Ingestive behaviour of beef cattle offered different forms of lucerne (Medicago sativa L.)†

A change-over design was used to establish the ingestive behaviour of twelve adult Angus cows (Bos taurus), live weight (LW) of 475 ± 18 kg, while grazing luceme (Medicago sativa L.) (T₁), eating from a swath of freshly cut lucerne (T₂), or eating wilted lucerne from a swath (T₃). In the first experiment, the herbage dry matter (DM) allowance was 4-7 kg h^?1 and in T₁ the available herbage DM mass (>5 cm) was 2892 kg ha^?1. Herbage DM intake was 2.5, 1.6 and 2.0 kg h^?1 (0.53,0.35 and 0.41 kg (100 kg LW)^?1h^?1) for T₁, T₂ and T₃, respectively. Cattle grazed at 29 bites min^?1 and ate the swathed lucerne at 6 bites min^?1. Herbage DM intake per bite was 1-2, 4-9 and 6-7 (2-5,104 and 14-4 mg(kg LW)^?1)for T₁, T₂ and T₃, respectively. The DM content of the luceme was 227, 263 and 309 g kg^?1 for the same sequence. In a second experiment with luceme of available herbage DM mass of 5321 kg ha^?1 and an allowance of 7- 3 kg h^?1 cows grazed lucerne at 2-9 kg h^?1, ate freshly cut material at 21 kg h^?1 and wilted herbage at 25 kg h^?1 (0.61, 0.45 and 0.52 kg (100 kg LW)^?1h^?1), respectively. Leaf accounted for 80%, 68% and 54% of intake for T₁, T₂ and T₃, respectively. Swathing lucerne reduced the diet selectivity by forcing cattle to take large bites that required many jaw movements to form a bolus that could be swallowed. It appeared that the mechanics of bolus formation determined ingestive behaviour of cattle eating swathed herbage.     

Seasonal patterns and vertical distributions of fine roots of alfalfa (Medicago sativa L.)

Seasonal patterns and vertical distributions of alfalfa root systems were investigated with field experiments and a simulation model. We carried out root excavations on an established alfalfa stand at Davis, California, in 1982 and 1983. Thirty-six soil cores to a depth of 150 cm were taken seven times in 1982 and seventy-two soil cores to 30 cm were taken nine times in 1983 over the growth seasons. Live fine roots were recovered through six (in 1982) or seven (in 1983) procedures, including detailed hand sorting for removing debris. Our studies revealed that fine root mass was generally greatest in spring and fall and least during summer. Secondary minima were found within each harvest cycle. At all samplings, root mass declined exponentially with depth.A simulation model was developed for studying dynamics of alfalfa fine roots. The model has two components: root growth and death. Actual growth rate of fine roots was determined by potential growth rate and dependent on soil temperature, water and carbohydrate supply. Root death was controlled by the maximum death rate and influenced by soil temperature and nonstructural carbohydrate in roots. Through differential changes in simulated growth and death rates, the model predicted well the temporal and vertical distributions of fine root mass. A high amount of fine root mass was maintained in spring by rapid growth and moderate death rates. Frequent harvests reduced root mass in summer. Root mass increased in fall again due to a prolonged high growth rate. Sensitivity analyses indicated vertical distributions varied strongly with carbohydrate supply and soil temperature.     

DROUGHT-INDUCED UNKNOWN PROTEIN 1 positively modulates drought tolerance in cultivated alfalfa(Medicago sativa L.)

Alfalfa is the most widely cultivated perennial legume forage crop worldwide. Drought is one of the major environmental factors influencing alfalfa productivity. However, the molecular mechanisms underlying alfalfa responses to drought stress are still largely unknown. This study identified a drought-inducible gene of unknown function, designated as Medicago sativa DROUGHT-INDUCED UNKNOWN PROTEIN 1(MsDIUP1). MsDIUP1 was localized to the nucleus, chloroplast, and plasma membranes.Overexpression o...     

Effects of sulphur supply on the morphology of shoots and roots of alfalfa (Medicago sativa L.)

A sulphur (S)‐deficient top soil was used in a pot experiment to investigate the effect of S supply on shoot and root growth and development in alfalfa (Medicago sativa L.). The treatments consisted of three rates of addition of S: 0, 20 and 40 mg kg^?1 soil and each was replicated four times. Alfalfa was harvested at 15, 30, 45, 60 and 75 d after seedling emergence. By the end of the experiment, plants with S supply had a significantly larger leaf area, heavier leaf, shoot and root dry weight per pot than controls. The effects of adding S also significantly increased plant height, basal stem diameter, chlorophyll concentration of young leaves, root length and root surface area compared with controls. The effects of S were greater on shoots than on roots. The ratio of root to shoot dry weight was 0·47 when S was supplied and 0·88 without added S, indicating that c. 0·32 and 0·47 of the total net photosynthate, produced with or without S supply, respectively, were used for the development of roots. Overall, overcoming S deficiency resulted in a significant increase in shoot and root growth.     

Genetic diversity of some Mediterranean populations of the cultivated alfalfa (Medicago sativa L.) using SSR markers

This species study was to investigate the differentiation level among 26 populations in which 12 are locals originating from the Tunisian South and 14 introduced from Italy, Austerely, France and Morocco with two SSR markers. These highly polymorphic and co dominant markers, together with recent population genetic statistic extended to autotetraploids, offer tools to analyse genetic diversity in alfalfa. The number of alleles per locus varied between 8 and 9. The genetic similarity between these various populations is estimated by the index of Rogers and Tanimoto. Genetic diversity is analysed by two statistical procedures: Hierarchical classification and Correspondence Factorial Analysis (CFA). Four large groups were obtained.     

How planting configuration influences plant secondary metabolites and total N in tall fescue (Festuca arundinacea Schreb.), alfalfa (Medicago sativa L.) and birdsfoot trefoil (Lotus corniculatus L.): Implications for grazing management

Theories suggest that incorporating alfalfa (Medicago sativa L.; Alf) or birdsfoot trefoil (Lotus corniculatus L.; BFT) into endophyte‐infected tall fescue (Festuca arundinaceas Schreb.; E+TF) pasturelands may improve livestock production. We investigated how planting configuration might influence plant secondary metabolites (PSM) and nitrogen concentration in these forages. Total nitrogen (N), in addition to condensed tannins (CT), saponins and ergovaline (EV), was compared in BFT, Alf and E+TF, respectively, when forages grew in monocultures and all possible two‐way “mixtures” using a block design with repeated measures in three blocks. Ergovaline (p < .01) and N (p < .001) concentrations in E+TF were greater when growing adjacent to legumes than when growing in monoculture, and N and EV concentrations in E+TF were positively correlated (r = .51; p = .001). No differences in saponins or CT were found when Alf or BFT grew in monoculture or in two‐way mixtures (p > .10). We conducted an in vitro trial to determine whether CT or saponins isolated from BFT and Alf, respectively, would bind to EV in water. Ergovaline bound to saponins to a greater extent (39%; SE = 0.25) than CT (5.1%; SE = 5.13; p < .05). Because EV was lower in E+TF monocultures than in E+TF–legume mixtures, and because CT and saponins may form complexes with EV which may alleviate fescue toxicosis, animals may benefit from systems which allow them to graze monoculture patches of E+TF and Alf or BFT rather than grass–legume mixtures.     

Animal and forage responses on lucerne (Medicago sativa L.) pastures under contrasting grazing managements in a temperate climate

This study determined the impact of a change in grazing system on beef production from lucerne pastures in Argentina. One system (T500) used the traditional recommendation to commence grazing in spring when lucerne was near to 10% flowering. The grazing interval was ~ 500 growing degree-days (GDD; above a base temperature for growth of 5°C) from mid-spring to mid-autumn. In contrast, the T350 system commenced grazing 11–15 days earlier at ~ 1,000 kg DM/ha and the grazing interval was ~ 350 GDD from mid-spring to mid-summer, and from mid-summer to mid-autumn, it was ~ 500 GDD. Total live-weight production was ~ 30% or 185 and 115 kg/ha higher in T350 than T500 in Years 1 and 2 respectively. This was due to a higher live-weight production per head and a higher stocking rate, because T350 produced 1,600 kg DM ha⁻¹ year⁻¹ more forage. Plant population (~70 plants/m²) and perennial biomass (root plus crown) at the end of the second year did not differ between treatments. This suggests that lucerne persistence was not affected by the more intensive spring grazing of T350, because an adequate period of autumn recovery was allowed. This work quantified the live-weight gain (+30%, +150 kg/ha) when the grazing management of lucerne during the spring–summer period was based on crop growth status (i.e. standing biomass, canopy height) rather than on crop phenology.     

Supplementary feeding of grazing beef cattle

The effects of cereal and protein supplements on feed intake and liveweight gain were studied. In 1975, steers were continuously stocked on autumn pasture and fed no supplement or 8 g dry matter (DM) per kg liveweight (LW) per d as rolled barley (crude protein (CP) concentration 120 g kg^-1), lucerne cobs (CP concentration 190 g kg^-1) or a mixed concentrate (CP concentration 300 g kg^-1). In 1976, steers were continuously stocked or rotationally grazed in summer and fed no supplement or 7 g DM per kg LW per d as either rolled barley (CP concentration 130 g kg^-1) or a mixture of rolled barley and groundnut meal (CP concentration 210 g kg^-1). Herbage organic matter (OM) intakes in 1975 and 1976 were depressed on average by 22 and 15% respectively with supplementation, but total OM intakes were increased by 9 and 15% respectively. Daily liveweight gain was not significantly increased by supplementation in 1975 when herbage allowance was ample but was significantly increased in 1976 when herbage allowance was limited and herbage digestibility was lower. Protein concentration of the concentrate did not significantly affect daily gain in either year nor was there any difference in gain between rotational grazing and continuous stocking.     

In vitro direct plant regeneration and Agrobacterium‐mediated transformation of lucerne (Medicago sativa L.)

In vitro direct plant regeneration of lucerne was achieved by simultaneous application of thidiazuron (TDZ) and 6‐benzyladenine (BA) in Murashige and Skoog (MS) medium. Seedlings were germinated and grown for 6 d on growth regulator–containing MS medium. The shoot tip, consisting of the apical meristem along with parts of the cotyledonary leaves and hypocotyl, was then cultured on a medium containing the growth regulator(s). Adventitious budding of the shoot tip was promoted synergistically by treatment with TDZ and BA, and a maximum of thirty‐five shoots per explant was obtained on a medium supplemented with 2 mg L^?1 TDZ and 1 mg L^?1 BA. Plant regeneration frequency varied from 67 to 93%, and five Indian lucerne cultivars responded well to the regeneration protocol. The Agrobacterium‐mediated transformation frequency from co‐cultivated explants was 13% following multiple shoot induction. Southern analysis of the T₀ plants and T₁ progenies confirmed stable inheritance of the hpt marker gene. Agrobacterium infection of the explant caused a significant reduction in the plant regeneration frequency (23%) and the number of shoots induced (11) when compared with uninfected explants. A single shoot tip provided sufficient material to regenerate and establish twenty‐seven lucerne plants, whereas only nine plants could be regenerated from an Agrobacterium co‐cultivated explant. This transformation protocol could represent a valuable improvement over existing ones for lucerne.     

Allowance-intake relations of cattle grazing vegetative tall fescue†

Herbage allowance is one of the important pasture factors in the determination of intake by grazing livestock. Ingestive behaviour of 12 adult Angus cows (Bos taurus) was measured over a range of allowances (0·25 to 0·72 kg dry matter (DM) per 100 kg live weight (LW) for a 1-h period) of vegetative tall fescue (Festuca arundinacea Schreb.). A balanced change-over design was used to estimate direct, residual and permanent effects of herbage allowance on rate of DM intake, rate of biting and herbage DM intake per bite. In Experiment 1, herbage DM intake per meal increased linearly from 0·68 to 1·72 kg (100 kg LW)^?1 as DM allowance increased from 0·25 to 0·72 kg (100 kg LW)^?1 h^?1. Cows grazed at ·30 kg (100 kg LW)^?1 h^?1 and stopped grazing when the sward was reduced to a height about 10 to 12 cm above the soil surface, approximately defined by the tops of pseudostems. In Experiment 2, herbage DM intake rates of 0·29, 0·47 and 0·42 kg (100 kg LW)^?1 h^?1 were recorded as cows grazed allowances of 0·43, 0·70 and 0·90 kg (100 kg LW)^?1 h^?1 for most of the 1-h grazing period. Limiting herbage DM allowances in Experiment 2 were associated with small reductions in rate of biting and herbage DM intake per bite as allowance declined. Sward DM density (>5 cm) was an important variable in the determination of herbage DM intake rates at lower herbage allowances.     

Effects of tractor wheeling on root morphology and yield of lucerne (Medicago sativa L.)

The purpose of this study was to determine the effect of soil compaction on the herbage yield and root growth of lucerne ( Medicago sativa L.). A field experiment was conducted on a silty loam Mollic Fluvisols soil in 2003–2006. Herbage yield and root morphology, in terms of root length density, mean root diameter, specific root length and distribution of dry matter (DM) in roots, were measured. Four compaction treatments were applied three times annually by tractor using the following number of passes: control without experimental traffic, two passes, four passes and six passes. The tractor traffic changed the physical properties of the soil by increasing bulk density and penetration resistance. Soil compaction also improved its water retention properties. These changes were associated with changes in root morphology and distribution of the DM in roots. Soil compaction resulted in higher proportions of the DM in roots, especially in the upper, 0–10 cm, soil horizon. Decreases in the root length density were observed in a root diameter range of 0·1–1·0 mm. It was also found that roots in a more compacted soil were significantly thicker. An effect of the root system of lucerne on soil compaction was observed. The root system of lucerne decreased the effects of soil compaction that had been recorded in the first and the second year of the experiment. An increase in the number of passes resulted in a decrease in the DM yield of herbage in the second and third harvests each year.     

The effects of poloxalene on ingestion by cattle grazing Lucerne†

The mechanisms that terminate meals of cattle grazing lucerne (Medicago sativa L.) are not well defined. Sub-acute bloat may lead to cessation of grazing and, consequently, surface active substances used in the treatment and prevention of bloat, such as poloxalene, may extend grazing meals and increase herbage intake. Twelve mature Angus cows (Bos taurus) were offered 0, 12·5 and 25·0 g poloxalene in 0·5 kg of crushed maize (Zea mays L.) kernels each day, immediately before two consecutive 1-h measured parts of a grazing meal on 21- to 24-day-old lucerne swards with a herbage dry matter (DM) mass (> 5 cm) of 2·03 t ha^?1 and herbage DM mass allowance of 3·55 kg hd^?1h^?1. Total herbage DM intake was 2·52 kg hd^?1 during the first hour and 1·54 kg hd^?1 during the second hour of the 2-h grazing meal. Differences in herbage intake were attributable to a cessation of grazing. Mean rates of biting were 26·3 and 14·8 bites min^?1 and mean DM intakes per bite were 1·82 and 4·38 g during the first and second part of meals, respectively. Poloxalene treatments caused a small linear decline in grazing time during the first part of meals and a larger increase in grazing time during the second part of meals. Lower rates of DM intake caused by poloxalene were offset by increases in grazing time. It was concluded that poloxalene moderated ingestive behaviour within grazing meals of immature lucerne and this response may have been at least partly due to the relief of sub-acute bloat.     

Effects of livestock breed and rearing experience on foraging behaviour of yearling beef cattle grazing unimproved grasslands

The relative importance of breed versus rearing experience on the grazing behaviour and diet selection of beef cattle when grazing unimproved grassland was examined over 4 years. Suckler‐reared calves of a traditional (T) breed (North Devon) or a commercial (C) breed (Simmental × Hereford Friesian) were cross‐fostered and then reared either extensively (E) on unimproved grassland or intensively (I) on agriculturally improved fertilized grassland. As yearlings, the four groups of calves (Traditional breed + Extensive rearing (TE); Traditional breed + Intensive rearing (TI); Commercial breed + Extensive rearing (CE) and Commercial breed + Intensive rearing (CI)) grazed unimproved grassland dominated by Molinia caerulea, for 2 months, and foraging behaviour was studied in a test phase. There was a breed effect on total (bites + chews; TJM) jaw movement rate (T, 78·2 vs. C, 76·5 min^?1; F prob. = 0·041) during grazing and on the proportion of bites taken from plant communities with sward height ≥6 cm (T, 0·83 vs. C, 0·76; F prob. = 0·018). Rearing experience affected TJM rate in the first year in July (E, 80·0 vs. I, 76·8 min^?1; F prob. = 0·015) and August (E, 78·5 vs. I, 75·5 min^?1; F prob. = 0·046). The intensively reared animals grew less well on average during the test phase than those that had previous experience of the unimproved grassland as calves with their mothers (E, 0·16 vs. I, 0·09 kg day^?1; F prob. = 0·033). Our findings indicate that the rearing experience of livestock appears to be as important as the breed when designing grazing managements for nature conservation areas.     

Acoustic measurement of intake and grazing behaviour of cattle

Acoustic analysis of grazing behaviour was found to allow accurate identification of chewing and biting, and estimation of intake by cattle. Four steers grazed six types of turves, three were short (14, 16 and 20 cm tall), leafy turves from mowed Setaria lutescens with high application of N fertilizer, and three were tall (36, 49 and 62 cm tall), mature turves from uncut areas with low application of N fertilizer. Each animal grazed ten bites from each turf type while behaviour was videotaped and grazing sounds were recorded with a wireless microphone taped to the animal's forehead. The intake was measured by the difference in pre- and post-grazing turf weight, corrected for water loss. Chews and bites differed in acoustic characteristics, with bites producing more output in the 3–8 kHz frequency band. Discriminant analysis of the acoustic characteristics correctly classified chews and bites with 94% accuracy. Intake was predicted with a high degree of accuracy by total energy flux density (fJ m^–2) in chewing sounds (EFDC), EFDC per chew and average intensity of chewing sound in the 1–2 and 2–3 kHz bands ( R ²=0·90, CV=3·6%). Although bite mass ranged from 1·37 to 4·50 g, EFDC per g of intake (CV=0·015) was not affected by treatments or animals. Chewing sounds carried more information about intake than biting sounds and chews per bite. Analysis of grazing sounds has the potential to overcome many of the problems associated with the measurement of grazing intake.     

Short-term fasts and the ingestive behaviour of grazing cattle

Twelve tethered Angus cows (Bos taurus) weighing 471 ± 18 kg were used in a balanced changeover design to estimate the direct (D), residual (R), and permanent (P) effects of 1,2, and 3 h fasts following 2 h grazing sessions on the ingestive behaviour of cattle grazing swards of endophyte- (Acremonium coenophialum Morgan-Jones and Gams)-free tall fescue (Festuca arundinacea Schreb. cv Kentucky 31) (Exp I) and lucerne (Medicago sativa L. cv Arc) (Exp II). Herbage dry-matter (DM) mass (> 5 cm) and individual herbage DM allowances were 1-16 t ha-1 and 50 kg per hour in Exp I and 1-861 ha-1 and 78 kg per hour in Exp II, respectively. In Exp I, P effects of fasting followed trends of R effects since the D effects were small. Mean DM intake rates (P) were 2-2., 1-8, and 1-3 kg h-1 for cows given 1, 2, and 3 h fasts, respectively. Mean intakes (DM) per bite (P) were 082, 071, and 045 g bite-1 for cows assigned 1, 2, and 3 h fasts, respectively. Rates of biting were not affected by fasting and averaged 45 bites min"'. In Exp II, P effects followed trends in D effects since R effects were small. Mean DM intake rates (P) were 20 , 22, and 3-0 kg for cows subjected to 1,2, and 3 h of fast, respectively. Rates of biting (P) were 24, 27, and 32 bites min-1 for cows after 1, 2, and 3 h fasts, respectively. DM intakes per bite (P) were not affected by fasts and averaged 1-46 g bite-1. The behavioural responses of cattle to interval between meals were attributed to differences in flow characteristics of ingesta of lucerne and tall fescue in the gastrointestinal tract.     

The effect of fasting on short-term cattle grazing behaviour

The effects of fasting on feeding behaviour, intake rates, and diet quality were studied with steers grazing vegetative Lolium multiflorum swards. Fasting interrupted the normal alternation of grazing and rumination and led to longer grazing times (0·65 vs. 0·45 of observed time), shorter rumination times (0·15 vs. 0·30 of observed time), and higher total dry matter (DM) intakes (6200 g DM vs. 3750 g DM d⁻¹)-Fasting did not affect prehended bite size which averaged 047 g DM bite⁻¹. Declining bite size within a day was explicable by changes in herbage mass. Biting rate (38.9 bites min⁻¹) and instantaneous intake rate (2675 g DM min⁻¹) of fasted animals were considerably higher than non-fasting animals in the mornings, but neutral detergent fibre (NDF) concentration of the diet (0 742 of organic matter) was generally not depressed by fasting. Consequently, non-fasted animals appeared to be feeding suboptimally since their nutrient intake rates were considerably lower than that which they are capable of exhibiting. Mastication rates per unit NDF intake were considerably lower in the morning for fasted animals (0·78 chews g⁻¹ NDF intake) which suggested that their intake rates may have led to larger ingested particle size. Therefore, on Lolium multifiorum swards, the steers attained a higher intake rate by masticating the forage less while maintaining diet quality.     

Harvest management effects on alfalfa (Medicago sativaL.) production and quality in Mediterranean areas

The effects of plant harvest stage, autumn harvest dateand cultivars on alfalfa production and quality weredetermined in a 3-year field experiment established in1992. Harvesting stage influenced annual yield andquality. Late bud-first flower harvests increased harvestfrequency and forage quality in comparison with har-vestingat the full bloom stage while decreasing dry-matteryield by 18% (25·5 vs. 21·6 t ha 21 ). Harvestingstage significantly affected autumn forage productionand quality and yield at the first spring cut. Harvests atfull bloom allowed greater autumn and spring regrowththan cutting at the late bud stage, possibly because ofthe accumulation of higher root reserves. Autumn har-vestsand cultivar significantly influenced the yields atthe first spring cut in any growing season. Cuttingbefore the first frost in autumn reduced the vigour ofboth cultivars, and the subsequent yield at the first cutin any year, in comparison with harvests taken after ornear the first autumn frost. It is concluded that theeffects of the stage of harvesting alfalfa on dry-matterproduction and quality are important in theMediterranean environment of the Ebro Valley; theeffects of autumn management were observed mainlyon the yields of the subsequent first cut in spring but noton the total annual production.     

An integrated methodology for studying short-term grazing behaviour of cattle

Grazing studies are hampered by difficulty in controlling the characteristics of that part of the sward encountered by animals. A methodology was developed to study the effects of sward height, density and spatial arrangement on bite dimensions, bite weight and instantaneous intake rate by cattle. Hand-constructed swards (HCS) consisted of tillers threaded through wooden modules and attached to a base board. The microphone of a cordless transmitter was attached to the forehead of steers before swards were grazed. HCS were bolted onto a force plate which recorded the forces exerted during grazing. Grazing sessions were videotaped. Height and density of swards were successfully controlled by hand-construction. Bite weight was determined more accurately by dry matter (DM) disappearance than by the reduction of fresh weight corrected for moisture loss and herbage DM content. Bite area and bite depth were precisely measured by counting and measuring the residual height of grazed plant parts. Bites and chews were identified and counted from the soundtrack of video tapes. Visual count of chews was inaccurate because animals can prehend new herbage and chew herbage previously gathered with the same jaw movement. Many jaw movements involve only manipulation of herbage without biting or chewing. Bite dimensions result from the physical interaction of relatively fixed motor patterns, such as tongue sweeps, with vegetation structure. Thus, bite dimensions measured by this technique are relevant to field situations.     

Accelerated drying of cut lucerne (Medicago sativa L.) by chemical treatments based on inorganic potassium salts or alkali metal carbonates

Liquid treatments to accelerate drying were applied to lucerne under laboratory conditions by brief immersion (～3s) of cut shoots. Aqueous solutions of the alkali metal carbonates Li₂CO₃, Na₂CO₃ and K₂CO₃ were found to reduce drying times to 33% moisture content (MC) on a dry weight basis (dwb) by 45%, 55% and 65% respectively. Effectiveness was related to the ionic radius of the cation. From a range of potassium salts (KCl, K₂CO₃, KHSO₄, KOH, K₂SO₄) in aqueous solution, the only useful reductions in drying time to 33% MC (dwb) came from the alkaline KOH (68%) and K₂CO₃ (65–76%). It is considered that K⁺ has a specific function in increasing water loss through the plant cuticle and that association with CO₃^2- provides the high pH necessary for this activity. An aqueous solution of K₂CO₃ (0·16 M) gave greater acceleration of drying than the organic solvent petroleum ether and no benefit was gained by combining these treatments. Addition of a surfactant did not improve the effectiveness of K₂CO₃ as a desiccant but mixing with a rape-seed oil emulsion reduced the drying time to 33% MC (dwb) by 11% relative to K₂CO₃ alone. Under field conditions K₂CO₃ as an aqueous solution gave only small reductions in the drying time to 33% MC and effectiveness was reduced by the addition of the rapeseed oil emulsion. Better results with K₂CO₃ (aq) might have been achieved with a more ventilated swath structure but the results strongly suggest that the oilseed rape emulsion is unlikely to improve the effectiveness of K₂CO₃ under field conditions.     

Influence of phosphorus and potassium fertilization on damage to alfalfa,Medicago sativa L., by the alfalfa weevil,Hypera postica (Gyllenhall) and potato leafhopper,Empoasca fabae (Harris)

In a field study, the effects of phosphorus and potassium fertilization on damage caused by the potato leafhopper, Empoasca fabae (Harris), and alfalfa weevil, Hypera postica (Gyllenhall), to alfalfa, Medicago sativa L., were studied. Potato leafhopper and alfalfa weevil populations were either controlled with insecticides or allowed to develop as untreated controls. Insect management treatments were applied to alfalfa managed under high and low soil fertility regimes. Alfalfa grown under high soil fertility appeared more favourable for alfalfa weevil populations but was able to tolerate more defoliation. Populations of alfalfa weevil larvae were 34% higher on fertilized stands. On the other hand, potato leafhopper populations were as much as 43% higher on low-fertility stands. Alfalfa weevil damage caused a carry-over effect which reduced both plant height and yield of the second cutting. Fertilization negated this effect on height but not on yield. Stands damaged by potato leafhopper recovered more slowly after harvest, but fertilization reduced this effect. Yields from first-cutting alfalfa (which is not infested by the potato leafhopper) the following year were 10% greater on fertilized stands where leafhopper control had been applied the previous season. Plots infested by potato leafhopper suffered greater yield losses under low-fertility management. Leafhopper control and fertilization, alone and in combination with one another, negated these effects.