. About 21 % of the yield increase resulted from early planting, greater number of seeds planted, and healthier ears/seeds. The remaining 54 % increase was linked to larger ears, which we tentatively attribute to beneficial effects conferred by the microorganisms that develop in this unique agro-ecosystem. The average net return at the no-till site was estimated to be CDN (Canadian) $2000 ha−1, which was 400 % higher than the net returns of the conventional sites. The study concludes that no-till management where soil remains undisturbed when combined with yearly rotations of an appropriate legume crop, growing crops exactly on the same cropping rows every year, and optimization of plant density creates a sustainable technology for maximizing maize yields.

Cotton yield and fiber quality affected by row spacing and shading at different growth stages

Carbohydrate production and reproductive structure development in cotton (Gossypium hirsutum) depends on light availability, a determinant of cotton yield. Light availability is decreased by cloud cover or self-shading when cotton plants are grown in dense populations. The objective of this study was to evaluate the effects of shading during cotton growth and its interactions with plant row spacings on yield and fiber quality. Three independent experiments were conducted as follows: in Paranapanema (23°39′S; 48°58′W), cotton was planted in November in row spacings of 0.45, 0.75 and 0.96m; in Primavera do Leste (15°33′S; 54°11′W), planting was in January with at row spacings of 0.45 and 0.76m; and in Chapadão do Céu (18°38′S; 52°40′W), cotton was planted in February in rows spaced at 0.45 and 0.90 m. Plants were exposed to shading during the phenological stages B1 (floral bud), F1 (early flowering), PF (peak flowering) and 3OB (fruit maturity). In addition, there was one treatment without shade. There were no interactions of crop spacing with shading. Increasing plant population and shading both decreased net photosynthetic rate. The number of bolls m−2 increased with higher plant populations only when planting was delayed, and were not affected by shading. When cotton was planted in November and January, higher yields were obtained at 0.75/0.76m, but when planting was delayed to February, 0.45m resulted in higher yields with no effect on fiber quality. Shading for eight or ten days decreases boll weight and yields, but do not affect fiber quality. Cotton yield is the most decreased when shading occurs during flowering. These results may be used to build management strategies to minimize shading effects by adjusting cotton sowing time and plant density, by selecting cultivars with increased shade tolerance and by choosing an adequate irrigation period to improve yield.

Plant Growth, Fruit Yield and Mineral Content of Bottle Gourd (Lagenaria siceraria M) as Affected by Plant Density and Nitrogen Fertilizer

This experiment was carried out during two successive summer seasons of 2012 and 2013 on bottle gourdlandrace El-Arishy (Lagenaria siceraria M) at the Experimental Research Farm of the Faculty of Agriculture, SuezCanal University, Ismailia, Egypt to study the effect of plant density and nitrogen fertilizer on plant growth, yield andits components as well as mineral content. The obtained results showed that the low plant population (1750 plant perfad.) gave the highest shoot fresh weight, shoot dry weight, average fruit weight, average fruit length and nitrogencontent in shoots and fruits. However, the significant highest fruit yield and fruit number per faddan were associatedwith the high plant population (3500 plant per faddan). All previous mentioned parameters in addition to shoot and fruitphosphorus contents significantly improved by application of high nitrogen rate (20g/plant). Shoot and fruit potassiumand phosphorus contents were not affected significantly by plant spacing. Fruit potassium content did not affectsignificantly by nitrogen fertilizer. All the above mentioned parameters were significantly higher with the interactionbetween low plant population (1750 plant per fad.) was combined with high nitrogen rate (20g/plant), except fruit yield(ton/fad.) and fruit number which increased by the combination of high plant population with high nitrogen rate.Potassium content did not affect by the interaction between plant spacing and nitrogen fertilizer.

AMMI analysis to comprehend genotype-by-environment (G × E) interactions in rainfed grown soybean [Glycine max. (L)Merrill

The additive main effects and multiplicative interaction (AMMI) model was used to analysis the yield and yield component traits data of 25 soybean genotypes grown in three environments(Normal condition with rainfed condition, high plant population with rainfed condition and normal population with excess moisture). Main effects due to environments (E)and genotypes (G) were found significant for the all traits. The G × E interaction was significant for most of the traits, except days to 50% flowering, days to maturity and 100 seed weight (g). Gollob’s test declared two components, Principal Component Analysis1 (PCA 1) and PCA 2, statistically significant (P

Soybean Yield Potential Under Contrasting Maturity Groups, Plant Population and Soil Water Regimes in Eastern Uruguay

Soybean is the main crop in Uruguayan agricultural systems. Integrated crop management practices are critical to increase productivity while reducing climatic vulnerability in soils with restricted water holding capacity. The objective was to evaluate the impact of contrasting crop management practices and water regimes on crop yield potential. We conducted a three year (2012-2013, 2013-2014 and 2014-2015) field scale study on an Abruptic Argiaquoll at INIA Treinta y Tres, Uruguay. In each season, two experiments were set under contrasting water regimes: rainfed (RF) and supplementary irrigation (SI). Each experiment evaluated 4 Maturity Groups (MG): 5.0, 5.5, 6.1 and 6.8; and 4 Plant Populations (PP): 15, 25, 35 and 45 plants m-2. A RCB split plot design was used and analyzed using mixed models. The greatest productivity was obtained in 2012-2013 (4030 kg ha-1), 22% higher than the average of other seasons. No water regime effect on yield was observed in the first two seasons. In 2012-2013, no yield differences were observed between MG. However, 15 plants m-2 had 4.4% lower yield than other PP (4067 kg ha-1). In 2013-2014 no productivity differences were observed between PP, but MG 5.5 had 11 % higher yield than other MG (3271 kg ha-1). In 2014-2015, SI yield (3760 kg ha-1) was 1020 kg ha-1 higher than RF. SI received 105 mm of supplementary irrigation. In RF, 5.0 MG had a trend of higher yield (16%) compared to other MG (2608 kg ha-1) and 45 plants m-2 decreased yield by 6% compared to other PP (2754 kg ha-1). In SI, the greatest yield was obtained with MG 5.0 (3941 kg ha-1). The aggregate of data suggests that yield potential without water restrictions was 4000 kg ha-1 for most MG, with higher yields in high PP. However, under water limiting conditions in reproductive stages, high populations decreased yield. Water productivity reached 10 kg grain mm-1 applied, reflecting the positive impact of supplementary irrigation.

EFFECT OF PLANT POPULATION AND DISTRIBUTION ON YIELD AND YIELD COMPONENTS OF FIVE FABA BEAN GENOTYPES

Plant population density plays an important role on crop growth and yield as response to light penetration and photosynthesis rate. A field experiment was carried out at Sids Research Station, Agricultural Research Center (ARC), during two successive winter seasons, of 2012/13 and 2013/14. The objectives of this investigation was aimed to evaluate five faba bean genotypes namely Nubaria 1(large seeded cultivar), Giza 429, line 43130, E.19 (medium seeded types) in addition to the small seeded type Camolina. Plant densities were; a) 8 plants/m2 planted in single seeded hills spaced 20 cm on one side of 60 cm wide ridges, b) 17 plants/m2 planted in double seeded hills spaced 20 cm on one side of the ridges, c) 17 plants/m2 planted in single seeded hills spaced 20 cm on both sides of the ridges and d) 33 plants/m2 planted in double seeded hills spaced 20 cm on both sides of the ridges. Results indicated that, faba bean genotypes were significantly different in all studied characters. Nubaria 1 and E.19 genotypes had the tallest plants, respectively. The highest seed yield per feddan was obtained from Nubaria 1 cultivar, while the medium seeded line L-43130 produced the lowest seed yield per feddan over both seasons. Giza 429 (medium seeded cultivar) followed by Nubaria 1. Plant population of 17 plants/m2 in single seeded hills on both sides of the ridges produced highest seed yield per feddan over all genotypes. Concerning to the interaction between plant populations and faba bean genotypes, highest seed yield per feddan was obtained from the large seeded cultivar Nubaria 1 under the low plant population (8 plants/m2), while the medium seeded types i.e. Giza 429, L-43130 and E19 were more yielding under the third plant population (17 plants/m2 on both sides of the ridge). On the other hand, the small seed type Camolina produced highest seed yield per feddan under the high plant population (33 plants/m2). The interaction between faba bean genotypes and plant population had significant effects on all studied characters except number of days to flowering.

Evaluation of insecticides and application methods to protect onions from onion maggot, Delia antiqua, and seedcorn maggot, Delia platura, damage

Onion maggot, Delia antiqua (Meigen), and seedcorn maggot, Delia platura (Meigen), are important pests of spring-sown onions, Allium cepa L. Larvae of both species feed on developing epicotyls and roots of young onion plants often resulting in seedling mortality. Cultural controls used in combination with the insecticide chlorpyrifos are currently the standard practice for maggot control in the western USA. However, cultural controls are only partially effective and reliance on chlorpyrifos has several potential problems including future availability and development of resistance. Insecticides including clothianidin, imidacloprid, spinosad, and thiamethoxam were evaluated in California, USA in 2011–2013 to identify efficacious alternatives to chlorpyrifos. Some insecticides were applied in multiple ways including seed treatment, in-furrow application at planting, and rototiller incorporation prior to planting. Onion plant population, vigor, and yield were measured to assess insecticide efficacy. Maggots reduced onion plant populations by more than 65% of the seeding rate in the untreated controls. Seed treatments with spinosad or clothianidin + imidacloprid were the best alternative to chlorpyrifos for minimizing onion mortality from maggot feeding. Onions treated with both seed treatments had similar or higher plant populations and bulb yields compared to chlorpyrifos. The efficacy of spinosad was greatly improved when applied as a seed treatment compared to an in-furrow application at planting or when incorporated into the soil with a rototiller prior to planting. Spinosad seed treatment increased onion plant populations by 256%, 76%, and 853% compared to untreated controls in 2011, 2012, and 2013, respectively. Conversely, in-furrow and rototill-incorporated applications of spinosad were similar to the untreated control in terms of onion plant population and yield. Seed treatments with newer chemistries could provide an efficacious alternative to chlorpyrifos for protecting onions from maggot damage in western onion production systems.

Photoperiod and growing degree days effect on dry matter partitioning in Jerusalem artichoke

The effect of photoperiod and growing degree days (GDD) on dry matter and dry matter partitioning in Jerusalem artichoke was investigated during 2008-09 and 2009-10. Three Jerusalem artichoke genotypes (CN-52867, JA-89 and HEL-65) were planted in 15 day-intervals between with thirteen different dates (September 20 to March 20) at Khon Kaen University, Thailand. Jerusalem artichoke genotypes responded differently to varying planting dates for harvest index, shoot dry weight, leaf area, number of tubers and tuber size. Two genotypes, CN-52867 and JA-89, were significantly more productive on the planting date of 20 September and they also performed well on planting dates of 5 October to 20 March. Plant grown in long photoperiod with a higher number of GDD produced shoot dry weight rather than greater number of harvestable tubers, while short photoperiod induced high partitioning of assimilates to harvestable tubers. Jerusalem artichoke plants grown during short photoperiod were smaller and produced larger tubers than those grown during long photoperiod. Tuber yield was relatively unchanged across planting dates. Since Jerusalem artichoke during short photoperiod had smaller plants, growing Jerusalem artichoke at higher plant population with optimum density is highly recommended to increase tuber yield. The information obtained in this study is extremely important for Jerusalem artichoke production and breeding in the tropical agro-climatic conditions such as Thailand.

Soybean Yield Partitioning Changes Revealed by Genetic Gain and Seeding Rate Interactions

Soybean [Glycine max (L.) Merr.] yield has increased during the past century; however, little is understood about the morphological parameters that have contributed most to yield gain. We conducted field studies to determine relationships between genetic gain of soybean yield and seeding rate. The hypothesis was newer cultivars would express higher yield than older cultivars when grown in higher plant populations. A total of 116 soybean cultivars equally representing Maturity Groups (MGs) II and III released over the last 80 yr were evaluated at high and low seeding rates in Wisconsin, Minnesota, Illinois, and Indiana. Seeding rates were 445,000 and 148,000 seeds ha−1 resulting in 311,000 and 94,000 plants ha−1 (high and low, respectively). Seed yield was greater for the high seeding rate vs. low seeding rate throughout all cultivars and years of release, but the difference was larger in newer cultivars. The differences observed primarily came from an increased number of pods and seeds plant−1. However, newer cultivars grown in low seeding rates increased per plant yield linearly by 0.118 (± 0.02)x– 208.0 g plant−1, where x = year‐of‐release, which was three times greater than at the high seeding rate. The greater yield trend came from seeds produced on plant branches. Therefore, newer cultivars produce more compensatory yield on plant branches under lower plant populations than older cultivars, so over the last 80 yr there has been a diminishing response to the expected yield penalty from reduced plant density.

Nitrogen Level and Physiological Basis of Yield of Mungbean at Varying Plant Population in High Ganges River Flood Plain Soil of Bangladesh

A field experiment was conducted at the Regional Agricultural Research Station of Bangladesh Agricultural Research Institute, Jessore during early kharif season of 2009 and 2010 to observe the effect of nitrogen on the physiological basis of yield of mungbean at varying plant population. In the experiment, four nitrogen levels (N0, N40, N60 and N80 kg ha(-1)) were assigned in the main plots and three plant population (P30, P35 and P40 m(-2)) in the sub plots. The results revealed that mungbean showed better growth in N60 and N80 kg ha(-1) representing higher values of CGR, TDM, LAI and plant height while N40 exhibited intermediate growth. Again, growth of mungbean was better in higher plant population (35-40 m(-2)) representing higher values of growth parameters. Seed yield of mungbean was obtained the highest (1908 kg ha(-1)) associated with the highest No. of pods plant(-1) (29.98), seeds pod(-1) (10.41) and 1000-seed weight (37.70 g) in N40 kg ha(-1). Further, seed yield of mungbean was the highest (1919 kg ha(-1)) in plant population of 40 m(-2). In interaction, seed yield was the highest (1963 kg ha(-1)) in N40 kg ha(-1) with plant population of 40 m(-2). The effect of applied nitrogen on the seed yield of mungbean can be explained 78% (R2 = 0.78) by this function (Y = 1540.70+16.069x-0.173x2). The optimum nitrogen level was 46 kg ha(-1) by using the developed functional model and then the predicted seed yield of mungbean would be 1944 kg ha(-1).

Agronomic Response of Soybean Varieties to Plant Population in the Guinea Savannas of Nigeria

The agronomic responses of three contrasting soybean [Glycine max (L.) Merr.] varieties to plant populations were examined in two distinct agro‐ecological locations (at Samaru Zaria and Samaru‐Kataf), both in the Guinea savanna of northern Nigeria in 2009, 2010, and in 2011 growing seasons. Three soybean varieties: TGx1835‐10E, TGx1904‐6F, and TGx1448‐2E differing in maturity duration (early, medium, and late maturing, respectively), were evaluated at four plant populations (266,700, 333,300, 533,300, and 666,700 plants ha−1) using a split plot arrangement in randomized complete block design with three replications. The plant populations were the main plots, whereas varieties were subplots. The proportion of intercepted photosynthetically active radiation (IPAR) and leaf area index (LAI) increased with increasing plant population at both locations, indicating that high leaf area indices and high degree of canopy closure at higher plant population intercepted more light than the canopy at lower population and subsequently resulted in relatively high grain and fodder yields. At both locations, optimum plant populations ranged from 533,300 to 666,700 plants ha−1 across the years. The northern Guinea savanna location (Samaru Zaria) produced more pods m−2, grain yield, and fodder at higher plant populations than that at the southern Guinea savanna (Samaru‐Kataf). Varieties TGx1448‐2E and TGx1904‐6F intercepted higher proportion of IPAR had higher LAI and produced a greater number of pods m−2, seeds m−2, grain yield, and fodder than TGx1835‐10E at both locations in years of good rainfall. These data suggest that soybean yields in the Guinea savanna of northern Nigeria can be increased using higher plant populations than those currently recommended.

Effects of Sowing Date and Plant Population on Snap Bean (Phaseolus vulgaris L.) Growth and Pod Yield in Khartoum State

This study was conducted to find an optimum sowing date and plant population for bean cultivars suitable for export in Khartoum State. A field experiment was conducted in winter in 2011-2012, at the College of Agricultural Studies, Sudan University of Science and Technology, Sudan. Two sowing datesS₁ and S₂ (7^th and 26^th of November, respectively) and six plant populations obtained by three plant spacing (10, 15 and20cm plant spacing) and two planting densities (2 and 3 plants/hill) on 70cm ridges were tested in completely randomized block design in four replications. The results showed that early sowing date (S₁) had positive effects on both growth and pod yield and quality compared to late sowing (S₂), irrespective of plant population. Increasing of plant population increased plant height but decreased pod yield. The highest pod yield (105.9 g) was obtained at early sowing (S₁) by 2plants/hill and 20cm plant spacing which was almost double that (56.3 g) obtained at the same plant population at late sowing (S₂). Pod yield /ha was higher at S₁ at all plant population than S₂. However, the highest pod yield/ha was obtained at S₁ by the highest plant population (3plant/ hill at 10cm spacing) and the lowest at S₂ by the lowest plant population (2plants/hill at 20cm spacing). Moreover, all pod quality parameters were positively affected by planting density irrespective of plant spacing. It could be concluded that for optimum green pod yield and quality of beans for export it should be sown as early as the first week of November at 2 plant/hill and 10 cm or 3 plants/hill at 15cm plant spacing on 70cm ridges in Khartoum State and areas of similar conditions.

Plant population differentiation and climate change: responses of grassland species along an elevational gradient

Mountain ecosystems are particularly susceptible to climate change. Characterizing intraspecific variation of alpine plants along elevational gradients is crucial for estimating their vulnerability to predicted changes. Environmental conditions vary with elevation, which might influence plastic responses and affect selection pressures that lead to local adaptation. Thus, local adaptation and phenotypic plasticity among low and high elevation plant populations in response to climate, soil and other factors associated with elevational gradients might underlie different responses of these populations to climate warming. Using a transplant experiment along an elevational gradient, we investigated reproductive phenology, growth and reproduction of the nutrient-poor grassland species Ranunculus bulbosus, Trifolium montanum and Briza media. Seeds were collected from low and high elevation source populations across the Swiss Alps and grown in nine common gardens at three different elevations with two different soil depths. Despite genetic differentiation in some traits, the results revealed no indication of local adaptation to the elevation of population origin. Reproductive phenology was advanced at lower elevation in low and high elevation populations of all three species. Growth and reproduction of T. montanum and B. media were hardly affected by garden elevation and soil depth. In R. bulbosus, however, growth decreased and reproductive investment increased at higher elevation. Furthermore, soil depth influenced growth and reproduction of low elevation R. bulbosus populations. We found no evidence for local adaptation to elevation of origin and hardly any differences in the responses of low and high elevation populations. However, the consistent advanced reproductive phenology observed in all three species shows that they have the potential to plastically respond to environmental variation. We conclude that populations might not be forced to migrate to higher elevations as a consequence of climate warming, as plasticity will buffer the detrimental effects of climate change in the three investigated nutrient-poor grassland species.

Crescimento do abacaxizeiro 'vitória' irrigado sob diferentes densidades populacionais, fontes e doses de nitrogênio

Com o objetivo de avaliar o crescimento do abacaxizeiro 'Vitória' irrigado, submetido ao aumento da densidade populacional, e doses de N na região norte de Minas Gerais, foi instalado um experimento em esquema fatorial 5 x 4 x 4, correspondendo a cinco doses de N (0; 5; 10; 15 e 20 g planta-1), quatro populações de plantas (51.282; 76.923; 90.909 e 126.984 plantas ha-1) e quatro épocas de avaliação (270; 360; 450 e 540 dias após o plantio - DAP), utilizando ureia ou esterco bovino como fonte de N. Aos 540 dias após o plantio - DAP (época de indução floral), foi avaliado o efeito das fontes de N por meio do fatorial 2 x 5 x 4, que consistiu em : duas fontes N (ureia e esterco bovino), cinco doses de N e quatro populações de plantas, conforme estudo anterior. Utilizou-se o delineamento em blocos casualizados, com três repetições, com mudas micropropagadas da cultivar Vitória. Avaliaram-se as características de crescimento da planta (número de folhas emitidas, comprimento e peso da folha "D" e diâmetro do caule), além do peso dos frutos com e sem coroa no final do cultivo. Não foi observada interação entre densidade de plantio, doses de N e dias após o plantio (DAP). O aumento da densidade de plantio reduziu o diâmetro do caule do abacaxizeiro, no entanto não interferiu no peso dos frutos, indicando a possibilidade de aumento da população de plantas para o incremento da produtividade. A utilização de ureia como fonte de N promoveu maior crescimento e peso dos frutos do abacaxizeiro. A utilização de doses de N na forma de ureia e esterco promoveu maior crescimento do abacaxizeiro e incremento linearmente no peso dos frutos, indicando a dose de 20 g planta-1 na forma de ureia, como recomendação de adubação nitrogenada para o cultivo do abacaxizeiro 'Vitória' irrigado.

Genomewide Selection to Introgress Semidwarf Maize Germplasm into U.S. Corn Belt Inbreds

ABSTRACTSemidwarf maize (Zea mays L.) could be grown in new areas of production or in alternative crop rotations. Our objectives were to determine (i) if genomewide selection is useful for the rapid improvement of an exotic × adapted cross, (ii) if genomewide selection is more effective than phenotypic backcrossing for a trait with major genes, and (iii) the extent to which the high grain yield of nondwarf maize can be combined with the reduced stature and adaptability to high plant population densities of semidwarf maize. We conducted four cycles of genomewide selection in two semidwarf × adapted crosses. Phenotypic backcrossing was also done until the BC4 with selection for short plants. The accuracy of genomewide predictions in Cycle 0 was 0.67 to 0.70 for plant height and 0.57 to 0.70 for grain yield. Genomewide selection from Cycle 1 until Cycle 5 either maintained or improved on the gains from phenotypic selection achieved in Cycle 1. Observed gains generally agreed with predicted gains. Cycle 5 did not always have the best mean performance. Unfavorable genetic correlations made it difficult to select for short plants with high grain yield. Linkage disequilibrium between markers declined as selection progressed. Compared with phenotypic backcrossing, genomewide selection led to better mean performance and a higher proportion of exotic germplasm introgressed. To our knowledge, this is the first empirical study on genomewide selection to improve an exotic × adapted cross.