Trifolium Michelianum Research Articles

Nitrogen Delivery from Legume Cover Crops in No‐Till Organic Corn Production

Sixteen winter annual cover crop cultivars were grown in North Carolina to determine total N accumulation, biological N fixation (BNF) potential, and compatibility with a roller‐crimper‐terminated organic corn (Zea maysL.) production system. Cover crops and termination dates were tested in a stripped block design. Treatments included hairy vetch (Vicia villosaRoth), common vetch (Vicia sativaL.), crimson clover (Trifolium incarnatumL.), Austrian winter pea (Pisum sativumL.), berseem clover (Trifolium alexandrinumL.), subterranean clover (Trifolium subterraneumL.), narrow leaf lupin (Lupinus angustifoliusL.), and Balansa clover (Trifolium michelianumSavi.), as well as bicultures of rye (Secale cerealeL.), hairy vetch, and Austrian winter pea. Roller‐crimper termination occurred in mid‐April, early May, and mid‐May. Total biomass, N concentration, and C/N ratios were determined for cover crops at all roll times and natural15N abundance at the optimal kill date. Hairy vetch and crimson clover monocultures had the greatest overall biomass in 2009, and bicultures the greatest biomass in 2010. Crimson clover successfully terminated in late April, hairy vetch and Austrian winter pea in mid‐May, and berseem clover and common vetch in late May. All cover crops except lupin and subterranean clover derived between 70 and 100% of their N from the atmosphere. Corn response to cover crop mulches was significantly affected by the time of rolling, with poor stands resulting from competition with insufficiently terminated mulches. Crimson, Balansa, and subterranean clover mulches resulted in poor corn yields despite relatively high levels of total N. The highest corn yields were achieved in hairy vetch and rye plus hairy vetch bicultures.

Vegetative and reproductive development of balansa clover

The rate of emergence, time of the first mainstem leaf appearance, phyllochron and branch initiation and inflorescence development were quantified for balansa clover (Trifolium michelianum).

Photoperiod affects the flowering time of field-sown balansa clover

Two cultivars of balansa clover (Trifolium michelianum Savi.) were sown on eight occasions from 14 October 2005 to 5 February 2007 in Canterbury, New Zealand, which gave a range of photoperiod at emergence between 8.6 and 15.7 h. The duration from emergence to flowering was related to the length and direction of change in photoperiod at the time of emergence. Thermal time (Tt) from emergence to flowering was constant at ~620 degree-days for ‘Bolta’ and ~365 degree-days for ‘Frontier’ balansa clover plants, provided they emerged into increasing photoperiods. For plants that emerged into decreasing photoperiods, Tt from emergence to flowering decreased from ~1500 to ~630 degree-days for ‘Bolta’ but was constant at ~690 degree-days for ‘Frontier’. Models are presented to predict the Tt requirement from emergence to flowering for ‘Bolta’, ‘Frontier’ and, based on reanalysed data, CPI45856 balansa clovers in relation to daylength at emergence. These results are discussed in relation to farm sowing and management practices.

Differences in yield among annual forages used by the dairy industry under optimal and deficit irrigation

While perennial forages dominate the feed base on Australian dairy farms, poor persistence of perennial ryegrass (Lolium perenne L.) and relatively poor forage nutritive value of kikuyu (Pennisetum clandestinum Hochst. ex. Chiov.) and paspalum (Paspalum dilatatum Poir.) has led to an increasing interest in growing annual forages. Thus, this study was conducted to identify annual forage species that are more productive than the commonly used perennial pasture species. Seventeen annual forages were investigated under ‘optimal’ irrigation and two deficit irrigation treatments (nominally 66 and 33% of irrigation water applied of the optimal level) over 3 years at Camden, New South Wales, on a brown dermosol in a warm temperate climate. The forages evaluated were: Italian ryegrass (Lolium multiflorum Lam.), oats (Avena sativa L.), triticale (Triticosecale rimpaui Wittm), wheat (Triticum aestivum L.), balansa clover (Trifolium michelianum Savi), berseem clover (Trifolium alexandrinum L.), maple pea (Pisum sativum L.), Persian clover (Trifolium resupinatum L. var. majus Boiss.), subterranean clover (Trifolium subterraneum L.), forage rape (Brassica napus L.), forage radish (Raphanus sativus L.), maize (Zea mays L.), Japanese millet [Echinochloa esculenta (A. Braun) H. Scholz], pearl millet [Cenchrus americanus (L.) Morrone], sorghum [Sorghum bicolor (L.) Moench], cow pea [Vigna unguiculata (L.) Walp.] and lablab [Lablab purpureus (L.) Sweet]. There was more than a 4-fold range in annual yield between forages, but the length of the growing season and season of growth made direct comparisons difficult. Under optimal irrigation, maize produced the highest mean yield of 29.0 t DM/ha in only 125 days, which was over three times greater than cow pea (9.2 t DM/ha) grown in the same season yet requiring 190 days. Of the cool season annuals, wheat had the highest mean yield of up to 20.6 t DM/ha in 230 days, which was more than three times the yield of the lowest yielding forage, subterranean clover, at only 6.5 t DM/ha in 215 days. The forages which require harvesting generally had higher yields within a growing period of similar length than those that were defoliated to reflect being ‘grazed’. Combining annual forages in an annual cycle (e.g. maize and wheat) had the potential to produce up to 47 t DM/ha. Deficit irrigation reduced annual yield of all warm season-grown forages ranging from 8% for sorghum up to 48% for maize. In contrast, annual yield reductions were generally smaller for cool season forages, there being no reduction for forage rape, subterranean clover or oats, but up to 35% for Persian clover. However, while yield is an important criterion for choosing dairy forages, it is only one factor in a complex system, and choice of forages must be considered on a whole-farm basis and include water use efficiency, nutritive value, cost of production and risk.

The influence of NaCl salinity and hypoxia on aspects of growth in Trifolium species

The effects of salinity and hypoxia on growth, nutritive value, and ion relations were evaluated in 38 species of Trifolium and 3 check legume species (Trifolium fragiferum, Trifolium michelianum, and Medicago sativa) under glasshouse conditions, with the aim of identifying species that may be suitable for saline and/or waterlogged conditions. In the first set of experiments, plants were grown hydroponically at four NaCl concentrations (0, 40, 80, and 160 mm NaCl) and harvested after exposure to these treatments for 4 weeks. NaCl concentrations up to 160 mm reduced dry matter production in most species; however, there were differences in salt tolerance among species, with T. argutum, T. diffusum, T. hybridum, and T. ornithopodioides performing well under the saline conditions (dry matter production was reduced by less than 20%). Concentrations of Na+ and Cl− in the shoots increased with increasing salinity levels, and species again differed in their capacity to limit the uptake of these ions. Dry matter digestibility at 0 mm ranged from 49.8% (T. palaestinum) to 74.0% (T. vesiculosum) and decreased with increasing NaCl concentrations. A second set of experiments evaluated the tolerance of Trifolium species to hypoxic conditions in the glasshouse. Shoot growth, and to a lesser extent root growth, were reduced in all Trifolium species when plants were exposed to stagnant, non-aerated conditions for 28 days, but T. michelianum, T. resupinatum, T. squamosum, T. nigrescens, T. ornithopodioides, T. salmoneum, and T. fragiferum were the least affected species. All species acclimated to the oxygen-depleted conditions by increasing the gas-filled porosity in the roots. This study has provided information that will assist in the identification of forage species for saline and/or waterlogged areas.

중부지역 논에서 월년생 두과 사료작물의 생육특성 및 수량 비교

This experiment was conducted to compare the agronomic characteristics, flowering condition and productivity of introduced annual legumes at paddy field of Seonghwan(Cheonan, Chungnam, Korea) from September 2006 to May 2007. Annual legumes used in this study were hairy vetch(Vicia villsa, Rosa), crimson clover(Trifolium incarnatum, Contea), berseem clover(Trifolium alexandrinum, Alexandria), persian clover(Trifolium resupinatum, Prolific), balansa clover(Trifolium michelianum, Paradona), sweet clover(Melilotus officinalis, Yellow) and forage pea(Pisum sativum, Austrian). Emergency rate after seeding were 90% or more in crimson clover, hairy vetch, forage pea and berseem clover. Wintering of hairy vetch and crimson clover were excellent as 98% and 95%, respectively. Flowering rate of harvesting date(May 10) was 100% in crimson clover, 98% in balansa clover, 5% in persian clover and others were not flowering. Fresh and dry matter yield of crimson clover were highest as 72,556 kg/ha and 16,062 kg/ha, respectively. Crude protein yield of hairy vetch was highest as 2,929 kg/ha but not significant with crimson clover(2,169 kg/ha). TDN yield of crimson clover was highest as 9,007 kg/ha but not significant with hairy vetch(7,366 kg/ha). According to the results from this study, it is suggested that crimson clover would be recommendable for autumn-sowing annual legume at paddy field of Central Provinces.

Grazing management for regeneration of balansa clover in a cocksfoot pasture

'Bolta' and 'Frontier' balansa clover seedlings were counted through two autumns following a large seed set in November 2006, from monocultures sown in a dryland environment in Canterbury. Following rain on 5 January 2007, 65% of 'Bolta' seed and 54% of 'Frontier' seed emerged. 'Bolta' and 'Frontier' balansa clover seedlings were counted through two autumns following a large seed set in November 2006, from monocultures sown in a dryland environment in Canterbury. Following rain on 5 January 2007, 65% of 'Bolta' seed and 54% of 'Frontier' seed emerged. Keywords: annual legumes, balansa clover, Dactylis glomerata, false break, seed bank, spring closing date, Trifolium michelianum, Trifolium subterraneum.

Growth and physiological responses of balansa clover and burr medic to low levels of salinity

This study investigated a wide range of morphological and physiological responses of burr medic (Medicago polymorpha L. cv. Scimitar) and balansa clover (Trifolium michelianum L. cv. Frontier) to different levels of salinity. Balansa clover and burr medic plants were grown in the greenhouse at 25°C day temperature and 16°C night temperature. Salt treatments were applied 6 weeks after germination, and plants were grown for a further 6 weeks before harvest. The salt treatments included a control, 20 mm, 40 mm, and 80 mm of NaCl. The shoot biomass yield was significantly affected by the species × salt interaction (P = 0.04). For balansa clover, the shoot biomass yield was greatest for the control treatment and lowest for the 20 mm NaCl treatment. For burr medic, the shoot biomass yield did not differ among salt treatments. Sodium (Na+) and potassium (K+) concentrations in leaves and stems increased with salinity. Compared with a non-saline control, sodium concentration in leaves in the 80 mm NaCl treatment was 3-fold higher for balansa clover and 2-fold higher for burr medic. Under various saline treatments, leaf Na+/K+ ratio stayed relatively constant in balansa clover (0.3–0.4) and burr medic (0.4–0.5), whereas stem Na+/K+ ratios for both species increased with salinity. The most sensitive parameters to salinity were Na+/K+ and Na+/Ca2+ ratios, whereas biomass, chlorophyll fluorescence, net photosynthesis, stomatal conductance, transpiration, and δ13C and δ15N discrimination were least sensitive. Therefore, accumulation of sodium in the plant tissues did not reach the threshold for causing reduction in growth.

Outcomes of the search for new perennial and salt tolerant pasture plants for southern Australia

The potential adaptation of a range of perennial pasture species to recharge environments in southern Australia is reviewed based on their performance in 20 field nurseries in a nationally coordinated project. Species were also evaluated for their suitability to discharge sites where salt and waterlogging are major restraints. Species are ranked according to their potential to be incorporated into farming systems and the scope for further breeding and selection. Medicago sativa L. (lucerne) was the most persistent of the perennial legumes across a diversity of recharge environments. Lotus corniculatus L. (birdsfoot trefoil) showed the most promise on soils prone to waterlogging. Other legumes that showed potential included Cullen australasicum (Schltdl.) J.W. Grimes (tall verbine) and Lotononis bainesii Baker (lotononis). The herb Chicoriyum intybus L. was superior to M. sativa on more acid soils. Phalaris aquatica L. (phalaris) and summer dormant cultivars of Dactylis glomerata L. (cocksfoot), Festuca arundinacea L. (tall fescue) and Lolium perenne L. (perennial ryegrass) were among the most persistent and productive of the perennial grasses. Further exploitation of temperate perennial grass germplasm with increased summer dormancy should be a priority to increase the role of these grass species in lower rainfall, summer-dry environments. Although difficult to establish, the indigenous grasses Austrodanthonia caespitosa (Gaudich.) H.P. Linder (wallaby grass) and A. richardsonii (Cashmore) H.P. Linder were persistent and showed good recruitment. They should be a priority for low rainfall, low input environments. Other grasses that showed promise were Chloris gayana Kunth (Rhodes grass), Secale montanum Guss. (mountain rye), Microlaena stipoides (Labill.) R. Br. (weeping grass), Ehrhata calcycina Sm. (veldt grass) and Bromus stamineus E. Desv. (grazing brome). For discharge environments, Melilotus siculus (Turra) Vitman ex B.D. Jacks. was one of the most salt tolerant legumes and should be a priority for further development. Medicago polymorpha L. (burr medic) appears underutilised in discharge environments. Increasing the waterlogging tolerance of this moderately salt tolerant species would further enhance its potential. Trifolium michelianum Savi. (balansa clover) owed its success in discharge areas more to ‘salt avoidance’ rather than salt tolerance per se. Melilotus sulcatus Desf., T. tomentosum L. and Lotus tenuis Waldst. & Kit. ex Willd. also had traits that may prove advantageous for discharge environments. Within the pasture grasses, Puccinellia ciliata Bor (pucinellia) was superior at sites prone to waterlogging whereas T. ponticum performed better in moderately drained saline sites.

Cross-pathogenicity of Rhizoctonia solani strains on pasture legumes in pasture-crop rotations

In Australia, in the past, pasture legumes were rotated mainly with cereals, but increasingly these rotations now involve pasture legumes with a wider range of crops, including legumes. This increasing frequency of the leguminous host in the rotation system may be associated with increased root rots in legumes in the current pasture-crop rotations. The primary aim of this study was to see whether the pathogenicity on pasture legumes of strains of Rhizoctonia solani sourced from lupins and cereals (common crops in rotation with pastures) is associated with increased incidence of root rots in pasture legumes in the disease conducive sandy soils of the Mediterranean regions of southern Australia. The second aim was to determine sources of resistance among newly introduced pasture legumes to R. solani strains originating from rotational crops as this would reduce the impact of disease in the pasture phase. Fifteen pasture legume genotypes were assessed for their resistance/susceptibility to five different zymogram groups (ZG) of the root rot pathogen R. solani under glasshouse conditions. Of the R. solani groups tested, ZG1–5 and ZG1–4 (both known to be pathogenic on cereals and legumes) overall, caused the most severe root disease across the genotypes tested, significantly more than ZG6 (known to be pathogenic on legumes), in turn significantly >ZG4 (known to be pathogenic on legumes) which in turn was >ZG11 (known to be pathogenic on legumes including tropical species). Overall, Ornithopus sativus Brot. cvs Cadiz and Margurita, Trifolium michelianum Savi. cvs Paradana and Frontier and T. purpureum Loisel. cv. Electro showed a significant level of resistance to root rot caused by R. solani ZG11 (root disease scores ≤1.2 on a 1–3 scale where 3 = maximum disease severity) while O. sativus cvs Cadiz and Erica showed a significant level of resistance to root rot caused by R. solani ZG4 (scores ≤1.2). O. compressus L. cvs Charano and Frontier, O. sativus cv. Erica, and T. purpureum cv. Electro showed some useful resistance to root rot caused by R. solani ZG6 (scores ≤1.8). This is the first time that cvs Cadiz, Electro, Frontier, Margurita and Paradana have been recognised for their levels of resistance to root rot caused by R. solani ZG11; and similarly for cvs Cadiz and Erica against ZG4; and for cvs Charano, Erica, and Electro against ZG6. These genotypes with resistance may also serve as useful sources of resistance in pasture legume breeding programs and also could potentially be exploited directly into areas where other rotation crops are affected by these R. solani strains. None of the tested genotypes showed useful resistance to R. solani ZG1–4 (scores ≥2.0) or ZG1–5 (scores ≥2.5). This study demonstrates the relative potential of the various R. solani ZG strains, and particularly ZG1–4, ZG1–5, ZG4 and ZG6 to attack legume pastures and pose a significant threat to non-pasture crop species susceptible to these strains grown in rotation with these pasture legumes. Significantly, the cross-pathogenicity of these strains could result in the continuous build-up of inoculum of these strains that may seriously affect the productivity eventually of legumes in all rotations. In particular, when choosing pasture legumes as rotation crops, caution needs to be exercised so that the cultivars deployed are those with the best resistance to the R. solani ZGs most likely to be prevalent at the location.

New annual and short-lived perennial pasture legumes for Australian agriculture—15 years of revolution

Fifteen years ago subterranean clover ( Trifolium subterraneum) and annual medics ( Medicago spp.) dominated annual pasture legume sowings in southern Australia, while limited pasture legume options existed for cropping areas of subtropical Australia. Since then a number of sustainability and economic challenges to existing farming systems have emerged, exposing shortcomings in these species and the lack of legume biodiversity. Public breeding institutions have responded to these challenges by developing 58 new annual and short-lived perennial pasture legumes with adaptation to both existing and new farming systems. This has involved commercialisation of new species and overcoming deficiencies in traditional species. Traits incorporated in legumes of Mediterranean Basin origin for the Mediterranean, temperate and southern subtropical climates of Australia include deeper root systems, protection from false breaks (germination-inducing rainfall events followed by death from drought), a range of hardseed levels, acid-soil tolerant root nodule symbioses, tolerance to pests and diseases and provision of lower cost seed through ease of seed harvesting and processing. Ten new species, French serradella ( Ornithopus sativus), biserrula ( Biserrula pelecinus), sulla ( Hedysarum coronarium), gland ( Trifolium glanduliferum), arrowleaf ( Trifolium vesiculosum), eastern star ( Trifolium dasyurum) and crimson ( Trifolium incarnatum) clovers and sphere ( Medicago sphaerocarpos), button ( Medicago orbicularis) and hybrid disc ( Medicago tornata × Medicago littoralis) medics have been commercialised. Improved cultivars have also been developed of subterranean ( T. subterraneum), balansa ( Trifolium michelianum), rose ( Trifolium hirtum), Persian ( Trifolium resupinatum) and purple ( Trifolium purpureum) clovers, burr ( Medicago polymorpha), strand ( M. littoralis), snail ( Medicago scutellata) and barrel ( Medicago truncatula) medics and yellow serradella ( Ornithopus compressus). New tropical legumes for pasture phases in subtropical cropping areas include butterfly pea ( Clitoria ternatea), burgundy bean ( Macroptilium bracteatum) and perennial lablab ( Lablab purpureus). Other species and cultivars of Mediterranean species are likely to be released soon. The contributions of genetic resources, rhizobiology, pasture ecology and agronomy, plant pathology, entomology, plant chemistry and animal science have been paramount to this success. A farmer survey in Western Australia has shown widespread adoption of the new pasture legumes, while adoption of new tropical legumes has also been high in cropping areas of the subtropics. This trend is likely to increase due to the increasing cost of inorganic nitrogen, the need to combat herbicide-resistant crop weeds and improved livestock prices. Mixtures of these legumes allows for more robust pastures buffered against variable seasons, soils, pests, diseases and management decisions. This paper discusses development of the new pasture legumes, their potential use and deficiencies in the current suite.

Cover crop effect on soil carbon fractions under conservation tillage cotton

Cover crops may influence soil carbon (C) sequestration and microbial biomass and activities by providing additional residue C to soil. We examined the influence of legume [crimson clover ( Trifolium incarnatum L.)], nonlegume [rye ( Secale cereale L.)], blend [a mixture of legumes containing balansa clover ( Trifolium michelianum Savi), hairy vetch ( Vicia villosa Roth), and crimson clover], and rye + blend mixture cover crops on soil C fractions at the 0–150 mm depth from 2001 to 2003. Active fractions of soil C included potential C mineralization (PCM) and microbial biomass C (MBC) and slow fraction as soil organic C (SOC). Experiments were conducted in Dothan sandy loam (fine-loamy, kaolinitic, thermic, Plinthic Kandiudults) under dryland cotton ( Gossypium hirsutum L.) in central Georgia and in Tifton loamy sand (fine-loamy, siliceous, thermic, Plinthic Kandiudults) under irrigated cotton in southern Georgia, USA. Both dryland and irrigated cotton were planted in strip tillage system where planting rows were tilled, thereby leaving the areas between rows untilled. Total aboveground cover crop and cotton C in dryland and irrigated conditions were 0.72–2.90 Mg C ha −1 greater in rye + blend than in other cover crops in 2001 but was 1.15–2.24 Mg C ha −1 greater in rye than in blend and rye + blend in 2002. In dryland cotton, PCM at 50–150 mm was greater in June 2001 and 2002 than in January 2003 but MBC at 0–150 mm was greater in January 2003 than in June 2001. In irrigated cotton, SOC at 0–150 mm was greater with rye + blend than with crimson clover and at 0–50 mm was greater in March than in December 2002. The PCM at 0–50 and 0–150 mm was greater with blend and crimson clover than with rye in April 2001 and was greater with crimson clover than with rye and rye + blend in March 2002. The MBC at 0–50 mm was greater with rye than with blend and crimson clover in April 2001 and was greater with rye, blend, and rye + blend than with crimson clover in March 2002. As a result, PCM decreased by 21–24 g CO 2–C ha −1 d −1 but MBC increased by 90–224 g CO 2–C ha −1 d −1 from June 2001 to January 2003 in dryland cotton. In irrigated cotton, SOC decreased by 0.1–1.1 kg C ha −1 d −1, and PCM decreased by 10 g CO 2–C ha −1 d −1 with rye to 79 g CO 2–C ha −1 d −1 with blend, but MBC increased by 13 g CO 2–C ha −1 d −1 with blend to 120 g CO 2–C ha −1 d −1 with crimson clover from April 2001 to December 2002. Soil active C fractions varied between seasons due to differences in temperature, water content, and substrate availability in dryland cotton, regardless of cover crops. In irrigated cotton, increase in crop C input with legume + nonlegume treatment increased soil C storage and microbial biomass but lower C/N ratio of legume cover crops increased C mineralization and microbial activities in the spring.

Nitrogen fixation in six forage legumes in Mediterranean central Chile

The contribution of biological nitrogen fixation (BNF) to the N nutrition of six annual forage legumes, subterranean clover (Trifolium subterraneum), burr medic (Medicago polymorpha), balansa clover (Trifolium michelianum), Persian clover (Trifolium resupinatum), yellow serradela (Ornithopus compressus), and pink serradela (Ornithopus sativus) was evaluated by the 15N natural abundance technique, using four grass species (Briza máxima, Bromus mollis, Hordeum berteroanum, Avena barbata) and two composite species (Leontodon leysseri and Hedipnois cretica) as reference plants. An additional objective was to determine whether alternative legume species to those in common use (T. subterraneum and M. polymorpha) in the area, could improve BNF. The field studies were conducted in two edaphic conditions, granitic (Entisol) and clay (Vertisol) soil, located in Cauquenes, VII Region, in the sub-humid Mediterranean zone of Chile. In the granitic soil the percentages of N derived from fixation were high in all species (74 to 94%); yellow serradela cv. Tauro presented the greatest N content in dry matter and N fixation, equivalent to 91 kg N ha−1. In contrast, pink serradela cv. Cádiz and subterranean clover cv. Gosse presented the lowest N fixation. In the clay soil, under periodically waterlogged conditions, balansa clover cv. Paradana and persian clover cv. Prolific had high percentage values of BNF (>95%) and fixed more N (100.2 and 82.5 kg N ha−1, respectively) than burr medic and subterranean clover cv. Gosse. The present study allowed the identification of new germplasm of high capacity of N fixation which is an additional criterion for selecting species for infertile and waterlogged soil conditions in the Mediterranean area of Chile.

Conservation Tillage and Cover Crop Influences on Cotton Production on a Southeastern U.S. Coastal Plain Soil

Understanding cover crop and tillage system interactions within specific environments can help maximize productivity and economic returns of cotton (Gossypium hirsutum L.) produced on sandy coastal plain soils of the southeastern USA. A strip‐plot design with three replications was used to evaluate the cover crops Austrian winter pea [Pisum sativum L. ssp. arvense (L.)], balansa clover (Trifolium michelianum Savi), crimson clover (Trifolium incarnatum L.), hairy vetch (Vicia villosa Roth subsp. villosa), oil seed radish (Raphanus sativus L.), black oat (Avena strigosa Schreb.), and rye (Secale cereale L.) and tillage (strip and none) influences on cotton grown on a Bonifay fine sand (loamy, siliceous, subactive, thermic Grossarenic Plinthic Paleudults) near Waynesboro, GA from 1999 to 2003. Drought influenced production 3 of 4 yr. Cover crop biomass was greatest from rye, intermediate from black oat, oilseed radish, hairy vetch, and Austrian winter pea. Hairy vetch and Austrian winter pea contained more than 80 kg N ha−1 while other cover crops averaged <40 kg N ha−1. Cotton yields following black oat and rye had returns above variable costs ha−1 $461 and $406, respectively. Strip‐tillage increased yields by 192 kg ha−1 and annual returns by $112 ha−1 over no‐tillage, most likely due to improved available water. Combining strip‐tillage with black oat was the best combination for maximizing profit. Using black oat with strip‐tillage could increase cotton profit by $50 to $75 ha−1 compared to systems using rye on the 1.45 million ha of cotton where conservation systems have been adopted.

Sub clover, cocksfoot and lucerne combine to improve dryland stock production

The temporal (seasonal) pattern of dryland pasture and stock production from four cocksfoot based pastures (mixed with balansa, Caucasian, subterranean or white clover), a ryegrass/white clover pasture and a pure lucerne crop were compared over 2 years (2004/05 and 2005/ 06). Subterranean clover with cocksfoot provided high legume content pasture giving higher stock production than other pasture mixtures from August to October. This complemented the high yields and stock production provided by lucerne from mid September to January in 2004/05. However, a dry winter followed by spring snow resulted in lucerne production similar to other pastures in 2005/06. Cocksfoot based pastures provided more maintenance feed than perennial ryegrass during a dry summer (2005/06) but ryegrass/white clover provided higher stock production in wet summer conditions (2004/ 05). These results suggest a range of pasture species are necessary to cope with the seasonal climate variability typically experienced in dryland farm systems. Keywords: balansa clover, Caucasian clover, Dactylis glomerata, Lolium perenne, Medicago sativa, pasture growth rates, ryegrass, sheep production, Trifolium ambiguum, Trifolium michelianum, Trifolium repens, Trifolium subterraneum, white clover

Forage Legume Regeneration from the Soil Seed Bank in Western North Dakota

Rotating wheat (Triticum spp.) with fallow cannot be sustained in the Great Plains. Replacing fallow with legume pasture enhanced wheat production in Australian ley farming. The legume species used in ley farming regenerated from seed produced during previous pasture periods. Our objective was to identify legumes that regenerated from the seed bank in western North Dakota. Ten legume species were established in one experiment, 30 species in a second experiment, and 29 species in a third experiment. Seedlings were counted in the spring following the year of establishment. Over 200 seedlings m−2 germinated in balansa clover (Trifolium michelianum Savi), berseem clover (T. alexandrinum L.), birdsfoot trefoil (Lotus corniculatus L.), black medic (Medicago lupulina L.), burr medic (M. polymorpha L.), crimson clover (T. incarnatum L.), Persian clover (T. resupinatum L.), and red clover (T. pratense L.) plots in at least one experiment. Forage dry matter yield ranged from 2 to 5 Mg ha−1 for birdsfoot trefoil and red clover depending on the experiment and was similar to forage yield by alfalfa (M. sativa L.) that persisted in the second year following establishment (P > 0.05). Crude protein, acid detergent fiber, and neutral detergent fiber concentrations suggested that forage quality was equal or superior for birdsfoot trefoil compared with alfalfa and red clover. Birdsfoot trefoil has potential as a self‐seeding pasture species in the Great Plains.

Influence of cover crops on insect pests and predators in conservation tillage cotton.

In fall 2000, an on-farm sustainable agricultural research project was established for cotton, Gossypium hirsutum L., in Tift County, Georgia. The objective of our 2-yr research project was to determine the impact of several cover crops on pest and predator insects in cotton. The five cover crop treatments included 1) cereal rye, Secale cereale L., a standard grass cover crop; 2) crimson clover, Trifolium incarnatum L., a standard legume cover crop; 3) a legume mixture of balansa clover, Trifolium michelianum Savi; crimson clover; and hairy vetch, Vicia villosa Roth; 4) a legume mixture + rye combination; and 5) no cover crop in conventionally tilled fields. Three main groups or species of pests were collected in cover crops and cotton: 1) the heliothines Heliothis virescens (F.) and Helicoverpa zea (Boddie); 2) the tarnished plant bug, Lygus lineolaris (Palisot de Beauvois); and 3) stink bugs. The main stink bugs collected were the southern green stink bug, Nezara viridula (L.); the brown stink bug, Euschistus servus (Say); and the green stink bug, Acrosternum hilare (Say). Cotton aphids, Aphis gossypii Glover, were collected only on cotton. For both years of the study, the heliothines were the only pests that exceeded their economic threshold in cotton, and the number of times this threshold was exceeded in cotton was higher in control cotton than in crimson clover and rye cotton. Heliothine predators and aphidophagous lady beetles occurred in cover crops and cotton during both years of the experiment. Geocoris punctipes (Say), Orius insidiosus (Say), and red imported fire ant, Solenopsis invicta Buren were relatively the most abundant heliothine predators observed. Lady beetles included the convergent lady beetle, Hippodamia convergens Guérin-Méneville; the sevenspotted lady beetle, Coccinella septempunctata L.; spotted lady beetle, Coleomegilla maculata (DeGeer); and the multicolored Asian lady beetle, Harmonia axyridis (Pallas). Density of G. punctipes was higher in cotton fields previously planted in crimson clover compared with control cotton fields for all combined sampling dates in 2001. Intercropping cotton in live strips of cover crop was probably responsible for the relay of G. punctipes onto cotton in these crimson clover fields. Density of O. insidiosus was not significantly different between cover crop and control cotton fields. Lady beetles seemed to relay from cover crops into cotton. Conservation of the habitat of fire ants during planting probably was responsible for the higher density of red imported fire ants observed in all conservation tillage cotton fields relative to control cotton fields. Reduction in the number of times in which economic thresholds for heliothines were exceeded in crimson clover and rye compared with control fields indicated that the buildup of predaceous fire ants and G. punctipes in these cover crops subsequently resulted in reduction in the level of heliothines in conservation tillage cotton with these cover crops compared with conventional tillage cotton without cover crops.

Genetic variability and heritability estimates for hardseededness and flowering in balansa clover (Trifolium michelianum Savi) populations

Suitability of annual pasture legume species like balansa clover (Trifolium michelianum Savi) in southern Australian farming systems depends on their hardseededness and time to flowering. Late maturing varieties with increased rate of hardseed breakdown, particularly in the late summer—early autumn period are desirable to ensure reliable regeneration in permanent pastures. Two half-sib family balansa clover populations were used to estimate heritability for the rate of breakdown of hardseededness and time to flowering. High narrow-sense heritability estimates (90.5–96.1%, rate of hardseed breakdown; 85.9–94.5%, time to flowering) were obtained, and were mainly attributed to additive gene effects. There was no relationship between rate of hardseed breakdown and time to flowering in Group1 half-sib family, which indicated that selection for both traits could be undertaken independently. In half-sib family Group 2 the relationship between the two traits suggested the possibility of selecting late maturing cultivars with increased rate of hardseed breakdown. Significant differences in time to flowering and rate of hardseed breakdown both within and between the two half-sib family groups suggested that phenotypic recurrent selection would be effective in improving the traits in these populations.

Performance of annual pasture legumes in cropping rotations in the cool temperate zone of south-eastern Australia

The relative performance of 3 alternative pasture legumes, in comparison with subterranean clover, grown in a 1:1 pasture:crop rotation was investigated during 1997–2001, at 2 sites in the high rainfall (>500 mm/year) zone of southern Australia. Seedling densities of the pasture legumes (before and after crop) were examined, along with herbage dry matter production, growth pattern and seed production. After 2 cycles of a 1:1 pasture:crop rotation, average seedling densities of balansa (Trifolium michelianum Savi var. michelianum), Persian (T. resupinatum L. var. resupinatum Gib. and Belli), arrowleaf (T. vesiculosum Savi.) and subterranean (T. subterraneum L.) clovers at the 2 sites were 6810, 2910, 680 and 630 plants/m2, respectively. Average cumulative herbage mass in 2001 was 7.49, 5.21, 8.53 and 7.76 t DM/ha.year, respectively. All clovers produced a large seed pool: balansa, 71.8 g/m2; subterranean, 38.9 g/m2; Persian, 35.5 g/m2; and arrowleaf, 35.4 g/m2. The results suggest that a 1:1 pasture:crop rotation is sustainable, in terms of pasture seed–seedling dynamics for each of the legumes, and that under this system the pasture legumes need to be sown only once.

Nodulation and growth of pasture legumes with naturalised soil rhizobia.2. Balansa clover (Trifolium michelianum Savi)

Balansa clover (Trifolium michelianum Savi) is grown widely across southern and eastern Australia. The presence of suitable rhizobia (Rhizobium leguminosarum bv. trifolii) for this species of clover, and their ability to form an effective symbiosis, was assessed in a survey of 43 soils collected from across Australia. The effectiveness of the soil rhizobia is compared with that of strains WU95 and WSM409. The study confirmed the widespread occurrence of clover rhizobia in Australian soils. No clover rhizobia were detected in 6 of the 43 soils and this was probably associated with a history of clover absence at these soil locations. Thirty of the soils contained more than 500 rhizobia per gram. These rhizobia varied from highly effective for soil T2 (128% of WSM409) through to ineffective for soil V9 (22% of WSM409). Few soil inoculants were more effective than strain WSM409. Commercial inoculant strain WSM409 was generally more effective than former inoculant strain WU95.The suboptimal performance of the rhizobia in many of the soils indicates that there is an opportunity to improve the level of nitrogen fixation by balansa clover in the field. Bearing in mind the difficulties associated with the introduction and persistence of applied inoculant strains, cultivar selection is considered as an approach to improve the symbiosis. However, this study indicated little variation in the performance of the 3 commercial cultivars, Frontier, Paradana and Bolta, in this regard.