Interaction between water-soluble carbohydrate reserves and defoliation severity on the regrowth of perennial ryegrass (Lolium perenne L.)-dominant swards

A field-study was undertaken in Hamilton, New Zealand to determine if there was an interaction between water-soluble carbohydrate (WSC) reserve content and defoliation severity on the regrowth of perennial ryegrass-dominant swards during winter. Perennial ryegrass plants with either low or high WSC content were obtained by varying the defoliation frequency. At the third defoliation at the one-leaf stage and at the first defoliation at the three-leaf stage (harvest H₁), swards were mown with a rotary lawnmower to residual stubble heights of 20, 40 or 60 mm. All swards were then allowed to regrow to the three-leaf stage before again defoliating to their treatment residual stubble heights (H₂). Frequently defoliated plants contained proportionately between 0·37 and 0·48 less WSC in the stubble after defoliation, depending on the severity of defoliation. There was no interaction between WSC content and defoliation severity for herbage regrowth between harvests H₁ and H₂. Herbage regrowth was lower from swards containing low WSC plants compared with high WSC plants (2279 vs. 2007 kg DM ha⁻¹). Furthermore, swards defoliated to 20 or 40 mm had greater herbage regrowth compared with those defoliated to 60 mm (2266, 2249 and 1914 kg DM ha⁻¹ for swards defoliated to residual stubble heights of 20, 40 and 60 mm, respectively). Regrowth of perennial ryegrass was positively correlated with post-defoliation stubble WSC content within defoliation severity treatment, implying that WSC contributed to the defoliation frequency-derived difference in herbage yield. However, the effect of defoliation severity on herbage regrowth was not associated with post-defoliation stubble WSC content.     

Water-soluble carbohydrates in perennial ryegrass breeding

Perennial ryegrasses showing genetic differences in water-soluble carbohydrate content (WSC) were assessed for dry matter digestibility (DMD), crude protein (CP) and dry matter production (DM) in both spaced plant and small plot trials. Among 100 accessions grown as spaced plants there appeared to be more genetic variation for WSC than for DMD or CP. In both spaced plants and plots, WSC was consistently positively correlated with DMD, negatively correlated with CP and showed little correlation with DM. Correlations between CP and DMD were rather inconsistent and some negative correlations were obtained between CP and DM, suggesting that environmental effects, particularly with regard to nitrogen availability, affected CP more than WSC content. It was concluded that there is considerable potential for using ryegrasses with high WSC contents to develop varieties with improved feeding value without sacrificing production.     

The effect of companion perennial ryegrass cultivars on red clover productivity when timing of the first cut is varied

Replicated plots of Hungaropoly red clover were sown on a sterilized area in May 1975 alone (seed rate 11 kg ha^-1) or with one of six cultivars of perennial ryegrass (seed rate 3·5 kg ha^-1) viz. Cropper and S24 (early heading), Barlenna and Hora (medium heading) and Melle and Perma (late heading). In 1976 and 1977 primary growth was cut at one of four dates ranging from mid-May to mid-June and thereafter plots were harvested twice each year.
Varying the time of first cut did not have a significant effect on total dry matter (DM) yield in either year despite differences in means of cutting treatments on annual red clover yields of the order of 6–9%.
In some companion grass treatments total DM yield in 1976 was increased and total red clover yield and percentage red clover contribution were reduced relative to swards sown only with red clover. In 1977 a similar but non-significant trend was found. Swards containing early ryegrasses had higher total herbage DM yields but lower red clover yields and contents than all other swards at the first harvest in both years.
Delay in date of taking the first harvest in 1976 reduced DM digestibility in the first cut and increased it in the second in both years.
It is suggested that by cutting early and increasing the number of harvests from three to four per year, differences in the content of red clover between the first and second cut might be reduced, and it is concluded that more benefit is derived from red clover when medium or late heading ryegrasses are used as companion grasses.     

The effect of the brown midrib-3 gene on the maturity and yield of forage maize

Results from two trials with normal and brown midrib-3 (bm₃) types of LG11, Inra 188, Inra 240 and Inra 258 showed the bm₃ mutant gene delayed silking by an average of 3 days, decreased whole plant dry matter (DM) concentration by 20 g kg⁻¹ and the proportion of ear by 4·6 percentage units. Comparable yields of DM were obtained from normal and bm₃ crops. The organic matter digestibility and yield of digestible organic matter of the bm₃ plants was 0.06 units and 14% higher respectively than their normal counterparts.
Measurement of the physical strength and resistance to lodging of normal and bm₃ plants showed the bm₃ gene reduced stem strength, which was highly correlated to stem diameter, stem weight and rind thickness. However, the major difference in plant lodging was between genotypes with Inra 240 plants less resistant to lodging than other genotypes. These results show that although the bm₃ gene slightly increased lodging, genotype susceptibility is the major contributing factor to plant lodging.     

Effect of herbage water-soluble carbohydrate content and weather conditions at ensilage on the fermentation of grass silages made on commercial farms

A total of 1009 samples of silage made in bunker silos on commercial farms between 1972 and 1978 was analysed to investigate the effect of herbage water-soluble carbohydrate content (WSC) and weather conditions at ensilage on fermentation as measured by ammonia-N concentration and pH of first-cut grass silages.
Silage dry matter (DM) content had the major effect on fermentation. Factors influencing silage DM were rainfall and hours of sunshine during silage making, and DM content of the grass cut. WSC content of herbage ensiled also had a significant effect on subsequent fermentation. The major influences on herbage WSC were hours of sunshine and rainfall during the growing season.
The effect of chemical additives, albeit at poorly defined and often inadequate rates, was small in comparison to that of silage DM.
The minimum DM necessary to produce well-fermented silage without additive was approximately 260 g kg⁻¹. Use of formic acid significantly reduced this requirement to 240 g kg⁻¹ and to 252 g kg⁻¹ for sulphuric add + formalin. The results indicate that the minimum herbage WSC necessary to prevent a clostridial fermentation developing in silage with a DM content of 230 g kg⁻¹ is approximately 37 g kg⁻¹ without additive and 30 g kg⁻¹ with formic acid.
It is concluded that on commercial farms, weather conditions i.e. amount of rainfall and sunshine prior to and at ensilage, have a greater effect on subsequent silage fermentation than additive use.     

Responses of C3 and C4 grasses to application of nitrogen and phosphorus fertilizer at two dates in the spring

In grasslands composed of C₃ and C₄ plants, a different pattern of response by the two photosynthetic types to fertilizer may change the floristic composition of the community. In this study, we evaluated the effects of an application of nitrogen (N) and phosphorus (P) fertilizer at two dates in the spring on the aerial growth of C₃ and C₄ grasses. Danthonia montevidensis and Stipa neesiana ( C₃), and Setaria geniculata and Sporobolus indicus (C₄), were selected from a native grassland of the Flooding Pampa, Argentina. Two consecutive experiments (early and late spring) were conducted in pots filled with the local soil. The C₃ grasses showed no response in aerial biomass, and only minor responses in aerial concentrations of N and P, numbers of leaves and tillers, and nutrient use efficiency to an application of P or N fertilizer. In contrast, their C₄ counterparts showed a consistent positive response. C₄ species performance was considerably influenced by date of fertilizer application in the spring. There was on average a 1·8 and a 2·5 increase in aerial biomass in early and late spring, respectively, to fertilizer application. The later date in spring was associated with higher ambient temperatures and it appeared that temperature rather than fertilizer application was the main limiting factor for C₃ species. It was concluded that the positive response in C₄ species to an application of P and N fertilizer indicates that the differences between C₃ and C₄ species were related to a higher demand to sustain greater growth rates in C₄ species.     

The composition of first-cut grass for ensilage in England and Wales from 1988 to 1991

A total of 2225 samples of herbage, typical of that taken for first-cut silage on commercial farms in England and Wales, was taken between 1988 and 1991. Samples were analysed for dry matter (DM), water soluble carbohydrate (WSC), crude protein (CP) and metabolizable energy calculated from modified acid detergent fibre. The results were used to investigate the effect of weather conditions upon herbage quality for ensilage. In general, in areas of high rainfall, i.e. western areas, herbage DM and WSC were significantly lower than in eastern areas, whilst the reverse situation occurred with CP. Italian ryegrass (IRG) had a significantly higher WSC and lower CP than other grasses, whilst samples from permanent pasture (PP) had significantly lower DM and WSC, and significantly higher CP than other grasses. It was calculated that to produce a WSC concentration in the fresh grass of 37 g kg⁻¹, to produce well-fermented silage without additive use, IRG grown in the east would require a DM of 160 g kg⁻¹, In contrast PP grown in the west would require a DM content of 250 gkg⁻¹.     

水稻黄叶早衰突变体osyes1的生理特性和基因定位

【目的】叶片是水稻进行光合作用最重要的器官。叶色突变体是研究光合作用、叶绿素合成代谢和叶绿体发育的重要材料。【方法】利用⁶⁰Co辐射诱变中籼恢复系自选1号,获得黄叶早衰突变体osyes1。幼苗期对突变体和野生型进行外源H₂O₂处理。抽穗期对突变体和野生型叶片进行超氧化物歧化酶活性、过氧化氢酶活性、活性氧含量、丙二醛含量、可溶性蛋白含量、叶绿素含量、净光合速率测定以及透射电镜观察。成熟期考查突变体和野生型的主要农艺性状。以osyes1/02428的F₂群体中的隐性单株为作图群体,利用图位克隆方法定位OsYES1基因。【结果】osyes1的突变性状始于3~4叶期,水稻抽穗后,所有叶片均表现为黄叶衰老症状,致使突变体株高、穗长、每穗粒数及结实率极显著低于野生型对照。与野生型对照相比,突变体幼苗对外源H₂O₂更敏感。生理分析表明,孕穗期野生型倒3叶的叶绿素含量、过氧化物酶和过氧化氢酶活性极显著低于倒2叶和剑叶,而突变体的含量则极显著低于野生型且依次极显著降低;与野生型相比,突变体剑叶、倒2叶和倒3叶的丙二醛、H₂O₂和O₂^-含量极显著增加,而可溶性蛋白含量则相反。遗传分析表明,osyes1受一对隐性核基因控制,利用图位克隆技术将OsYES1基因定位于第7染色体短臂的RM21353与RM21384之间,物理距离为708 kb。【结论】由于osyes1叶片过早黄化衰老导致与产量相关的重要农艺性状显著下降。OsYES1基因定位在第7染色体两个SSR标记(RM21353和RM21384)之间的708 kb的物理区间内。     

Morphology and nutritive value of perennial ryegrass cultivars at different phenological stages

Eight perennial ryegrass cultivars (representing the variations in ploidy, heading date and water‐soluble carbohydrates concentration) were investigated for morphology and nutritive value at three phenological stages: pre‐heading vegetative, reproductive and post‐flowering vegetative stages. Chemical compositions and digestibility of morphological components (lamina, pseudostem and reproductive stem) from each perennial ryegrass cultivar were analysed in a split‐plot design. At the vegetative stages, perennial ryegrass cultivars differed significantly in the proportions of lamina and pseudostem. Tetraploid cultivars, Base and Bealey, always had the greatest lamina proportion (51.8% and 53.2% at the pre‐heading and post‐flowering vegetative stages respectively). At the reproductive stage, the emergence of seed heads diminished the differences in morphology among cultivars. Perennial ryegrass cultivars also had distinct nutritive value throughout three phenological stages. The high‐sugar cultivar, AberMagic, had high WSC concentrations (276, 227 and 90 g/kg DM at the pre‐heading vegetative, reproductive and post‐flowering vegetative stages respectively); the intermediate‐heading cultivars, Kamo and Commando, generally had a lower organic matter digestibility in dry matter than the late‐heading cultivars at the pre‐heading vegetative (70.7% vs. 74.4%) and reproductive stage (63.9% vs. 68.2%). However, although the morphological components were different in nutritive value consistently, the differences in morphology did not account for the variation in nutritive value among perennial ryegrass cultivars.     

Storage and Remobilization of Soluble Carbohydrates after Heading in Different Plant Parts of a Winter Wheat Cultivar

Abstract

Several types of water soluble carbohydrates (WSG) were traced into plant parts of a winter wheat (Triticum aestivum L.) cultivar from heading to physiological maturity. Field grown plants were harvested at intervals of a few days and divided into grain, chaff, leaf blades, leaf sheaths, rachis + peduncle and culm internodes. Leaf blades and sheath showed the peak of WSC contents at about anthesis. Culm internodes accumulated fructan and sucrose during the early grain-filling phase, from a week after anthesis until the milk-ripe stage, then remobilized them during late and final grain filling phases, from the milk-ripe stage until maturity. The amount of sucrose known as short-term storage WSC was higher than fructan known as long-term storage WSC in each internode throughout the grain-filling phase. Chaff showed a large amount of fructan and fructose before anthesis, although it did very little sucrose. A pattern of sucrose accumulation in chaff was very different from that of fructan, unlike the other parts. These patterns of changes in WSC contents in plant organs roughly corresponded with four grain-filling phases, the initial, early, late and final phases.     

Further studies on the effect of phosphate fertilizer and propyzamide on the growth of white clover slot-seeded into permanent pasture

Assessments were made of the clover yield and clover content between early June and late July 1984 of white clover in a permanent pasture which had been slot-seeded in spring 1982.
Past reserves of phosphate or application of propyzamide alone only slightly increased clover dry matter yield but together they increased it from 13 to 785 kg dry matter ha^-1 and gave 31% clover in the total herbage yield. Applications of P₂O₅ during the experiment, alone or together with past reserves of phosphate, Iased clover yield from 13 to 242 kg dry matter ha^-1 and the proportion of clover from 1 to 10%. However, highest yields (1282 kg) and clover content (37%) were attained when P₂O₅ and propyzamide were applied to treatments with past reserves of phosphate.
These results confirmed the trends evident during the second year and also indicated a potential role for grass-suppressants in increasing management options during the early years after slot-seeding.     

The chemical composition and nutritive value of grass silages prepared with no additive or with the application of additives containing either Lactobacillus plantarum or formic acid

A mixture of perennial and hybrid ryegrasses(234 g DM kg^-1) was forage harvested and ensiled after a 24-h wilt in good ensiling conditions in 2-t capacity silos with no additive application (control) or with the application of either Lactobacillus plantarum , 4 × 10⁶ (g fresh weight of grass)^-1, or of 31 formic acid t^-1. Sufficient 2-kg capacity laboratory silos were also filled with grass to monitor the changes in chemical composition of the ensiled grass with time. In laboratory silos, inoculation with L. plantarum resulted in a more rapid fall in silage pH ( p < 0.001) and a more rapid production of lactic acid ( P < 0.001) than in the control silage. At the end of the storage period (laboratory silos, 80 d; 2-t silos, 200-300 d), the inoculated silos had lower pH ( p ammonia-N (g kg N¹) and acetic acid contents ( p < 0.01) and higher water soluble carbohydrate (WSC), lactic acid (P<00.1) and ethanol ( p < 0.05) contents than the control silage. The formic acid-treated silage had significantly lower contents of ammonia-N (g kg N^-1, p < 0.05), acetic and tactic acids (p<0.01) and higher contents of WSC and ethanol ( p < 0.01) than the control silage. When fed to wether sheep, the digestibilities of DM, organic matter and gross energy were not altered by additive treatment. The digestibility of modified acid-detergent fibre was lower for both the inoculated ( P < 0.01) and formic acid-treated silages ( p < 0.05). However, N retention was improved ( p < 0.05) by both additive treatments. Silage intake was improved ( p < 0.01) by additive treatment from 53.4 (control) to 58.0 (inoculated) and 60.4 (formic acid) g DM (kg live weight^0.75)^-1d^-1.     

Changes in stubble carbohydrate content during regrowth of defoliated perennial ryegrass (Lolium perenne L.) on two nitrogen levels

Changes in stubble carbohydrate content during the regrowth of ryegrass ( Lolium perenne L.) grown under hydroponic conditions at two nitrogen levels were studied as a function of time by high-performance liquid chromatography. Experimental data showed that regrowth at a non-limiting nitrogen level (1·0 mol m⁻³ NH₄NO₃) involved two different physiological periods. The first occurred during the first 6 d and was characterized by the mobilization of 60 to 90% of the soluble carbohydrates (i.e. glucose, fructose, sucrose, oligofructans and polyfructans). During the second period (6.28 d of regrowth) carbohydrate contents rose to the values observed prior to cutting (20% of dry matter at the 28th d of regrowth).
The effect of low nitrogen conditions (0·2 mol m⁻³ NH₄NO₃) was observed only during the second phase. Plants regrown in a nitrogen-starved medium accumulated 2·3-fold more polyfructans than plants regrown in a non-limiting nitrogen medium. Their fructose and glucose contents remained at 2% of dry matter from the end of the first phase of mobilization.
The experimental results are interpreted and discussed in terms of the existence of two distinct fructan synthetic pathways.     

The use of roll-conditioning and potassium carbonate (K2CO3) to increase the drying rate of lucerne (Medicago sativa L.)

Mechanical and chemical treatments to accelerate the drying of cut lucerne were evaluated under laboratory conditions. Plant material was treated with a 016 M solution of potassium carbonate (K₂CO₃) and/or lightly pressed between a pair of smooth rollers (roll-conditioning).
Drying times to 33% moisture content (MC), expressed on a dry weight basis (dwb), were reduced by 49% by roll-conditioning, 76% by K₂CO₃) treatment and 77% by the combined K₂CO₃+ roll-conditioning treatment. The main benefit from combining the two forms of treatment was an improved uniformity of drying; when whole shoots were at 61% MC (dwb) the difference between leaf and stem moisture contents was reduced by 28% (roll-conditioning), 38% (K₂CO₃) and 54% (K₂CO₃+ roll-conditioning) relative to the untreated control.     

西瓜品种‘黑皮’对瓜蚜的抗性遗传分析

采用单株蚜量比值法室内鉴定与RAPD、SCAR标记相结合的方法,系统开展了西瓜品种‘黑皮’对瓜蚜的抗性遗传分析。结果表明,以‘黑皮’和‘花绿’为亲本的杂交F₁代对瓜蚜表现为抗性,自交F₂代植株表型出现抗感性分离,抗蚜与感蚜植株分离比经χ²测验符合3∶1分离规律,并用筛选获得的RAPD标记WO4₆₀₀和SCAR标记WO4-S₅₃₀验证了4个抗蚜品种、4个感蚜品种和10个F₂抗蚜单株、10个F₂感蚜植株。结果以‘黑皮’为亲本的西瓜抗蚜性由单显性核基因控制且能稳定遗传,‘黑皮’‘绿美人’‘黑美人’和‘惠兰’品种对瓜蚜具有良好抗性,‘花绿’‘凤光’‘蕙宝’和‘甜美人’品种则易感蚜虫。     

RESEARCH NOTE

Data from twenty-two experiments conducted at tour ADAS Research Centres during 1980–92 were used to compare untreated silages with silages treated with formic acid, with or without added formalin, commercial inoculants or molasses. The sillages were made from herbage whose dry-matter (DM) and water-soluble carbohydrate (WSC) contents were 277 (s.e. 0.46) g DM kg⁻¹ and 36 (s.e. 8.1) g kg⁻¹ respectively. Inoculant use significantly decreased silage pH and ammonia-N, significantly increased lactic acid and total acid content, and decreased butyric acid and total short-chain fatty acids. Formic acid use significantly increased silage lactic acid and total acid content, and decreased butyric acid content, whereas formic acid+formalin significantly decreased silage ammonia-N level. Molasses had little effect upon silage fermentation. Improvements in silage fermentation, however, produced little benefit in terms of either silage DM intake or liveweight gain when the silages were offered to growing lambs.
It is suggested from the results that inoculant- and formic acid-based additives can be used to improve the fermentation of big-bale silages.     

The response of Whitegrass [Cortaderia pilosa (D'Urv.) Hack.] to nitrogen nutrition

To investigate the potential for increasing Falkland Island Whitegrass [ Cortaderia pilosa (D'Urv.) Hack.] pasture production through application of nitrogen (N) fertilizer, two hydroponic experiments were conducted. First, 5 mg l^–1 N was supplied to plants as nitrate (NO₃^–), urea [CO (NH₂)₂], ammonium (NH₄⁺), or a nine parts NH₄⁺: one part NO₃^– mixture. At harvest, plants grown in a NO₃^– medium had about half the biomass of plants grown in a NH₄⁺ medium. In the second experiment plants were supplied with 1, 3, 10, 30 or 100 mg l^–1 NH₄⁺-N. Plants at 1 and 3 mg l^–1 N had the largest biomass of young root and the lowest shoot–root ratios. Leaf extension rate was low in the 1 mg l^–1 N treatment. Plants given 10 mg l^–1 N had the greatest proportion of green shoot material but little root growth; while those at 100 mg l^–1 N produced very little shoot and root biomass. Preferential assimilation of NH₄⁺-N and a low N requirement make Whitegrass well adapted to dominating vegetation on much of the Falkland Islands.     

茶树CsLHTs亚家族基因的克隆与表达分析

氨基酸是茶叶的重要品质成分和氮素贮存形式,因此开展茶树体内氨基酸转运蛋白的研究尤为重要。本研究从茶树转录组中筛选得到5条茶树LHTs(Lysine histidine transporters,赖氨酸/组氨酸转运蛋白)家族基因序列,并从龙井43中成功克隆获得4个茶树LHTs基因,分别命名为CsLHT1、CsLHT6、CsLHT8.1和CsLHT8.2。对该亚家族编码的氨基酸序列的理化性质和功能结构进行预测,结果显示CsLHTs亚家族含有9~11个跨膜区;且含有与氨基酸转运相关的结构域。为了明确在不同茶树品种和氮素水平间CsLHTs基因的表达差异,本研究选用3个茶树品种的扦插苗为试验材料,水培条件下氮饥饿两周后,分别用0.2、2、10mmol·L^-1的NH4NO3进行处理。利用qRT-PCR分析了CsLHTs在不同组织间的表达情况,结果表明4个基因在茶树营养组织中均有表达。经氮素处理后,CsLHTs基因在3个氮素水平和3个品种中呈现出不同的变化规律。CsLHT1、CsLHT6和CsLHT8.2在品种间的表达差异程度高于不同氮素水平间的基因表达差异。CsLHT8.1对氮素处理有明显的响应,尤其经0.2mmol·L^-1和10mmol·L^-1的NH4NO3处理72h后,在氮高效品种中茶302根中呈上调表达,表明CsLHT8.1可能参与氨基酸由根部向地上部的转运过程。     

Assessment of contrasting perennial ryegrasses, with and without white clover, under continuous sheep stocking in the uplands

Comparative sheep production from Aurora (very early-flowering), Meltra (late-flowering tetraploid) and Aberystwyth S23 (late-flowering) perennial ryegrass ( Lolium perenne L.) varieties was assessed as both grass-only (200 kg N ha⁻¹) and grass-white clover ( Trifolium repens L.) (75 kg N ha⁻¹) swards under continuous stocking management. Beulah Speckled Face ewes and their Suffolk cross lambs were used from late April to mid-July. From late July to early November only lambs grazed the pastures.
Mean (1985–87) total annual lamb production per hectare from Aurora and Meltra was 16% and 13% more than that from S23. The magnitude of the differences between these varieties and S23 declined from the first to the third year. Aurora gave 29% more lamb output per hectare than S23 in 1985 but only 10% more in 1987, while the advantage of Meltra over S23 fell from 19% in 1985 to 6% in 1987. Seasonal lamb production per hectare varied between the grasses, especially during spring when lamb output from Aurora was 43% and 22% more than that from S23 and Meltra respectively, with that from the tetraploid being 17% higher than that from S23.
It is concluded that the superior spring output from Aurora offers the farmer the opportunity to reduce his dependence on bought-in feedstuffs, hence improving the efficiency and profitability of lamb production from grassland.     

Opportunities for reducing the environmental impact of dairy farming managements: a systems approach

Dairy farming systems are important sources for the emission of a number of materials that include various forms of nitrogen (NO₃⁻, N₂O and NH₃) with potential environmental impact. The present paper is a systems synthesis study and assesses the likely impact of changes in management on N flows and losses. These include tactical fertilizer adjustment, slurry injection, maize silage production and the use of white clover as an alternative to fertilizer N. Implications for greenhouse gases (N₂O and CH₄) and support energy have also been considered. Substantial reductions in inputs and total and proportional losses by all die options considered were predicted by this study. Thus, using a tactical approach to fertilizer application and injecting slurry or using 50% maize silage reduced overall N losses from 160 (under conventional management) to 86 and 109kg Nha⁻¹ respectively. Combining both possibilities reduced losses further to 69 kg ha⁻¹. Although use of white clover, especially at low contents in the sward, was the most effective regime to reduce losses, this was at some cost to production so that losses per livestock unit (LU) did not always differ from those under other managements. Changing the N management had consequences for greenhouse gas emission with an estimated maximum 70% reduction in N₂O release. The effects on CH₄ emissions were relatively small. Substantial reductions in support energy costs were also obtained: these arose mainly from the reduction in fertilizer N use, which represented 66% of the total support energy in the original system.