Effect of a stay-green locus on the dry-matter yield, nitrogen yield and shoot density of perennial ryegrass

A rare stay‐green allele transferred from meadow fescue (Festuca pratensis L.) to perennial ryegrass (Lolium perenne L.) has improved both the colour of turf and the nutritive value of herbage. In this study its effect on shoot density and forage yield was assessed. Equivalent populations of perennial ryegrass were constructed with and without the stay‐green allele, following eight generations of backcrossing to perennial ryegrass. The stay‐green population, the normal population and the cv. AberStar were compared over two harvest years (2005 and 2006) in a field experiment with six application rates of N fertilizer (100, 200, 300, 400, 500 and 600 kg ha^?1 annually). There were no significant interactions between level of N fertilizer and population in any of the traits measured. The mean annual dry‐matter (DM) yield over all populations and fertilizer levels was 6·45 t ha^?1 lower in the second harvest year. Mean annual DM yields over all fertilizer levels of the normal population were higher than, or equal to, AberStar while those of the stay‐green population were significantly (proportionately 0·10–0·13) lower than the normal population. In 2005, the mean total yield of N in the herbage of the stay‐green population was 0·09 lower than that of the normal population and the mean concentration of N over all harvests was 1·5 g kg^?1 DM higher. The shoot density of the stay‐green population after the last harvest in November 2006 was 0·18 lower than that of the normal population (3689 and 4478 shoots m^?2 respectively).     

Agronomic factors affecting the yield and quality of forage maize in Ireland: effect of sowing date and plastic film treatment

The objectives of these studies were to examine the effects of sowing date and plastic film on the yield and quality of forage maize ( Zea mays L.) in Ireland, a marginal maize-growing area. In 1989–95, comparisons were made of maize sown through clear plastic film (PP treatment), and maize sown in the conventional manner without plastic (NP treatment), in terms of dry-matter (DM) yield and quality (cob, grain and starch contents). The PP treatment significantly increased DM yields in five years, with a mean yield increase of 3·10 t ha⁻¹. Whole-plant DM content increased (significant in four years) by a mean of 0·15; cob content increased (significant in five years) by a mean of 0·32; grain content increased (significant in all of the three years examined) by 0·75; and starch content increased from 236 to 318 g kg⁻¹ DM ( P  < 0·01) in 1995 where the plastic film treatment was used. Organic matter digestibility values were similar for both treatments in 1995. Sowing date in the April-May period had no consistent effect on DM yields, but early sowings did increase cob (significant, except in 1994), grain (significant in one (1995) of the two years tested) and starch ( P  < 0·05) contents (only tested in 1995). Sowing on 11 April 1995 through perforated plastic gave lower yields than the NP treatment sown on the same date, due to severe frost damage in early May.     

The effects of a foliar spray containing phosphorus and zinc on the development, composition and yield of forage maize

Forage maize grown in areas where spring temperatures are low and accumulated heat is limited will be restricted in terms of maturity and thus nutritional value. A stagnant growth phase is commonly caused by low temperatures between germination and the five-leaf stage, which could be caused by reduced mineral availability. The effects on maize plant development and harvest characteristics of supplying phosphorus and zinc to young plants in a foliar spray were investigated. Three different application dates, between the four-leaf and the seven-leaf stage, were compared. Applying the phosphorus and zinc foliar spray at the four-leaf stage resulted in a significant ( P  < 0·05) increase in starch content at harvest. Cob index [proportion of plant dry matter (DM) in the cob] was increased ( P  < 0·05) by applying the nutrient spray at the four-, five- and seven-leaf stages. However, there was no effect on DM yield, suggesting some alteration in partitioning within the plant.     

Agronomic factors affecting the yield and quality of forage maize in Ireland: effect of plastic film system and seeding rate

The objectives were to compare the effects of two plastic film systems [perforated (PP) and complete‐cover (CC) systems] on the yield and quality of forage maize, and to study the effects of seeding rate on maize grown with, and without, plastic film. Between 1995 and 1998 (Experiments 1 and 2), comparisons were made of maize without plastic film systems (NP), sown through clear plastic film (PP) and covered with clear plastic film (CC). In the CC system, the plastic was removed manually from the crop. Two dates of removal (CC1 and CC2) were compared in 1995, while four removal dates (CC1, CC2, CC3 and CC4) were examined in 1996–98. In 1996–98, three sowing dates (early, mid‐April; mid, early‐May; late, mid‐May) were also examined. Four seeding rates (78 200, 93 900, 107 000 and 126 000 seeds ha^?1) were examined in two experiments (Experiment 3 in 1996 and Experiment 4 in 1996–98). No plastic was used in Experiment 3, while three plastic treatments (NP, PP and CC) were examined in Experiment 4. In the CC treatment, the plastic film was removed at the six‐ to eight‐leaf stage. In Experiment 1, the PP treatment gave lower DM yields than the NP treatment due to frost damage which killed 0·30 of the plants in the PP treatment. Plants were undamaged by frost in both CC treatments, and the CC2 treatment (plastic removal at the six‐leaf stage) gave significant increases in DM and grain yields. In Experiment 2, averaged over years and sowing dates, DM yields were significantly increased by all plastic film treatments except CC4. All plastic film treatments gave significantly earlier tassel emergence than the NP treatment, and significantly increased grain yields and contents of DM and grain. The highest yields of DM and grain were obtained from the PP system. Within the CC treatments, leaving the plastic film intact until the ten‐leaf stage (CC4) gave lower yields of DM and grain than removing the plastic film at an earlier stage. Averaged over years, the largest DM yields were obtained from the CC system with early‐sown material, while the yield differences between treatments with late‐sown crops under this system were not significant. Highest DM and grain yields were obtained with early sowing, while late sowing gave lower contents of DM and grain, and later tassel emergence. In Experiments 3 and 4, DM and grain yields increased as seeding rate increased up to 126 000 seeds ha^?1 with NP and CC plastic treatments. With the PP treatment, DM yield reached a plateau at 107 000 seeds ha^?1. Seeding rate did not significantly affect DM content in either experiments but grain content declined in both experiments as seeding rate increased.     

Variation in forage yield and quality of three cruciferous catch crops grown in southern England

Cruciferous catch crops are an important source of forage, particularly in sheep systems, but due to their late sowing date, commonly July or early August, soil moisture is often a limiting factor in crop establishment and subsequent growth, causing wide variations in yield from year to year. Crops of stubble turnip ( Brassica campestris ssp. rapifera ), forage rape ( B. napus ssp. biennis ) and fodder radish ( Raphanus sativus ) were grown at Hurley between 1969 and 1977. Fodder radish was the most variable in dry matter (DM) yield, while stubble turnip was the most stable. Both DM yields and in vitro digestibilities rose during the autumn, reaching a maximum in mid-December for stubble turnip and forage rape, and in mid to late November for fodder radish. Yield and digestibility subsequently declined. The N concentrations of the forages exhibited a contrary trend, reaching minimum values at about the time of the highest DM yields. The gradual changes in crop quality suggest that the crops are well suited to grazing utilization, in which management is simplified if crop quality shows little variation.     

磷对大豆不同品种产量和品质的影响

土壤盆栽试验表明,低磷处理下大豆品种的籽粒产量很低,籽粒中蛋白质含量高,脂肪含量低。施磷后大豆的产量极显著增加,但增产效果品种间差异也极显著。施磷大大降低籽粒中蛋白质和氨基酸含量,而增加脂肪含量;对脂肪酸组成中的油酸和亚油酸含量也有影响。     

Yield and quality of forage maize grown under marginal climatic conditions in Northern Ireland

The expansion of maize (Zea mays) into cooler areas has been facilitated by the availability of early maturing cultivars and by cultivation under plastic mulch. However, year‐to‐year variation in harvest quality remains a problem. The yield and quality of ‘Goldcob’, an early maturing forage maize, were assessed over 5 years from plots grown in the open and under plastic mulch. For both treatments, there was significant between‐year variation in yield and quality (starch content, metabolizable energy, organic matter and D‐value), and starch content was particularly variable. The use of plastic mulch to warm the soil advanced the establishment of the crop, with silking occurring on average 19 days earlier. This resulted in significantly higher yields under plastic mulch, with a mean increase of 3·9 t ha^?1. The plastic mulch also resulted in significant increases in quality parameters, with starch content showing a mean increase of 36%. The Ontario heat unit model explained much of the variability in yield, both in the open and under plastic mulch. Plastic mulch had no consistent effect on Ontario heat units accumulated prior to silking, but Ontario heat units accumulated between silking and harvest (OHU_post‐silk) were found to be an adequate predictor of yield. The response of starch content was more complex, showing a clear plateau in the response to temperature at 1200 OHU_post‐silk, above which the accumulation of starch appears limited by other factors.     

Effects of early planting and cultivars on the yield and agronomic traits of soybeans grown in southwestern Japan

Early planting contributed to increased soybean yields in the U.S. Because a double-cropping system dominates in southwestern Japan, early planting is not performed; it is thus unclear how much the yield potential could be increased by early planting. To address this question, we planted seven U.S. and five Japanese cultivars on around 20 May (early planting), measured the agronomic traits, including yield, yield components, and oil and protein contents, and compared these traits with those of the same cultivars planted on around 20 July (normal planting). In the early planting, the yields of the U.S. cultivars were 322–453 g m^?2, whereas the highest yield among the Japanese cultivars was only 315 g m^?2, which is significantly lower than those of the top five U.S. cultivars, indicating the adaptability of U.S. cultivars to early planting. The increases in yield obtained with early planting were 99–199 g m^?2 and ?26–144 g m^?2 for the U.S. and Japanese cultivars, respectively. The yield obtained by early planting was positively correlated with the pods m^?2, seeds pod^?1, and oil contents, but negatively correlated with the sterile pod rate, 100 seed weight and protein content. In the early planting, the U.S. cultivars had greater pods m^?2, seeds pod^?1 and oil content and less sterile pod rate, 100-seed weight, and protein content than the Japanese cultivars. These results suggest that early planting can increase the yield in southwestern Japan, if cultivars with agronomic traits observed in the U.S. cultivars of this study are grown.     

Nutritive quality and energy yield of high oil,opaque-2 and waxy maize hybrids compared to normal maize hybrids

Grain yield, chemical composition, protein quality and digestible energy were measured for 18 maize varieties (opaque-2, high oil, waxy hybrids, normal hybrids) cultivated in Yugoslavia. Protein quality assessment was based on amino acid composition, and true protein digestibility, biological value, net protein utilization and utilizable protein as determined in nitrogen balance experiments with rats. The protein concentration in dry matter varied from 8.63–18.81% while the fat concentration varied from 4.45–16.13%. There were only minor differences in ash and crude fibre, while starch and sugar varied inversely to fat and protein concentration. Lysine levels were approximately 30% higher for the opaque-2 varieties compared with normal maize, while leucine levels were about 30% lower. Yields were extremely high for all varieties with the highest value being 10.3 tonnes/ha. Due to the high yields, protein production/ha was high in range of 822–977 kg. This resulted in high yields of amino acids/ha. Protein utilization was very high in the opaque-2 varieties, which had the highest lysine contents. The biological values were close to 80 in these varieties, whereas they were only 60–65 in the normal maize varieties.     

Impact of increasing shade levels on the dry-matter yield and botanical composition of multispecies forage stands

Botanical diversity has been linked to increased biomass production of grasslands, but these relationships have not been explored as extensively in silvopasture systems where shade impacts on forage mass are variable due to the unique structure and environment of each system. The objective of this study was to evaluate the impact of multiple artificial shade levels on the DM yield and botanical composition of three cool-season forage mixtures near Blackstone, Virginia, USA. Mixtures were as follows: simple = tall fescue [Schedonorus arundinaceus (Schreb.) Dumort., nom. cons.] and white clover (Trifulium repens L.); intermediate = simple + orchardgrass (Dactylis glomerate L.) and red clover (Trifolium pretense L.); and complex = intermediate + Kentucky bluegrass (Poa pratensis L.), birdsfoot trefoil (Lotus corniculatus L.) and alfalfa (Medicago sativa L.). Slatted structures created conditions of 30%, 50% and 70% shade relative to a full sun control. Forages were harvested mechanically (no grazers present). Annual yield (DM kg/ha) did not differ among mixtures. As compared to full sun, annual yield was no different at 30% shade, but was reduced by 22 and 36% at 50 and 70% shade respectively. In contrast to other species in the mixtures, orchardgrass increased in proportion when grown beneath all shade levels and is recommended for silvopasture use. Orchardgrass is not particularly well-adapted to the transition zone between the northern temperate and southern subtropical United States; therefore, these results indicate that silvopastures may be an effective way to integrate marginally adapted, shade-tolerant cool-season forages into transition zone grazing systems.     

Effect of maturity stage at harvest on the ensilability of maize hybrids in the early and late FAO classes,grown in areas differing in yield potential

The aim of this study was to assess the effects of earliness (according to FAO class), maturity stage at harvest and environmental conditions on the ensilability of maize hybrids described by their fermentation products and by a fermentation quality index (FQI). Maize hybrids belonging to early (n = 14) and late (n = 15) FAO classes were grown in low, medium and high potential yield areas and harvested at an early (EH), medium (MH) and late maturity stage (LH), that is, at 1/3, 2/3 and 5 d after the 2/3 milk line stage, respectively, according to a split‐plot design. Upon harvest, each sample (n = 522) was analysed for dry matter (DM) and water‐soluble carbohydrates (WSC) before being ensiled in vacuum‐packed bags (n = 1,044). After 60 days of conservation, samples were analysed for DM and fermentation products. In the pre‐ensiling phase, DM was higher in early hybrids (p = .001), low yield areas (p < .001) and at LH maturity (p < .001), whereas WSC contents were higher in early hybrids (p < .001), medium yield areas (p < .001) and at EH maturity (p < .001). With regard to silages, early hybrids had a higher FQI (p < .001), which was highest in areas with a high yield potential (p < .01) and at EH maturity (p < .01). Late hybrids proved to be better suited for low yield areas compared with early hybrids (p < .01) and had a higher FQI at EH and MH than at LH maturity (p < .01).     

Rates and timing of nitrogen fertilizer application on yield,nutritive value and nutrient‐use efficiency of early‐ and late‐sown forage maize

The outcomes of previous studies have resulted in differing recommendations on the rate and timing of fertilizer N applications for forage maize. In order to gain an improved understanding of the role of N fertilizer, a field experiment was carried out to investigate the effects of time and rate of N application on total and plant‐fraction yield, nutritive value and efficiency of nutrient utilization in early‐ and late‐sown forage maize. Treatments included two sowing dates (early, late), two rates of N (0, 135 kg ha^?1) applied pre‐sowing (N1) and three rates of N (0, 79, 158 kg ha^?1) applied post‐sowing (N2) at the six‐leaf stage (V6). Application of N at N1 (N0 vs. N135) increased dry‐matter (DM) stover yield by 11% and total yield by 7%. Application of fertilizer N at N2 (N0 vs. N158) increased grain yield by 44% and total yield by 34%. Application of N2 also increased irrigation and total water‐use efficiency (WUE) from 30 to 40 and 46 to 61 kg DM ml ^?1 water respectively. Late sowing increased DM yield by 6%, but decreased WUE compared with early sowing. The results indicate that application of N at both N1 and N2 is essential to maximize total DM yield from forage maize, but application at V6 is recommended when N input is reduced.     

播期对饲用油菜鲜草产量和品质的调控研究

为确定华北平原饲用油菜高产优质的适宜播期,选用甘蓝型油菜品种4个,设置4个播期,研究不同播期下温度对饲用油菜鲜草产量和饲用品质的调控效应。结果表明,随播期推迟,饲用油菜生育期内日均温与有效积温升高,花前生育期天数缩短但花后生育期延长,总生育期天数缩短2～7 d。饲用油菜鲜草产量随播期推迟呈降低趋势,3月28日前播种超过35 t/hm2;品种间华油杂62鲜草产量显著高于其它品种（P<0.01）。饲用油菜鲜草产量和饲用品质与纤维含量显著负相关,中性洗涤纤维含量与苗期的有效积温量极显著负相关,与营养生长和花后有效积温量显著正相关。因此,在华北平原春播饲用油菜可选用华油杂62,播期以3月8日-3月18日为最佳,鲜草产量稳定在50 t/hm2以上,具有较高的粗蛋白、淀粉、水溶性碳水化合物和总可消化养分含量,可实现华北平原饲用油菜的高产优质生产。     

Influence of competition,irrigation levels and nitrogen fertilization on protein content and protein yield of three spring wheat (Triticum aestivum L.) cultivars

Protein content and protein yield of three spring wheat cultivars differing in morphological and physiological growth characters were found to be influenced by intercultivar competition, irrigation levels and nitrogen fertilization. The protein content of the tall cultivar C 306 and the protein yield of the dwarf cultivar HD 2160 were more than the other cultivars. Binary mixed stands were not superior to the better component cultivar. Intercultivar competition increased the protein content of dwarf and semi-dwarf cultivars, but decreased the protein content of tall cultivar. On the other hand, protein yield of the dwarf cultivar decreased and that of tall cultivar increased when grown in mixed stands. Protein yield of semi-dwarf cultivar increased when grown with dwarf cultivar, but decreased when grown with tall cultivar. Two or three irrigations increased the protein content and protein yield of all the three cultivars and their mixed stands over one irrigation. Protein content and protein yield of the cultivars and their mixed stands were higher when 150 kg N/ha was applied than when 80 kg N/ha was applied.     

Residual fertilizer effects on dry-matter yield and nutritive value of Mediterranean pastures

Five pastures in an Mediterranean environment in southern Italy were fertilized for 6 years (1993–1998) with nitrogen (N) fertilizer, phosphorus (P) fertilizer and two levels low (L) and high (H) of combined nitrogen and phosphorus fertilizer (N‐P), and compared with a no‐fertilizer control treatment, and the effects on soil variables, dry matter (DM) yield of herbage and floristic composition of the pastures measured. From 1998–2002, half of each plot was fertilized with the same treatments (continued treatment) while the other half received no fertilizer (discontinued treatment). In the year 2001–2002, the plots on the discontinued fertilizer treatments and the plots on the control treatment were used to evaluate the residual effects of the fertilizer treatments. The P and N‐P fertilizer continued and discontinued treatments, in comparison to the control treatment, had a higher content of available P₂O₅ in the soil while under the N fertilizer treatment it decreased. The N and P fertilizer treatments and the residual effects of these treatments led to higher DM yields and proportions of Gramineae and Leguminosae, respectively, compared to the control treatment. Furthermore, differences in the nutritive value of the herbage and floristic composition were observed between the N‐P fertilizer treatments and the control treatment. The residual effect of the N, P and N‐P fertilizer treatments increased DM yield proportionately by 0.063, 0.385 and 0.404, respectively, and reduced the crude protein content of the herbage. The residual effects of the fertilizer treatments on milk forage units (MFU) were 261 for N, 1107 for P and 1003 MFU ha^?1 for N–P fertilizer treatments. Among fertilizers, the residual effect of the N‐P fertilizer treatment promoted an increase in DM yield but produced little variation in floristic composition of the pasture. In general, the fertilizer treatments increased DM yield and nutritive value of herbage and reduced floristic composition in pastures on these Mediterranean sites.     

不同生态条件下大麦品种的适应性研究

通过对引自黑龙江、四川和河南等地的13份大麦品种材料进行试种,观察这些大麦在黔中地区自然生态条件下和盆栽条件下的生长发育特性和农艺性状表现。结果显示,所有参试品种材料都能完成生长发育的各个阶段,在大麦物候期和主要农艺性状上,不同品种材料间存在着明显的差异,方差分析均达极显著水平(p<0.000 1)。在供试大麦的产量构成上,13份材料中其千粒重超过50 g的有一半以上,仅3份材料的千粒重不足45 g。同时,播期、栽培方式和环境条件等对引种大麦生长的影响极显著,物候期与农艺性状以及农艺性状间存在显著斯皮尔曼秩相关性。综合分析表明,在黔中生态气候条件下,13份省外大麦品种材料均能正常生长,且具有良好的生态适应性,从而为进一步筛选出综合性状优良的大麦品种,培育能适应在贵州种植的大麦新品种提供依据。     

The effect of accumulation period and harvest date in spring on dry-matter yield and forage quality in mixed swards containing Lolium spp. and Trifolium subterraneum in Western Australia

The object of this study was to determine the effect of closing date and date of harvest for conservation (accumulation period), on dry‐matter (DM) yield and forage quality of annual pasture in Western Australia. The field study comprised 48 plots, 2 m × 2 m, sown with either annual ryegrass (Lolium rigidum Gaud.) or Italian ryegrass (L. multiflorum Lam.), and mixed with subterranean clover (Trifolium subterraneum L.). Defoliation of swards until the end of winter was at the three leaves tiller^–1 stage. In spring, once stem nodal development had commenced, swards were defoliated every 3–4 weeks. Swards were defoliated either twice with three leaves tiller^–1 (accumulation period 1 commenced on 15 August); twice with three leaves tiller^–1 and then once after 4 weeks (accumulation period 2 commenced on 11 September); twice with three leaves tiller^–1 and then twice after 4‐week intervals (accumulation period 3 commenced on 9 October) or; twice with 3 leaves tiller^–1 and then twice after 4‐week intervals and then once after 3 weeks (accumulation period 4 commenced on 30 October). From the commencement of the accumulation period, tiller density, DM yield and forage quality were determined weekly for up to 10 weeks. There was a positive quadratic association between DM yield and days after the commencement of the accumulation period. Yields were maximized from accumulation period 1 with 5·3, 6·6 and 9·5 t DM ha^–1, and growth rates were 140, 128 and 145 kg DM ha^–1 d^–1, for Wimmera annual ryegrass and Richmond and Concord cultivars of Italian ryegrass respectively. In contrast, in vitro dry‐matter digestibility (IVDMD) and crude protein (CP) content were negatively associated with days after the commencement of the accumulation period, and initial values were greater than 0·80 and 180 g kg DM^–1 for IVDMD and CP content respectively. The rate of decline in IVDMD d^–1 for Wimmera annual ryegrass was 0·005, 0·019 and 0·012 d^–1 for accumulation periods 1, 2 and 3, respectively, while for Italian ryegrass cultivars Richmond was 0·015, 0·011, 0·02 and 0·012 d^–1 and Concord was 0·014, 0·009, 0·013 and 0·01 d^–1, for the 4 accumulation periods respectively. It is recommended that annual and Italian ryegrass pastures be harvested between 10% and 20% inflorescence emergence when IVDMD will exceed 0·70 regardless of cultivar and/or defoliation practice prior to the commencement of the accumulation period.     

Effect of replacing time available for grazing with time available for eating maize silage and soyabean meal on milk yield and feeding behaviour in dairy cows

Low rates of herbage dry matter (DM) intake impose limits on total daily DM intake in grazing dairy cows. The objective of this study was to increase total daily DM intake and milk production by restricting daily time available for grazing (TAG) and replacing it with time available for eating a maize silage/soyabean meal (TAMS) diet indoors. The treatments (TAG + TAMS) were 20 + 0, 19 + 1, 10 + 10 and 5 + 15 h. Measurements were made of milk production, intake and feeding behaviour. The interactions of TAG + TAMS treatments with sward height (SH) and concentrate level (CL) were also examined. Two experiments, each lasting 42 days, were carried out in spring ( Experiment 1 ) and autumn ( Experiment 2 ) using forty‐eight and twenty‐four Holstein‐Friesian cows respectively. Treatments were arranged in a factorial design with TAG + TAMS treatments, SH ( Experiment 1 only) and CL as the independent variables and a TAG + TAMS of 20 h. Reducing TAG and increasing TAMS significantly reduced estimated herbage DM intake and significantly increased maize silage/soyabean meal intake in both experiments, but there were no significant main effects of TAG + TAMS treatments on milk yield (mean, 27·4 and 25·5 kg d^?1 for Experiments 1 and 2 respectively), and yield of milk constituents. Increasing SH ( Experiment 1 ) and CL ( Experiments 1 and 2 ) significantly increased milk yield. In Experiment 1 , there was a significant interaction between TAG + TAMS treatments and SH with the taller sward height of 8–10 cm and the 20 + 0 treatment having the highest milk yield (29·7 kg d^?1) and the 5 + 15 treatment the lowest (27·2 kg d^?1), whereas at the lower sward height of 4–6 cm, milk yield was lowest on the 20 + 0 treatment (25·5 kg d^?1) with the other three treatments being higher (mean, 26·9 kg d^?1). Replacing TAG with TAMS significantly increased liveweight gain in Experiment 1 but not in Experiment 2 . Estimated rates of intake of herbage were lower in the autumn experiment ( Experiment 2 , 9·6 g DM min ^?1) than in the spring experiment ( Experiment 1 , 29·4 g DM min ^?1) but rates of intake of maize silage were higher in the autumn (112·4 g DM min^?1) than in the spring (72·5 g DM min^?1). In conclusion, in spring the response to replacing TAG with TAMS was dependent on sward conditions with the highest milk fat plus protein yield being on the 20 + 0 treatment at the high sward height and on the 19 + 1 treatment at the low sward height. The high liveweight gain of the 5 + 15 treatment could be an important means of restoring body condition in grazing lactating cows. In autumn, intakes of herbage were low in spite of its high estimated nutritive value with all treatments having a similar level of performance.     

Effect of tolerance to Septoria tritici blotch on grain yield,yield components and grain quality in Argentinean wheat cultivars

Septoria tritici blotch (STB) caused by Zymoseptoria tritici (Mycosphaerella graminicola) is a major disease of wheat worldwide due to significant losses in grain yield and quality. Disease tolerance is the ability to maintain yield performance in the presence of disease symptoms. Therefore, it could be a useful tool in the management of the disease. Although it is known, that there is disease tolerance to STB in some wheat cultivars, this aspect has not been studied among Argentinean cultivars. The aims of this study were to evaluate genotypic differences in tolerance to STB among Argentinean cultivars, considering the relationship between the area under disease progress curve or the green leaf area or the non-green leaf area duration with the grain yield. In addition the effect of the disease on yield, yield components, test weight, grain protein concentration, wet and dry gluten concentration and the influence of tolerance on these traits was investigated. Field experiments were carried out with ten cultivars in a split-split-plot design during 2010 and 2011. Inoculation treatments were the main plots and cultivars, the subplots. STB significantly reduced grain yield, their components, test weight and increase grain protein and gluten concentration. Cultivar Baguette 10 showed major tolerance to STB, indicated by a consistent low regression slope between the green area duration and yield, while Klein Chaja was non-tolerant due to a high regression slope. However, many cultivars such as Buck Brasil, Buck 75 Aniversario, Klein Escorpion and Klein Flecha had considerably similar regression slopes to Baguette 10, provided good levels of tolerance. Other cultivars presented no significant differences. The correlation coefficient between tolerance and grain yield potential was not significant, suggesting that tolerant high-yielding cultivars can be obtained. No relationship was found between quality group or tolerance with the increase in protein and gluten concentration due to STB either.     

Effects of plastic mulch, sowing date and cultivar on the yield and maturity of forage maize grown under marginal climatic conditions in Northern Ireland

The effects of growing forage maize (Zea mays) with or without plastic mulching treatments on the dry‐matter (DM) yield, cob yield, DM content and starch content was investigated in Northern Ireland in 1996 and 1997. Cultivars differing in maturity characteristics were sown in spring at a range of dates in three replicated plot experiments and were used to compare the effects of two plastic mulches and an untreated control: one plastic mulch completely covered the rows (floating); the other had holes punched in the plastic, through which the plants grew (punch). Between April and October in 1996 and 1997, the Ontario heat units (OU) received were above average at 2489 and 2660 respectively; in those years without plastic mulches, the earliest maturing cultivar, Melody, yielded 11·0 and 13·6 t DM ha^–1, with dry‐matter contents of 214 and 215 g kg^–1 respectively. Mean daily increases in soil and air temperature under plastic mulches of up to 6°C and 11°C, respectively, were closely related to solar radiation. Under plastic mulches, 15% fewer OU were required to reach silking, and 33% more OU were available between silking and harvest. Meaned over three experiments, two years and three cultivars, plastic mulches, when compared with the unmulched control, increased maize yield from 12·0 to 14·7 t DM ha^–1, cob yield from 3·7 to 6·8 t DM ha^–1, dry‐matter content from 230 to 270 g kg^–1 and starch content from 198 to 272 g kg^–1. The effect of plastic mulch on the maturation of the crop was greatest at earlier sowings. In 1997, plants from an early sowing date (10 April) that had recently emerged through the punch plastic mulch were damaged by frost, whereas those in the floating plastic mulch plots were unaffected. When the floating plastic mulch was left on after the six‐ to eight‐leaf stage of the first‐early maize cultivar Hudson, the plants were physically damaged and the yield reduced, but DM and starch contents continued to increase. The increases in yield and dry‐matter content under the plastic mulch were greater in Diamant (second‐early cultivar) than in Melody (first‐early cultivar). It was concluded that, under marginal climatic conditions, plastic mulches ought to be used to improve the reliability of early cultivars rather than growing later maturing cultivars.