Seeding Rate Interaction Research Articles

396 Effects of allocation timing on cattle performance and forage utilization when swath grazing a sorghum-sudangrass hybrid in eastern Nebraska

Abstract Swath, or windrow, grazing is the process of cutting hay, leaving it in windrows, and allowing cattle to graze these windrows in the winter. This grazing system reduces winter feeding costs by mitigating the need to bale and transport hay, while having the potential for increased utilization compared with grazing the forage standing. This study aimed to determine the effect of varying allocation timing on cattle performance and forage utilization. A sorghum-sudangrass hybrid (Sorghum× drummondii) was planted in June 2023, cut in early November, and grazed from mid-November 2023 to mid-January 2024. A 16-ha field was divided based on seeding rate with one-half seeded at the recommended rate of 39.2 kg/ha (REC) and one-half with a double rate of 78.4 kg/ha (DOU). The field was subdivided into a total of 8 paddocks (4 per seeding rate) with either 10 (n = 4) or 11 (n = 4) windrows. Forage was cut and windrows were gathered from a 4.57 m width in the field. Prior to grazing, a 0.30 m length of three swaths in each paddock was sampled to determine initial forage mass. A total of 60 steers [initial body weight (BW) = 240 ± 8.3 kg] were stratified by BW and assigned to one of 8 paddocks (n = 7 or 8 calves) to result in equal BW per swathed area. Allocations were offered in full once-per week (1X) or, one-half of the total forage was allocated twice weekly (2X). Post-graze samples were collected to estimate utilization and allocation amount was adjusted as needed based on visual appraisal of post grazing biomass. Cattle were pulled from the field due to snow cover after a 64-d grazing period. The area grazed was used to calculate the animal unit months/ha (AUM) achieved for each paddock. Pre-grazing forage mass did not differ between allocation timing (P = 0.89) or among seeding rates (P = 0.10; REC = 6,720 ± 545 kg/ha, DOU = 8,534.0 ± 545 kg/ha). There was an allocation timing by seeding rate interaction (P < 0.01) for forage offered with 1X (10.62 kgּ steer-1ּ d-1) being offered more (P < 0.01) than 2X (8.43 kg/steer/d) within REC, but no difference (P = 0.31) in forage offered due to allocation within DOU (8.31 kgּ steer-1ּ d-1). However, post grazing biomass (P = 0.35) and utilization (59 ± 8%) were not affected by allocation timing (P = 0.48). Average daily gain (ADG) also did not differ (P = 0.93) due to allocation timing (0.20 ± 0.07 kg). Most notably, there was a significant allocation effect (P = 0.05) on AUM/ha with 1X (14.51 ± 1.00) being lesser than 2X (16.82 ± 1.00). However, there was no significant difference (P = 0.30) in forage disappearance (291 ± 61 kg/AUM) due to allocation timing. This indicates that more frequent allocations can lead to increased carrying capacity. Increasing the frequency of allocation is a simple management practice producers can implement when swath grazing sorghum-sudangrass to increase carrying capacity.

Brassica carinata physiological response to land preparation method and seeding rate

ABSTRACT Best management practices that optimize agronomic performance and make Brassica carinata production compatible with existing cropping systems are crucial for the establishment of a carinata supply chain in the southeastern United States. To this end, research was carried out to quantify land preparation method (conventional, no-till, broadcast-disc, and ripper-roller) and seeding rate effects on (1.12, 5.60, 10.09, and 14.57 kg seed ha−1) on B. carinata physiology, yield, and seed chemical composition. Data were collected on days to 50% flowering; canopy cover; gaseous exchange parameters (leaf net photosynthesis, stomatal conductance, transpiration, intercellular CO2, and water use efficiency); leaf area index; root weight; shoot weight; aboveground biomass; yield; and seed chemical composition. Leaf net photosynthesis was affected by land preparation treatment, being greater under the ripper-roller treatment, particularly during bolting. On the other hand, a decrease in photosynthesis, stomatal conductance, and water use efficiency was observed as seeding rate increased, especially during bolting. Carinata seed under the ripper-roller land preparation had the greatest oil content but lowest glucosinolates and protein contents. Yield did not respond to land preparation. Yield was minimized (732 kg seed ha−1) at the 1.12 kg ha−1 seeding rate and maximized (1087 kg seed ha−1) at the 5.6 kg ha−1 seeding rate. No land preparation by seeding rate interaction was observed for gas exchange parameters and LAI during any of the growth stages, nor was any interaction observed for yield. Carinata’s physiological response to seeding rate did not depend on land preparation method employed.

Maximizing soybean yield by understanding planting date, maturity group, and seeding rate interactions in North Carolina

AbstractGrowers across theU.S. Southeast use a diversity of soybean [Glycine max (L.) Merr.] planting dates, maturity groups, and seeding rates for soybean production depending on their rotational complexity. Studies were conducted across seven North Carolina environments in 2019 and 2020 to determine the effect of planting date (mid‐March through mid‐July), maturity group (MG 2–8), and seeding rate (185,329–432,434 seeds ha–1) on soybean emergence, stand, and yield. Across environments, soybean typically emerged more quickly with later planting dates; however, there were location‐specific variations in soybean emergence due to weather conditions around the time of planting. The longest and shortest emergence periods were 26 d for soybean planted in mid‐March and 4 d for soybean planted in June and July, respectively. In the higher yielding environments, yield was maximized with MG 3–4 cultivars planted at early April planting dates and yield declined as planting was delayed. In the low yield environments, yield was maximized with late April to mid‐May planting dates, typically with MG 5–7 cultivars. There was a penalty in both yield environments to planting past mid‐May and in the low yield environments for planting before mid‐April. Across environments, yields tended to be more similar among cultivars higher than MG 3 at planting dates in June and July. The effect of seeding rate on soybean yield was variable across planting dates, maturity groups, and yield environments. Future research is needed in North Carolina to validate the planting date and maturity group interactions on yield observed in this experiment to capture more variation in weather conditions.

Tillage system and seeding rate effects on the performance of Brassica carinata

AbstractBrassica carinata, a nonfood oilseed crop, is used to produce renewable fuels because of its high oil content and favorable fatty acid profile. Production in the southeastern United States is relatively new, and information on agronomic management practices to optimize growth and yield is limited. Since optimal seeding rate may depend on the land preparation method for this small‐seeded crop, a study was conducted to evaluate the effect of tillage system (conventional, no‐till, broadcast‐disc, and ripper‐roller) and seeding rate (1.12, 5.60, 10.09, and 14.57 kg seed ha−1) on the performance of B. carinata. A randomized complete block design with a strip‐plot restriction on randomization and four replications was implemented in Headland, AL, Jay, FL, and Quincy, FL, over five site‐years during the 2017–2018 and 2018–2019 growing seasons. Data were collected on soil residue cover; plant population; soil penetrometer resistance and moisture; biomass (including carbon and nitrogen); stalk diameter; yield and yield components; seed oil, protein, and glucosinolates concentration; and oil composition. Soil penetrometer resistance was significantly affected by tillage system, with the ripper‐roller consistently having the lowest penetration resistance values across all site‐years. Ripper‐roller tillage had the highest oil content and lowest protein and glucosinolate contents. Yield response to tillage system was variable. Among seeding rate treatments, yield was lowest at 1.12 kg seed ha−1 and similar among 5.60, 10.09, and 14.57 kg seed ha−1 at all site‐years. There was no tillage by seeding rate interaction for yield. Results indicate that among seeding rate treatments used, 5.6 kg seed ha−1 rate was optimal at all site‐years regardless of land preparation method and is thus the recommended seeding rate for commercial carinata production in the Southeastern United States.

The influence of seeding rate and micronutrients foliar application on grain yield and quality traits and micronutrients of durum wheat

A field experiment was conducted to evaluate the effect of seeding rate and foliar application of micronutrients and their synergistic effects on grain yield and quality traits of durum wheat. A split-split plot design was used with varieties assigned to the main plot, micronutrient to the sub plots and seeding rates to the sub-sub plots. Varieties were sown at seeding rate of 100, 125, 150 and 175 kg ha−1 and treated with ZnSO4 and FeSO4, applied foliarly at 25 kg ha−1 during anthesis stage. Significant differences among seeding rates, varieties and micronutrients and some of their interactions were observed. Higher seeding rate increased grain and biomass yields by 23.5% and 21.5%, respectively. Increasing seed rate from 100 to 175 kg ha−1 has reduced protein, gluten and Zeleny contents by 8.7%, 10.8% and 9.1%, respectively. FeSO4 × seeding rate interaction improved quality traits better than ZnSO4 interacted with seeding rate. Application of ZnSO4 and FeSO4 has increased Zn and Fe concentrations in the harvested grain. Agronomic biofortification could be an approach to overcome health problem related to Zn and Fe deficiency if used in combination with crop varieties with known genetic response to applied micro fertilizers.

Genotype by Seeding Rate Interaction in Wheat

Genotype by Seeding Rate Interaction in Wheat

Corn Response to Row Spacing and Seeding Rate Varies by Hybrid and Environment in Kentucky

There has been recent interest in growing corn in narrow rows (<30 inches wide) and at dense plant populations to increase grain yields. The purpose of this study was to evaluate three corn hybrids adapted to the midsouthern United States at multiple row spacings and seeding rates. Studies were established at Lexington and Hodgenville, KY during the 2011 and 2012 growing season. The corn hybrids were planted in 15‐inch rows, twin 8‐inch rows on 30‐inch centers, and 30‐inch rows at seeding rates of 30,000; 35,000; 40,000; and 45,000 seeds/acre. Plant stands, stalk diameter, intercepted photosynthetically active radiation, and grain yield were evaluated for all hybrid × row spacing × seeding rate combinations. Stalk diameter decreased with increasing seeding rates, but no lodging was observed. At Hodgenville in 2011, corn planted in twin rows yielded 6.7% more than corn in 30‐inch rows, but row spacing did not affect yield in the other site‐years. Under favorable growing conditions at Lexington in 2011, grain yield increased by 1.5 bu/acre per 1000 seed increase in seeding rate; however, under hot and dry conditions in 2012, grain yield decreased 0.87 bu/acre for every 1000 seed increase in seeding rate. At Hodgenville in 2012, a hybrid × seeding rate interaction was observed in which one hybrid responded positively, one responded negatively, and one was unresponsive to seeding rate. Corn producers considering decreasing row widths or increasing plant population density should ensure that they choose hybrids appropriate for their management systems and environmental conditions.

High perennial ryegrass seeding rates reduce plant size and survival during the first year after sowing: does this have implications for pasture sward persistence?

AbstractFailure of perennial ryegrass swards to persist is a key issue on dairy farms in many areas of the world. This study describes an experiment conducted to test the hypothesis that high ryegrass seeding rates (>18 kg seed ha−1) reduce plant size and physical survival during the first year after sowing, with negative implications for population persistence. Four cultivars representing four functional types of perennial ryegrass were sown at five seeding rates (equivalent to 6, 12, 18, 24 and 30 kg seed ha−1) with white clover in three dairying regions of New Zealand. Plant establishment rates, size and survival were measured for the first 13 months after sowing. Herbage accumulation, botanical composition and perennial ryegrass tiller density were also monitored. Increasing seeding rate reduced plant survival in the seven weeks after sowing, reflecting likely differences in germination and very early mortality of small seedlings. Thereafter, plant survival was relatively high and consistent across seeding rates at two sites but was consistently greater in the 6 kg ha−1 treatment compared with the 24 and 30 kg ha−1 treatments at one site. Higher seeding rates also increased ryegrass tiller density and the contribution of ryegrass towards total herbage biomass but reduced the contribution of white clover. Very few cultivar × seeding rate interactions were detected for any of the measured variables. Many of the seeding rate effects dissipated by the end of the first year after sowing, indicating that high seeding rates did not predispose swards to poor persistence in the longer term, irrespective of ryegrass functional type.

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.

The Effects of Seeding Rate on Older Stands of Glyphosate‐Tolerant Alfalfa

Increased seed cost of glyphosate tolerant (GT) compared to non‐GT alfalfa (Medicago sativa L.) raises questions about reducing seeding rates. The objective of this study was to determine if alfalfa stand density, yield, and forage quality are compromised in the later years of the stand when reduced seeding rates, in combination with glyphosate application, were used during establishment. At seven locations in the United States, GT alfalfa was seeded into conventionally tilled seedbeds at 6.7, 11.2, 15.7, and 20.2 kg ha−1 pure live seed (PLS) in the spring of 2006. Stand density, yield, and forage quality were determined for each seeding rate under three herbicide treatments: (i) glyphosate [N‐(phosphonomethyl)glycine], (ii) non‐glyphosate herbicide, and (iii) no herbicide. For the third through fifth years of the alfalfa stand, there was no herbicide treatment × seeding rate interaction. Higher seeding rates resulted in higher plant densities. The 11.2 and 15.7 kg ha−1 seeding rates had greater alfalfa and total forage (alfalfa + weeds) yields than the 6.7 kg ha−1 seeding rate. Herbicide treatments had no effect on alfalfa plant density but produced cumulative (over the duration of the study) alfalfa yield in the following order: glyphosate > non‐glyphosate > no herbicide. Cumulative total forage yield was less when no herbicide was used compared to using a herbicide. While forage fiber content was generally unaffected by seeding rate or herbicide treatments, using glyphosate to control weeds during alfalfa establishment increased forage crude protein content of older alfalfa stands compared to no weed control.

Lack of Hybrid, Seeding, and Nitrogen Rate Interactions for Corn Growth and Yield

Corn (Zea mays L.) seeding rates have increased because new hybrids purportedly optimize yield at high seeding and N rates. Two hybrids were evaluated in New York at four seeding and two sidedress N rates to determine if recommended rates (74,100 kernels ha−1 and 111 kg N ha−1) still optimize yield. Precipitation from June through August varied (389 mm in 2010 and 198 mm in 2011), so year × hybrid and year × seeding rate interactions existed for yield and yield components, but no two– or three‐way interactions existed among hybrid and N and seeding rates. Quadratic regression analysis predicted maximum yield at 88,000 kernels ha−1 in 2010, although yields varied by only 2% between 74,100 (18.5 Mg ha−1) and 98,800 kernels ha−1 (18.9 Mg ha−1). Seeding rate did not affect yield in 2011. As seeding rates increased from 61,875 to 98,800 kernels ha−1, kernel number per plant had negative linear decreases in 2010 (818 to 694) and 2011 (567 to 383). Kernel weight had a negative quadratic response to seeding rates in 2010 but a linear response in 2011 (338 to 317 and 312 to 332 mg, respectively, from 74,100 to 98,800 kernels ha−1). A year × N rate interaction existed for kernel weight (320 and 338 mg in 2010 and 318 mg in 2011 at 111 and 167 kg N ha−1, respectively) but not for yield (18.2 and 18.4 Mg ha−1 in 2010 and 11.1 and 11.3 Mg ha−1 in 2011, respectively). Overall, recommended seeding and sidedress N rates achieved close to optimum yield in this study.

Location, Variety, and Seeding Rate Interactions with Soybean Seed‐Applied Insecticide/Fungicides

Cool conditions after soybean [Glycine max (L.) Merr.] planting may increase soil pest incidence and reduce emergence. Field‐scale studies were conducted in 2009 and 2010 at three locations in New York on two varieties at four seeding rates (272,000, 346,000, 420,000, and 490,000 seeds ha−1) with and without seed‐applied insecticide/fungicides to determine if treated seed enhances plant establishment, allowing for lower seeding rates for maximum yield and partial return. Plant density and yield had location × variety × seed treatment interactions. A treated vs. untreated Asgrow variety had 16 to 22% plant density increases and 4% yield increases at two locations, whereas a Pioneer variety had a 16% density increase at one location but no yield increases. At a third location, the treated vs. untreated Pioneer variety had 19 and 4% increases, respectively, whereas the Asgrow variety had no increases. Yield, which had no seeding rate × seed treatment interaction, had quadratic responses to seeding rate and early plant densities (maximum yield at 478,300 seeds and 295,300 plants ha−1, respectively). Partial return, which had a seeding rate × seed treatment interaction, had quadratic responses to seeding rate with maximum values at 398,800 and 341,800 seeds ha−1 for untreated and treated seed, respectively. Maximum partial returns at these seeding rates ($1241–1245 ha−1, respectively) were similar because seed treatment cost offset lower seed cost. Maximum partial return occurred at early plant densities of 248,400 plants ha−1, but the variety × location × seed treatment interaction complicates selecting seeding rates for this plant density.

Lack of Hybrid by Seeding Rate Interactions for Corn Growth, Silage Yield, and Quality

Transgenic Bt (Bacillus thuringiensis) corn (Zea mays L.) hybrids may require higher but brown midrib (BMR) and leafy hybrids may require lower seeding rates than currently recommended for silage in the northeastern United States. We planted dual‐purpose (three Bt and one non‐Bt) two silage‐specific and two BMR hybrids to evaluate growth, dry matter (DM) yield, and quality responses to four seeding rates (61,750–98,800 kernels ha−1). Hybrid × seeding rate interactions were not observed. At silking (R1), BMR hybrids averaged 6% lower leaf area index (LAI, 4.58) compared with dual‐purpose hybrids and 7% lower biomass (1050 g m−2) compared with two dual‐purpose hybrids. Crop growth rates were similar from the 14th leaf (V14) to R1 stage between BMR and dual‐purpose hybrids (34.3–35.8 g m−2 d−1) so less BMR vegetative growth was associated with 10% lower LAI (3.46) and biomass (480 g m−2) at V14. Biomass and LAI had linear responses to seeding rates. The BMR compared with two dual‐purpose hybrids averaged 8% lower DM yield (20.7 Mg ha−1) but similar predicted milk yield (37.6 Mg ha−1) because of 8% higher milk Mg−1 values (1823 kg Mg−1). Silage‐specific compared with two dual‐purpose hybrids averaged about 7.5% lower DM and milk yields because of similar milk Mg−1 (1685 kg Mg−1). Milk and DM yields showed quadratic, and milk Mg−1 showed negative linear responses to seeding rates. Results indicate that Bt, BMR, and silage‐specific hybrids should be seeded at about 89,000 kernels ha−1 for silage in New York.

The Effects of Glyphosate‐Tolerant Technology on Reduced Alfalfa Seeding Rates

Higher costs associated with glyphosate tolerant (GT) compared to nonGT alfalfa (Medicago sativa L.) seed stimulates questions about reduced seeding rates in combination with the GT technology. Our objective was to determine if glyphosate herbicide in combination with GT alfalfa could improve the persistence, productivity, or forage quality when seeding alfalfa at a reduced rate. Glyphosate‐tolerant alfalfa was seeded at seven locations into conventionally tilled seedbeds at rates of 6.7, 11.2, 15.7, and 20.2 kg ha−1 pure live seed (PLS) in the spring of 2006. Stand density, botanical composition, yield, and forage quality were determined for each seeding rate under three herbicide treatments: (i) glyphosate [N‐(phosphonomethyl)glycine], (ii) a nonglyphosate herbicide, and (iii) no herbicide. Level of weed infestation was different among locations, but there were no weed infestation × seeding rate or herbicide × seeding rate interaction. Lower seeding rates had lower plant mortality than higher seeding rates. Seeding rate had no affect on forage quality or weed content at any harvest. At only the first harvest in the seeding year did the 6.7 kg ha−1 seeding rate produce less alfalfa forage (about 250 kg ha−1) than other seeding rates. In both the seeding year and year after seeding, using herbicides resulted in less weed and greater alfalfa yield than when no herbicide was used. Regardless of weed control treatment, seeding rates of GT alfalfa greater than 6.7 kg ha−1 did not improve weed control, alfalfa yield, total herbage (alfalfa + weeds) yield, or forage quality.

Management of wild oat (Avena fatua L.) in tame oat (Avena sativa L.) with early seeding dates and high seeding rates

Traditionally, farmers have delayed seeding to manage wild oat (Avena fatua L.) in tame oat (Avena sativa L.) crops, but this practice can adversely affect grain yield and quality. The objectives of this study were: (1) to evaluate the effectiveness of using high seeding rates with early-seeded oat to maintain grain yield and quality, and (2) to determine an optimum seeding rate to manage wild oat and maximize grain yield and quality. The factors of interest were wild oat density (low and high density), seeding date (early May, mid May, early June and mid June), and tame oat seeding rate (150, 250, 350 and 450 viable seeds m-2). The study was conducted at Indian Head and Saskatoon, SK, in 2002, 2003 and 2004, at Winnipeg, MB, in 2002, and at Morden, MB, in 2003 and 2004. Wild oat biomass, wild oat panicle density and wild oat seed in the harvested sample decreased as seeding rate increased, while tame oat biomass and grain yield increased. Wild oat density ranged between 0 and 100 plants m-2 with averages of 10 plants m-2 in the low density treatment and 27 plants m-2 in the high density treatment. At low seeding rates, grain yield decreased with increasing wild oat density. The difference in grain yield between the two wild oat densities decreased as the seeding rate increased. There was a curvilinear decrease in grain yield as seeding was delayed. A seeding date × seeding rate interaction was noted for test weight, plump seed, thin seed and groat yield. Seed quality improved as seeding rate increased for only the mid-June seeding date. Even though the mid-June test weight increased as the seeding rate increased it was always lower than the early May test weight at any seeding rate. The results from this study established that in the presence of wild oats, early seeding of tame oat is possible providing high seeding rates, 350 plants m-2 are used.Key words: Wild oat competition, wild oat density, wild oat biomass, grain yield, grain quality

Grain yield, and dry matter and nitrogen accumulation and remobilization in durum wheat as affected by variety and seeding rate

The influence of crop density on the remobilization of dry matter and nitrogen from vegetative plant parts to the developing grain, was investigated in the durum wheat ( Triticum durum Desf.) varieties Creso, Simeto and Svevo cultivated in the field at three seeding rates, 200, 250 and 400 seeds m −2. Variety × seeding rate interaction was unsignificant for all recorded characters. Grain yield declined in the order Svevo > Simeto > Creso. Yield differences mainly depended on the different number of kernels per unit land and, secondly, on mean kernel weight. Spike components differed among varieties: Svevo and Simeto showed more kernels per spikelet and Creso more spikelets per spike. Grain yield was highest with 400 seeds m −2 primarily due to the higher number of spikes per unit area, and secondly, to the higher mean kernel weight. Post-heading dry matter accumulation was highest in Svevo and lowest in Creso, but varieties showed a reverse order for dry matter remobilization and contribution of dry matter remobilization to grain yield. The increase of seeding rate increased both the post-heading dry matter accumulation and the dry matter remobilization from vegetative plant parts to grain. Nitrogen uptake of the whole crop and N content of grain was higher in Simeto and Svevo than in Creso. The N concentration of grain did not vary among varieties, but Svevo showed a markedly lower N concentration and N content of culms at maturity, which may be consequence of the high N remobilization efficiency performed by this variety. The N uptake by the crop was highest with 400 seeds m −2, but the N concentration of culms, leaves and even grain was slightly lower than with the lower seed rates. The post-heading N accumulation was by far higher in Simeto and Svevo than in Creso, whereas remobilization was highest in Svevo and lowest in Simeto. The percentage contribution of N remobilization to grain N was by far higher in Creso than in the other two varieties. Post-heading N accumulation and N remobilization were highest with the highest plant density, but the contribution of N remobilization to N grain content did not differ between seeding rates.

Optimizing Seeding Rates for Winter Cereal Grains and Frost‐Seeded Red Clover Intercrops

Growing winter cereal grain/forage legume intercrops can provide multiple benefits to cropping systems in the North Central USA. Intercropping red clover (Trifolium pratense L.) with winter cereal grains can provide forage and a green manure crop. Seeding rate recommendations for sole crops may not optimize intercrop system productivity if interactions exist. This study was conducted during the 2002–2003 and 2003–2004 growing seasons to determine optimum cereal grain and red clover forage seeding rates for maximum returns using partial budget analyses. In March, red clover was frost‐seeded at 0, 300, 600, 900, 1200, and 1500 seeds m−2 into winter wheat (Triticum aestivum L.) and triticale (X Triticosecale Wittmack) seeded at 100, 200, 300, and 400 seeds m−2 the previous October. Triticale and wheat maximized returns at seeding rates of 300 and 400 seeds m−2. No cereal grain by red clover seeding rate interactions were detected for red clover dry matter production (DM). Red clover plant densities after cereal grain harvest were 10 to 22% of the original seeding rates. Red clover DM production and return was maximized at 3.49 Mg ha−1 with 900 seeds m−2 in 2003 and 6.67 Mg ha−1 with 1200 seeds m−2 in 2004. Winter cereal/red clover intercrops in the North Central USA can maximize return using a cereal grain seeding rate between 300 and 400 seeds m−2 and red clover seeding rates between 900 and 1200 seeds m−2

Seeding Rates for Stale Seedbed Rice Production in the Midsouthern United States

The establishment of an adequate and uniform rice (Oryza sativa L.) stand is critical to achieve high grain yields. The literature is extensive for older cultivars planted in conventional tillage and/or water‐seeded systems; however, there are no published data for current cultivars grown in stale seedbed systems. Six of the cultivars most commonly grown in the Midsouth rice production area of the USA were drill seeded at densities of 108, 215, 323, 430, and 538 seeds m−2 into a stale seedbed at Crowley, LA, from 2002 to 2004, and in Clarksdale, MS, in 2003 and 2004. Established plant densities responded linearly to seeding rate for all cultivars except Cocodrie, which responded quadratically. Rough rice yields were not affected by seeding rate for Cheniere, but followed a quadratic relationship for the cultivars CL161, Cocodrie, and Priscilla. A location × seeding rate interaction was detected for yield of Wells. Seeding rate did not affect rough rice yields for Wells in Mississippi, while in Louisiana, yields responded quadratically. Francis rough rice yields increased linearly with increased seeding rates. Optimal rough rice grain yields can be achieved in Mississippi and Louisiana with a seeding rate of 323 seeds m−2 for cultivars that are currently grown across the Midsouth rice‐producing area in the USA. Furthermore, depending on the cultivar, when plant densities are uniform and range from 50 to 70 plants m−2, the resulting rice grain yields may offset the cost of terminating the stand and replanting.

Field pea seeding management

The impact of seed placement and seeding rate on crop yield is not clearly understood for field pea (Pisum sativum L.). A field experiment was conducted at Melfort, SK, and Lacombe, AB, in 1998 and 1999, to evaluate the effect of three seed placements (distinct row: 23 cm and 30 cm with a hoe opener; and spread band: a 20-cm spread using a 28-cm sweep on a 23-cm row spacing) and three seeding rates (50, 100, and, 150 seeds m-2) on pea seedling density, seed yield and seed weight of a leafy prostrate and semi-leafless upright cultivar. A follow-up experiment was conducted at seven sites across Saskatchewan in 2001 to further examine the influence of a wider range of seeding rates (20, 30, 40, 50, 60, 70, 80, 90, 100, and 120 target plants m-2). Pea productivity for both cultivars was not affected by the different seed placements, despite a 4 mg greater seed weight for distinct row seed placements compared with spread band placement across all 1998–1999 sites. Moreover, the absence of a seed placement by seeding rate interaction indicated that greater spacing between plants was not associated with improved pea yield when seeding rate was increased, regardless of the cultivar. Yield component compensation occurred where increased plant density from higher seeding rates reduced seed weight. In the 2001 study, seed yield benefits were small at seeding rates greater than 50 target plants m-2. There was a tendency for lower yields with seeding rates less than 50, especially at sites with higher yield potential. Yields of field peas grown under relatively weed-free conditions should be optimized with a seeding rate of 50 to 75 seeds m-2. Key words: Pea (Pisum sativum L.), plant arrangement, row spacing, opener type, seeding rate

Wild Oat (Avena fatua) Interference in Barley (Hordeum vulgare) is Influenced by Barley Variety and Seeding Rate1

Abstract: Field experiments were conducted at Vegreville and Lacombe, AB, to determine the influence of barley (Hordeum vulgare) variety and seeding rate on interference of wild oat (Avena fatua) with barley. Barley variety and seeding rate affected barley density, height at maturity, and seed yield, as well as wild oat shoot dry weight and seed yield in most experiments, but there was no variety by seeding rate interaction. As expected, the semidwarf varieties Falcon and CDC Earl were the shortest. Barley seedling emergence and subsequent plant densities varied among varieties, locations, and years. The hull-less varieties Falcon and CDC Dawn had the poorest emergence in most cases, whereas AC Lacombe and Seebe had the highest emergence. Wild oat shoot dry matter and seed production was highest in the Falcon, CDC Dawn, and CDC Earl plots, suggesting that these were the least competitive with wild oat. Barley yield loss from wild oat interference also tended to be highest in these varieties. Poor emergenc...