Seasonal Dry Matter Research Articles

THE YIELD STABILITY AND QUALITY OF LEGUMES DURING TWO CONSECUTIVE, EXTREMELY DRY YEARS

Abstract This study highlights the effect of drought and ambient temperature on performance and herbage quality of legume monocultures and grass-legume mixtures. In a field experiment, the total dry matter yield, seasonal pattern of dry matter yield distribution, content of crude protein and crude fibre of monocultures of red clover and alfalfa and grass-legume mixtures were investigated during two consecutive dry years (2011-2012). Alfalfa cultivars Kamila and Tereza grown as monocultures or as mixtures with Festulolium braunii (cultivar Achilles) outperformed the red clover cultivars Fresko and Veles and provided a well-balanced total and seasonal dry matter yield during both years. Across all experimental years, crude protein content was significantly higher at alfalfa monocultures and mixture when compared with clover monocultures (P < 0.05). However, considerable lower content of crude fibre at clover monocultures in comparison with alfalfa ones was found. Responses of nutritive parameters of both legume species to weather variables were different. Crude protein content in red clover was independent of rainfall and temperature. In contrast, the crude fibre content correlated with temperature whereby the alfalfa monocultures showed stronger correlations (P < 0.05) than red clover monocultures.

Early season dry matter production of three hybrid ryegrass (Lolium boucheanum) and two perennial ryegrass (Lolium perenne) cultivars

Hybrid ryegrass (HRG) is purported to have high overwinter growth characteristics and may have a role in Irish grassland systems. In a 3-year small-plot study at Fermoy, Cork, Ireland, the dry matter (DM) production and herbage quality of HRG cultivars in early spring were compared with diploid and tetraploid perennial ryegrass (PRG) cultivars. Treatments comprised ryegrass cultivars × defoliation managements × defoliation heights in a 5 × 3 × 2 factorial arrangement. The cultivars were Navan (tetraploid PRG), Foxtrot (diploid PRG), Foyle (tetraploid HRG), Brutus (diploid HRG) and Belleek (tetraploid HRG). Defoliation dates were: (A) 2 February and 20 April; (B) 2 February, 3 March and 20 April; and (C): 2 February, 23 March and 20 April. Defoliation heights were 4 and 7 cm, applied across each management. The HRG cultivars yielded similarly to cv. Navan on 2 February. Cumulative spring DM production was higher in cvs. Brutus and Belleek than all other cultivars. During this period, the managements A and B had similar DM yields (2765 kg DM ha−1) but were greater than management C. Defoliating swards to 4 cm height increased DM yield compared with 7 cm height. Organic matter digestibility of grass at the silage-harvest growth stage was greater for PRG cultivars. The study indicates that early spring growth of the three HRG cultivars evaluated here was not sufficiently greater than the tetraploid PRG cv. Navan to compensate for their poorer midseason sward quality.

Growth and physiologic response of rapeseed (Brassica napus L.) to deficit irrigation, water salinity and planting method

Salinity and water stress reduces the ability of plant to take up water and decrease growth rate, photosynthesis rate (An) and stomatal conductance (gs) of plants. In this study, effects of deficit irrigation with different salinity levels and planting method (in-furrow and on-ridge) as strategies for coping with water and salinity stress on physiologic properties of rapeseed was investigated in a two years experiment. Irrigation treatments consisted of full irrigation (FI) and 0.75FI and 0.50FI in first year and 0.65FI and 0.35FI in second year and salinity treatments of irrigation water were 0.6 (well water), 4.0, 7.0 m and 10.0 dS -1 in first year and 0.6, 4.0, 8.0 and 12.0 dSm -1 in second year. Planting in-furrow increased seasonal dry matter by 8.4 and 9.6%, respectively at first and second year (with frost occurrence in dormant period in second year) relative to on-ridge planting. In-furrow planting increased maximum leaf area index compared with on-ridge planting by 12.8% for second year. Deficit irrigation and salinity decreased dry matter, leaf area index and had no significant effect on crop growth rate (CGR) and relative growth rate (RGR). Decrease in applied water resulted in lower stomatal conductance (gs) and photosynthesis rate (An) and salinity had no significant effect on these traits. Ratio of photosynthesis rate to transpiration rate (leaf scale transpiration efficiency, An/T) decreased when leaf vapor pressure deficit (VPD) increased and in water and salinity stress conditions, transpiration efficiency of rapeseed decreased. A linear function between An/T and VPD with negative slope indicated that in higher VPD, An/T decreased, therefore in water stress condition or in arid and semi-arid region in comparison with humid region An/T of rapeseed decreased. There was no significant difference between the effects of water salinity levels (up to 12 dS m -1 ) and planting method on slopes of the

Estimating theoretical radiation‐use efficiency for kale crops

AbstractEstablishing the radiation‐use efficiency (RUE) of forage brassica crops will aid our understanding of their photosynthetic performance. The concept of RUE has been developed for cereals and legumes, but there is limited information for forage brassica crops. Three experiments defining the influence of different sowing dates on ‘Gruner’ kale (Brassica oleracea acephala L.) dry matter production were conducted at Hastings (Hawkes Bay) and Lincoln (Canterbury) in New Zealand between 2002 and 2009. These trials were also evaluated for radiation interception and RUE. Delayed sowing increased RUE in two out of three experiments across sites: from 1·93 g MJ−1 photosynthetically active radiation (PAR) for December‐sown crops to 2·72 g MJ−1 PAR (P < 0·001) for January‐sown crops at Hastings and from 1·50 for September‐sown crops to 2·00 g MJ−1 PAR (P < 0·001) for November‐sown crops at Lincoln. The different sowing dates and years of experimentation provided a range of mean temperatures (from 13 to 16°C) during the vegetative period. Across years and sowing dates, RUE was strongly correlated with mean temperature (R2 = 0·81) and sowing date (R2 = 0·64), but weakly correlated with season length (R2 = 0·11) and dry matter (R2 = 0·002). There was also a strong correlation (R2 = 0·83) between sowing date and mean temperature. The increase in RUE with delayed sowing was therefore mainly attributed to increased mean temperatures. Radiation‐use efficiency increased at about 0·41 g MJ−1 for each 1°C increase from 13 to 16°C.

Herbage production from five grazable forages

Maintaining an adequate feed supply throughout the year is an important consideration in dairy systems. Systems based on perennial ryegrass pastures are often limited by poor growth and feed quality when soil moisture is low and temperatures are high. Alternative forage species better adapted to these conditions may provide options for maintaining feed supply. Annual and seasonal dry matter (DM) production, and nutritive value of five grazable forages with and without irrigation were compared under cutting in the Waikato over two successive years. Perennial ryegrass produced the greatest annual DM yield in both years under both irrigation regimes, largely through superior cool season production and mild temperatures with above average rainfall during the experiment. Plantain tended to provide more DM than perennial ryegrass under irrigation in summer and autumn, a time when additional DM is important for maintaining milk production. With the exception of sudan grass, nutritive value of all forages exceeded values expected to limit milk production. Keywords: dry matter yield, nutritive value, chicory, plantain, perennial ryegrass, sudan grass, sulla

Switchgrass silage for methane production as affected by date of harvest

Bélanger, G., Savoie, P., Parent, G., Claessens, A., Bertrand, A., Tremblay, G. F., Massé, D., Gilbert, Y. and Babineau, D. 2012. Switchgrass silage for methane production as affected by date of harvest. Can. J. Plant Sci. 92: 1187–1197. Switchgrass (Panicum virgatum L.) is a warm-season grass recognized as a potential biomass crop for energy production in North America, but little information exists on the effect of harvest date on forage and silage characteristics of switchgrass grown in eastern Canada. Our objectives were to determine how harvest date affects several forage and silage characteristics of switchgrass and to relate these to specific methane yield from anaerobically digested switchgrass silage. Switchgrass, seeded in 2002 and 2006, was harvested and ensiled as a one-cut system on three dates in 2007: late July, early September, and early October. The regrowth from the late July harvest was also harvested in early October as a two-cut system. Silage quality parameters [pH, and concentrations of N, N-NH3, total amino acids (TAA), and volatile fatty acids (VFA)] indicated adequate fermentation of all silage samples. In a one-cut system, delaying harvest from late July to early September increased forage dry matter (DM) yield from 9.0 to 11.5 Mg ha−1, forage soluble carbohydrate (SC) concentration from 51 to 85 g kg−1 DM, and silage SC concentration from 13 to 25 g kg−1 DM; delaying harvest from late July to early October decreased forage in vitro true digestibility (IVTD) from 720 to 582 g kg−1 DM, forage in vitro digestibility of the neutral detergent fibre (dNDF) from 590 to 409 g kg−1 DM, and silage acetate concentration from 7.7 to 2.6 g kg−1 DM. The regrowth had higher IVTD and dNDF, lower acid detergent fibre concentration, and higher silage lactate and acetate concentrations than a single harvest taken in early September or early October. The two-cut system and the single harvest in early September produced the highest seasonal forage DM yields (11.5 and 11.9 Mg ha−1). High specific methane yield was (i) correlated with low forage fibre concentration and high DM digestibility and (ii) more correlated to silage concentrations of lactate and acetate than to silage SC concentration.

Pasture and sheep performance response to sod-seeding red clover (Trifolium pratense L.) or white clover (Trifolium repens L.) into naturalized pastures in eastern Canada

Sheep farmers need low-cost, low-input pasture improvement techniques to optimize production in extensive systems. This study investigated the sod-seeding of red clover (Trifolium pratense L.) and white clover (Trifolium repens L.) into naturalized pastures in Nova Scotia, over three years, at three sites. Although red clover has shown potential to out-perform white clover under sod-seeding, there are concerns surrounding red clover and sheep reproduction. Using a randomized incomplete block design, both forage and sheep productivity were compared among three treatments: renovated red clover, renovated white clover and non-renovated control pastures. Renovated red clover and white clover pastures had legume contents of 0.18g/g dry matter (DM) and 0.10g/g DM respectively, greater than non-renovated pastures at 0.03g/g legume DM (P<0.001). August available DM was greater in renovated pastures but there was no treatment effect on seasonal DM yields. Red clover pastures had greater legume plant density (P=0.023), with 61.4plants/m2, than non-renovated pastures, with 30.9plants/m2. Red clover pastures promoted weight gain in lambs, with average daily gains of 0.21kg/d over the grazing season, higher than control lambs (0.17kg/d; P<0.001) and white clover lambs (0.18kg/d). Red clover ewes gained 8.9kg during the fall, after their lambs were weaned, greater than in ewes on control (6.2kg; P=0.049) or white clover pastures (6.7kg). There was no impact of renovation upon ewe fertility. Pasture renovation, particularly with red clover, improved pasture and sheep performance.

Effects of Abiotic Stress on Respiratory Carbon Loss of Two Maize (Zea mays L.) Inbred Lines and Their Hybrid During Silking and Grain‐Filling

ABSTRACTHigh‐yielding commercial maize (Zea mays L.) hybrids have higher seasonal dry matter accumulation (DMA) than their inbred parents, with the difference often being greater under conditions of abiotic stress. The greater DMA of high‐yielding maize genotypes has been attributed in part to maintenance of higher leaf photosynthetic capacity during the grain‐filling period, but it is possible that lower respiratory C loss also contributes to higher DMA. We compared the root and shoot dark respiration rates of a hybrid to those of its two parental inbred lines under resource‐replete conditions, and also under conditions of shade stress, water stress, and N stress. Stress treatments applied over a 3‐wk period around silking did not affect root or shoot respiration rates per unit dry weight (DW). By contrast, all three stress treatments reduced respiration per unit DW when the stresses were applied over 3 wk during the grain‐filling period. By 5 wk after silking, respiration per unit DW was significantly lower in the hybrid than in either of the inbred lines, but this may have been due to greater dilution of the respiration signal by the accumulation of structural biomass and/or storage tissues in the hybrid, rather than a lower respiration rate per se. We did not find strong evidence that the hybrid benefited from fundamentally lower respiratory requirements than its inbred parents, or that the hybrid and its parental inbreds differed in their respiratory responses to abiotic stress.

Economic values for evaluating pasture plant traits

Economic values (EVs) are an estimate of the change in farm system profit per unit of change in a defined plant trait. Cultivars within species such as perennial ryegrass differ in the major production traits of dry matter yield, nutritive value and persistence, but the impact of those differences on farm financial performance is seldom calculated and reported. This paper explains what EVs are, describes how they can be calculated, and discusses some of the associated methodological issues. EVs have been derived for seasonal dry matter yield in New Zealand dairy systems. Extra feed produced in late spring has consistently low economic value, while extra feed produced in early spring has consistently high value. There have been no systematic investigations into the EVs of nutritive value and persistence in New Zealand pastures; this is a clear opportunity for future research. The lack of data on cultivar differences in these traits will restrict the application of EVs to pasture cultivar evaluation. This gap is now being addressed by new industry initiatives. Keywords: pasture cultivars, evaluation, traits, economic values, performance values

Evaluating perennial ryegrass cultivars: improving testing

The agronomic performance of a range of perennial ryegrass cultivar-endophyte combinations was compared in 16 trials conducted at sites throughout New Zealand. Each trial was run for 3 years according to seed industry evaluation protocols, measuring variables including: dry matter (DM) yield (total annual and seasonal DM yield), ryegrass ground cover at the end of 3 years, susceptibility to plant pulling, and rust incidence. The change in DM yield over the 3-year term of each trial was also analysed. There were significant differences among cultivars in total annual DM yield, and in seasonal DM yield for each of the five periods of the year among which yield was split (winter, early spring, late spring, summer, and autumn). Mean annual yield declined between Year 1 and Year 3 in all regions except Taranaki, by between 0.8 t DM/ha (Canterbury) and 5.3 t DM/ha (Waikato). There were significant region, year, region × year, and cultivar × year interactions in yield change. Significant differences in ground cover score for perennial ryegrass at the end of 3 years were recorded among cultivars. However, these differences did not mirror on-farm observations of ryegrass persistence in the Waikato during the drought of 2007/08, suggesting that the standard trial protocols currently used do not adequately test persistence. It is recommended that industry cultivar testing needs to more accurately assess perennial ryegrass persistence, using new protocols including running trials on commercial farms, for more than 3 years, and using mixed swards. Genetic differences in persistence could be generated more quickly by choosing sites known to challenge perennial ryegrass growth and survival. Keywords: perennial ryegrass, cultivar evaluation, DM yield, persistence testing, plant pulling, rust

Crop yield and nitrogen concentration with controlled release urea and split applications of nitrogen as compared to non-coated urea applied at seeding

Controlled release urea (CRU) has been shown to improve nitrogen fertilizer use efficiency in a number of production systems. However, the effectiveness of CRU will be strongly affected by the environmental conditions of the region. Research trials were conducted at five locations across four major ecoregions spanning 1600km across the Northern Great Plains and Pacific Maritimes of North America from 2004 to 2006 to evaluate the effects of a single application of polymer-coated urea (CRU) or split applications of urea fertilizer as compared with non-coated urea for their effects on crop growth, crop N concentration, and crop N accumulation of wheat (Triticum aestivum L.), barley (Hordeum vulagre L.) canola (Brassica napus L.) and corn (Zea mays L.) across a wide range of environmental conditions. Urea applied as an in-soil band at the time of seeding was generally as or more effective than similarly placed CRU, split application of urea or blended urea and CRU in the semi-arid Mixed Grassland, moist Aspen Parkland or wet Boreal Transition ecoregions in increasing early season dry matter yield and seed or grain yield of canola, wheat or barley. Similarly, broadcast urea was as or more effective than broadcast CRU, split applications or blended applications in increasing corn dry matter yield under the wet conditions in the Lower Mainland ecoregion. There were some situations where use of split applications or use of the CRU in a blend with the non-coated urea resulted in increases in grain yield as compared to the non-coated urea, primarily under moist conditions in the Boreal Transition or Aspen Parkland ecoregions. Some yield losses occurred from use of the CRU as compared with the non-coated urea and were attributed to delays in release of N from the granule that limited early season N availability and crop growth, especially in corn with a high N demand. Effects on grain N concentration and accumulation of N in the crop at harvest were mixed, with the CRU, blended applications of CRU and urea or split applications occasionally producing higher grain N concentration and N accumulation in the crop than the non-coated urea. Benefits of CRU on grain N concentration were more frequent than benefits on grain yield, but were not large or consistent. Response of crop growth and N uptake to N management was generally similar under CT and RT, with occasional differences occurring due to changes in yield potential or N deficit associated with the differences in tillage management. Therefore, under growing conditions across a wide range of ecoregions in the Northern Great Plains and the Pacific Maritimes, the use of CRU or split applications do not appear to provide a consistent improvement in crop yield, N concentration in the grain, total N accumulation at harvest, or nitrogen use efficiency as compared to standard regional timing and placement of non-coated urea.

Seedling Establishment and Forage Accumulation of ‘Ceres Tonic’ Plantain in Pure Stands and in Grass Mixtures

This study evaluates the balance of species 2 mo after sowing, its effects on seasonal and annual dry matter accumulation of Plantago lanceolata L. �Ceres Tonic� sown in pure stands, in binary mixtures with three grasses, and different initial growth rates: annual ryegrass (Lolium multiflorum Lam.), tall fescue (Festuca arundinacea Schreb.), and orchard grass (Dactylis glomerata L.). Plantain monocultures were sown at three densities (4, 8, and 12 kg seed ha-1), while halved densities were used in the mixtures. Each grass was sown at the density that is typical for the region (annual ryegrass = 30, tall fescue = 15, and orchard grass = 6 kg seed ha-1). The trial was carried out in Balcarce (37o45� S, 58o18� W; 130 m a.s.l.), Argentina in 1.4 × 5 m plots sown in April 2005 with a randomized complete block design, a factorial arrangement of pasture type and plantain sowing density, and seasons as a measurement repeated over time. Plant density 2 mo after sowing was not a good estimator of the balance between species for all pasture types at the end of the first year. Total forage accumulation throughout the experimental period was affected by pasture type (p = 0.08) and plantain sowing density (p < 0.05), but not by their interaction (p > 0.05). The plantain and annual ryegrass mixture accumulated 28% more biomass than the mean biomass of all the other pastures (7948 ± 647 vs. 6204 ± 502 kg DM ha-1) mainly because of its higher yield in fall and winter. Total precipitation during the year under study was 15% lower than the historic average so that higher accumulations could be expected in years with higher precipitation.

Effects of sawdust bedding dry matter on lying behavior of dairy cows: A dose-dependent response

The objective was to determine the effect of sawdust bedding dry matter on the lying behavior of Holstein cows. Dry matter (DM) was varied systematically over 5 treatment levels to test how cows respond to damp bedding. This experiment was repeated during summer and winter to test if the effects of damp bedding varied with season. The 5 bedding treatments averaged (±SD) 89.8±3.7, 74.2±6.4, 62.2±6.3, 43.9±4.0, and 34.7±3.8% DM. Over the course of the trial, minimum and maximum temperatures in the barn were 2.6±2.0 and 6.8±2.2°C in the winter and 13.3±2.5 and 22.6±4.1°C in the summer. In both seasons, 5 groups of 3 nonlactating cows were housed in free stalls bedded with sawdust. Following a 5-d acclimation period on dry bedding, groups were exposed to the 5 bedding treatments in a 5 × 5 Latin square. Each treatment lasted 4 d, followed by 1 d when the cows were provided with dry bedding. Stall usage was assessed by 24-h video scanned at 5-min intervals. Responses were analyzed within group (n=5) as the observational unit. Bedding DM affected lying time, averaging 10.4±0.4 h/d on the wettest treatment and increasing to 11.5±0.4 h/d on the driest bedding. Lying time varied with season, averaging 12.1±0.4 h/d across treatments during the winter and 9.9±0.6 h/d during the summer, but season and bedding DM did not interact. These results indicate that access to dry bedding is important for dairy cows.

Agronomic performance and water-soluble carbohydrate expression of selected ryegrasses at two locations in New Zealand

Agronomic trials at cool (Gore) and warm (Palmerston North) temperate sites in New Zealand tested ten United Kingdom-bred (six diploids, four tetraploids) and two New Zealand-bred diploid (‘Bronsyn’, ‘Impact’) perennial and long-term hybrid ryegrasses (Lolium perenne, L. boucheanum) over two trial periods. Dry matter (DM) yields and persistence were better at the cool site but differential expression among cultivars for water-soluble carbohydrates (WSC) and yields was small compared with the warm site. The tetraploid cultivars generally had the highest concentrations of WSC but also on occasions had higher levels of crown rust, moderate DM yields and poorer persistence compared with diploids. Two of the tetraploid cultivars will be of value for their high WSC and good agronomic performance at the cool site. Some of the diploid UK cultivars expressed higher WSC and had similar or higher annual DM yields than some of the NZ-bred cultivars, and had high levels of resistance to crown rust. Overall, differences among cultivars in expression of WSC were small. Some differences occurred for seasonal DM yields with some UK cultivars having lower winter yields.

PHOSPHORUS AND ZINC INTERACTIONS IN CHELATOR-BUFFERED SOLUTION GROWN RUSSET BURBANK POTATO

High phosphorus (P) application in potato production potentially leads to antagonistic interactions with cationic micronutrients. None of the nine combinations of phosphorus and zinc (Zn) provided in chelator-buffer solution for 17 days to potato supported the concept of a P-induced Zn deficiency with regard to early season dry matter yield, especially when solution P ranged from sufficient to excessive—conditions under which P-Zn interaction traditionally is observed. Increased solution P at low Zn levels resulted in a steep increase of P in new and old shoot growth and an accumulation of manganese (Mn) in potato roots—a combination that might indirectly impact Zn nutrition in potato. Although high P levels in potato did not directly reduce Zn content or cause Zn deficiency, excessive P accumulation may reduce the activity of Zn by interacting with other micronutrients such as Mn.

The effect of sward perennial ryegrass content and defoliation method on seasonal and total dry matter production

The effect of sward perennial ryegrass content and defoliation method on seasonal and total dry matter production

Light and Moisture Competition Effects on Biomass of Red Clover Underseeded To Winter Wheat

Red clover (Trifolium pratense L.) use as an underseeded cover crop in winter cereals has declined due to inability of growers to consistently establish uniform stands. The objective of this study was to assess the effect of light and soil moisture competition on underseeded red clover establishment and end of season dry matter production. Field trials were conducted at multiple locations in 2005 and 2006 in Ontario, Canada. Wheat (Triticum aestivum L.) N rate (67 and 135 kg N ha−1) and row thinning treatments (19‐cm rows, every third 19‐cm row removed at the 4–5 leaf stage) were used to alter light penetration and soil moisture competition. The high N rate and row thinning treatments consistently reduced light penetration, beginning as early as wheat stem elongation initiation, but had no effect on soil gravimetric moisture content. Soil moisture was primarily affected by location and year. Red clover dry weight in 2005, a relatively dry year, ranged from 688 to 1184 kg ha−1, and in 2006, a relatively wet year, ranged from 2336 to 2805 kg ha−1. Average final red clover stand count was 23 plants m−2 in 2005 and 55 plants m−2 in 2006. In 2005, plant mortality occurred before wheat anthesis. In both years, and at most locations, red clover final dry weight was positively correlated with light penetration, again beginning as early as initiation of wheat stem elongation. Final red clover dry weight in both years and red clover stand count in 2005 were correlated with soil gravimetric water content during wheat anthesis, but this was primarily due to location and year effects. Although both light penetration through the wheat canopy and soil moisture influence biomass production of underseeded red clover, soil moisture has the greater influence and is altered very little by wheat management.

Yields of Alfalfa Varieties with Different Fall‐Dormancy Levels in a Temperate Environment

Fall dormancy (FD) is an important indicator of winter hardiness in alfalfa (Medicago sativa L.), but the relationship between FD and the yield potential of alfalfa varieties with contrasting FD classes has not been determined in the temperate regions with mild winters. This study was conducted with 42 varieties of eight FD classes (2–9) over four consecutive years to determine the relationship of seasonal and annual total dry matter (DM) yields with FD classes. The results showed that all the eight FD varieties survived over the winter without any persistency problems during the four production years. The greatest average DM yield of 24.4 Mg ha−1 yr−1 was achieved with ‘Runner’ (FD2), while the smallest yields were found in ‘Defi’ (FD5). There were no differences in annual DM yields of varieties among FD classes 3 and 5 to 9. Time of cuts affected DM yields (P &lt; 0.01) with the first three cuts accounted for 80% of the total yields. Dry matter yields for some of the dormant, semidormant and nondormant varieties were also the greatest and notable yield differences (P &lt; 0.05) were found among the same FD varieties, whereas overall annual total DM yields were not correlated with FD classes. Our data suggest that FD class should not be used as the main criteria for alfalfa variety improvement and/or introduction of new varieties into temperate regions, and also highlight the importance of early season management to achieve great annual total herbage yields in the temperate regions, such as North Central China.

Preplant Herbicides Don't Increase Forage Production of Cereal Rye Interseeded into Bermudagrass

Interseeding cereal rye (Secale cereale L.) into a bermudagrass sod [Cynodon dactylon (L.) Pers.] can increase season‐long forage production and land use efficiency. However, previous research has shown that competition from the bermudagrass sod can significantly reduce autumn forage production from cereal rye. Our objective was to determine if the application of a preplant herbicide to a bermudagrass sod before interseeding cereal rye influenced seasonal or total annual forage dry matter (DM) yields in the southern temperate‐humid zone. In mid‐September, cereal rye was interseeded into bermudagrass after treating with (i) no herbicide, (ii) 1.37 kg a.i. ha−1 of paraquat dichloride (Gramoxone), or (iii) 0.56 kg a.i. ha−1 of clethodim (Select). The control treatment was bermudagrass sod that was neither treated with herbicide nor interseeded with cereal rye. Treating with Select reduced forage DM yield in the subsequent summer by as much as 35% compared with unseeded bermudagrass. Treating with Gramoxone did not improve forage DM yield in autumn. Forage DM yield was approximately 3300 to 4500 kg ha−1 greater in autumn and spring when cereal rye was interseeded into bermudagrass, but the net increase in forage DM yield for the cereal rye–bermudagrass system was only 1100 to 3300 kg ha−1 yr−1 greater than the unseeded control, which yielded 10,000 kg ha−1. Producers who stock growing or lactating animals in autumn or spring would benefit most from this practice because the cereal rye would be available for grazing at a time when many forage–livestock systems must use more expensive stored feedstuffs.

The effects of clipping height and frequency on net primary production ofAndropogon gerardii(C4grass) andBromus inermis(C3grass) in greenhouse experiments

AbstractThere are potential agronomic and environmental benefits from incorporating warm‐season (C4) grasses into temperate pasture systems, usually dominated by cool‐season (C3) grasses, but there is a lack of information on how frequency and height of defoliation affects C4grasses. Three greenhouse experiments were conducted under (i) spring, (ii) summer and (iii) spring + summer clipping regimes. In each experiment, the effects of clipping frequency (weekly and monthly) and clipping height (clipped to 5 and 10 cm) were determined on above‐ and below‐ground net primary production (ANPP and BNPP) and total and seasonal dry matter (DM) yield forAndropogon gerardiiVitman (big bluestem, C4grass) andBromus inermisLeyss (smooth brome, C3grass). Six replicates per treatment were used. In all experiments, ANPP and BNPP of smooth brome was greater than that of big bluestem although during late summer months big bluestem had higher DM yields of herbage than smooth brome. There were different effects of frequency and height of clipping for both species on two similar measurements: total annual DM yield and ANPP, indicating that the ability to generalize about the effects of defoliation from ecological and agronomic grassland standpoints is questionable. Clipping effects on ANPP and BNPP were different for summer‐clipped pots than for spring, and spring + summer‐clipped pots, indicating that management could be tailored to meet specific agronomic or conservation goals.