The Impact of Underseeding Barley (Hordeum vulgare L.) on Timothy (Phleum pratense L.)-Clover (Trifolium pratense L.; Trifolium hybridum L.) Forage Production in a Cool Maritime Climate

Growing barley (Hordeum vulgare L.) in the year of forage establishment is a common agronomic practice in marginal growing regions, but is often not recommended to growers. We examined the effect of silage barley production over an establishing timothy (Phleum pratense L.)‐clover (Trifolium pratense L.; Trifolium hybridum L.) forage sward in a 4‐year study near St. John's, Newfoundland, Canada. The experiment compared two barley varieties differing in plant height (semidwarf Chapais and Leger), three barley seeding rates and the effect of a forage understorey on forage (barley) production in the establishment year and forage (timothy‐clover) production in the subsequent year. The taller Leger yielded similar forage biomass to Chapais in the year of forage establishment, which (when planted at 375 plants m^?2) was roughly twice that of a pure‐stand timothy‐clover mix. Increasing the barley seeding rate from 125 to 375 plants m^?2 resulted in a linear increase in forage yield in the year of planting. The production of barley forage in the establishment year resulted in reduced timothy‐clover forage yield in the year following barley planted at 125 and 375 seeds m^?2, but not for barley planted at 250 seeds m^?2. Companion planting also altered forage species composition in that higher barley seeding rates resulted in 12–18 % less timothy and 2–4 % lower fibre levels in the year following planting. Barley seeded at rates of 250–375 seeds m^?2 and undersown with a timothy‐clover mixture (harvested at mid‐milk) resulted in greater forage yield of poorer quality than pure‐stand timothy‐clover in the planting year, and a barley seeding rate of 250 seeds m^?2 did not impede forage production in the subsequent year.     

The Influence of Row Spacing and Seeding Rate on Seed Yield and Yield Components of Forage Turnip (Brassica rapa L.)

The effects of four row spacings (17.5, 35.0, 52.5 and 70.0 cm) and five seeding rates (50, 100, 200, 400 and 800 viable seeds m^?2) on seed yield and some yield components of forage turnip (Brassica rapa L.) were evaluated under rainfed conditions in Bursa, Turkey in the 1998–1999 and 1999–2000 growing seasons. Plant height, stem diameter, pods/terminal raceme, total pods/plant, seeds/pod and primary branches/plant were measured individually. The number of plants per unit area was counted and the lodging rate of the plots was scored. The seed yield and 1000‐seed weight were also determined. Row spacing and seeding rate significantly affected most yield components measured. The number of plants per unit area increased with increasing seeding rate and decreasing row spacing. Plant height was not greatly influenced by row spacing and seeding rate, but higher seeding rates reduced the number of primary branches and the stem diameter. The number of pods/main stem was affected by row spacing and but not by the seeding rate. Also, the number of seeds per pod was not affected by either the row spacing or the seeding rate. In contrast, the number of pods per plant clearly increased with increasing row spacing, but decreased with increasing seeding rate. The plots seeded at narrow row spacings and at high seeding rates were more sensitive to lodging. Seeding rate had no significant effect on seed yield in both years. Seed yield was similar at all seeding rates, averaging 1151 kg ha^?1. However, row spacing was associated with seed yield. The highest seed yield (1409 kg ha^?1) was obtained for the 35.0‐cm row spacing and 200 seeds m^?2 seeding rate combination without serious lodging problems.     

Effect of spring fertilization on ecosystem services of organic wheat and clover relay intercrops

Nitrogen (N) deficiency and weed infestation are main factors limiting yield and yield stability in organic wheat. Organic fertilizers may be used to improve crop performance but off-farm input costs tend to limit profitability. Instead, forage legumes may be inserted into the crop rotation to improve the N balance and to control weed infestation. In opposition to simultaneous cropping, relay intercropping of legumes in organic winter wheat limits resource competition for the legume cover crop, without decreasing the performance of the associated wheat.The aim of this study is to evaluate the effect of spring organic fertilization on the performance of intercropped legumes and wheat, and on services provided by the legume cover.Two species of forage legumes (Trifolium pratense L. and Trifolium repens L.) were undersown in winter wheat (Triticum aestivum L. cv Lona) in five organic fields during two consecutive crop seasons. Organic fertilizer was composed of feather meal and applied on wheat at legume sowing. The cover crop was maintained after the wheat harvest and destroyed just before sowing maize.Spring organic nitrogen fertilization increased wheat biomass (+35%), nitrogen (+49%), grain yield (+40%) and protein content (+7%) whatever the intercropping treatment. At wheat harvest, red clover biomass was significantly higher than white clover one (1.4 vs. 0.7 t ha⁻¹). Nitrogen fertilization decreased forage legume above-ground biomass at wheat harvest, at approximately 0.5 t ha⁻¹ whatever the specie. No significant difference in forage legume biomass production was observed at cover killing. Nitrogen accumulation in legume above-ground tissues was significantly higher for white clover than for red clover. Both red and white clover species significantly decreased weed infestation at this date. Nitrogen fertilization significantly increased weed biomass whatever the intercropping treatment and decreased nitrogen accumulation in both clover species (−12%).We demonstrated that nitrogen fertilization increased yield of wheat intercropped with forage legume while the performance of legumes was decreased. Legume growth was modified by spring fertilization whatever the species.     

氮磷配施对西藏河谷农区燕麦与箭筈豌豆混播产量及品质的影响

在海拔4 300m的西藏河谷农区,进行了N、P配合施肥对混播燕麦与箭筈豌豆产量及品质影响的研究。结果表明：刈割期为燕麦乳熟期/箭筈豌豆结荚期,混合饲草产量最高,饲草粗蛋白、粗脂肪含量较高,而酸性洗涤纤维（ADF）与中性洗涤纤维（NDF）较低。N、P及其互作对混播燕麦与箭筈豌豆株高、产量、养分含量的影响显著;在相同施P水平下,随着N的增加,干草产量、株高和粗蛋白呈现先增后减的变化趋势;粗脂肪、ADF和NDF含量随氮肥施用量的增加有不同程度的降低;在相同施N水平下,随磷肥施用量的增加,粗蛋白、粗脂肪、ADF呈增加的趋势,而NDF逐渐降低。施用氮（纯N）140kg/hm ²、磷（P₂O₅）60kg/hm ²处理组合干草产量最高为16 636kg/hm ²,比不施肥对照组增产60.47%;蛋白质含量最高达18.42%。说明N、P施用量分别为140kg/hm ²、60kg/hm ²可作为该地区燕麦与箭筈豌豆混播种植的推荐施肥量。     

Hybrid and N Fertilization Affect Corn Silage Yield and Quality

We determined the effect of N fertilization on dry matter (DM) yield, predicted milk yield, and forage quality of fresh (green chopped) and ensiled forage of two brown midrib (BMR) hybrids, a leafy hybrid, and a conventional silage hybrid. Increasing N rates from 0 to 200 kg ha^?1 increased corn grain, stover and whole plant DM yield and milk yield. The forage yield and quality response to N was similar for all hybrids. Nitrogen fertilization increased forage crude protein (CP) concentration but had little effect on other forage quality components. BMR hybrids, F377 and F657, had the lowest grain, stover and whole plant yield but had the highest digestibility and predicted milk yield Mg^?1 of forage. Predicted milk yield ha^?1 was similar for the BMR, leafy and conventional hybrids. Ensiling reduced starch concentration compared with green chopped forage, but effects on other forage quality variables were less consistent. Hybrid and N fertilization affects were similar for green chopped and ensiled corn forage.     

不同施肥量和施肥方式对苎麻产量和饲用品质的影响

为了研究不同施肥量和不同施肥方式对饲用苎麻(Boehmeria nivea L.Gaud)产量和饲用品质的影响,采用2种复合肥施肥方式与2种尿素追肥方式,结合复合肥和尿素的不同施肥量,共设置8个施肥处理。结果表明:农艺性状方面,表现最好的为复合肥一次性基施(0.054 kg/m2)与尿素每收割一次追肥一次(0.006 kg/m2),其分株数42.00株/蔸、叶茎比2.04、干鲜比0.15;饲用产量方面,表现最好的是复合肥一次性基施(0.108 kg/m2)与尿素每收割一次追肥一次(0.0135 kg/m2),其产量鲜重达17.07 kg/m2,明显优于其他处理;饲用品质方面,复合肥一次性基施(0.108 kg/m2)与尿素每收割一次追肥一次(0.0135 kg/m2)、复合肥分2次施(0.054 kg/m2)与尿素每收割一次追肥一次(0.0135 kg/m2)、复合肥一次性基施(0.054 kg/m2)与尿素每收割一次追肥一次(0.006 kg/m2)3个处理的粗蛋白含量显著优于其他处理。本研究为提高饲用苎麻栽培管理技术提供了参考。     

The Effect of Seeding Rate and Nitrogen Fertilization on Barley Yield and Yield Components in a Cool Maritime Climate

Soil and climatic conditions in Newfoundland are on the margins of agricultural capability, and almost all feed grain is imported. The overall objective of this work was to develop guidelines for the production of barley in Newfoundland, with the goal of establishing modern cropping recommendations. We conducted a 4-year study near St. John's to examine the effect of seeding rate and topdress ammonium nitrate (N) fertilization rate on Chapais six-row barley ( Hordeum vulgare L.) yield components and grain yield. Increasing seeding rate from 200 to 380 seeds m^–2 did not alter grain yield in any year. Increasing topdress fertilization from 0 to 60 kg N ha^–1 increased spike density m^–2 at harvest, resulting in linear increases in grain yield in all years. Highest N rates had greatest lodging in two years. Based on our results, agronomic recommendations for eastern Newfoundland now include barley seeding rates of 250 ± 50 seeds m^–2, with topdress applications up to at least 30 kg N ha^–1.     

Effects of Nitrogen Fertilization and Date of Utilization on the Quality and Yield of Tall Fescue in Winter

There is no information available on the influence of nitrogen (N) fertilization on autumn‐accumulated forage under Central European conditions. In this context, the metabolizable energy and the degree of fungal infection have never been examined before. In this study, the effects of the amount of N fertilizer (0, 50, 100 and 150 kg N ha^?1), the date of N application (July and August) and the date of winter harvest (December, January and February) on the quality and dry matter (DM) yield of Festuca arundinacea stands in winter were investigated. DM yield, the metabolizable energy and digestibility of organic matter (= in vitro rumen fermentation technique), crude protein, ADL (acid detergent lignin), and for the first time ergosterol were determined. Disregarding the 0 variant, no interactions of any relevance were present. DM yield, crude protein and values of ADL increased with increasing amounts of N, but the concentration of energy decreased. The late N application resulted mostly in lower DM yields but kept the forage physiologically younger, which brought about higher levels of metabolizable energy and lower concentrations of ADL. With later date of harvest, losses of mass and quality occurred. The degree of fungal infection rose as the amount of N fertilizer increased. Three years of investigation under different weather conditions, including interactions with the effects of N fertilization, provide a good base for generalization.     

Chemical Composition and In Vitro Digestibility of Whole-Crop Pea and Pea–Cereal Mixture Silages Grown in South-western Quebec

The objective of this study was to determine the chemical composition and in vitro dry matter (IVDMD) and neutral detergent fibre (IVNDFD) digestibilities of silages made from whole‐crop pea [Pisum sativum L. (PS)], pea–wheat [Triticum aestivum L. (PW)], pea–barley [Hordeum vulgare L. (PB)] and pea–oat [Avena sativa L. (PO)] mixtures harvested 8 weeks (H8) and 10 weeks (H10) after seeding. Forty‐five days after ensiling, all forages were well ensiled as indicated by low pH and low water‐soluble carbohydrate content and high lactic acid concentration. Regardless of forage type, crude protein (CP) and IVNDFD were higher while starch and acid detergent lignin were lower in H8 than H10. However, harvest date had no effect on neutral (NDF) and acid (ADF) detergent fibre of the silages. Within each harvest date, CP was higher while NDF was lower for PS than pea–cereal silages. Differences in CP and fibre fractions between the pea–cereal mixture silages were not consistent for the two harvest dates. The IVDMD of PS was higher than that of the three pea–cereal mixture silages in H8 but was only higher than that of PB in H10. For the pea–cereal mixtures, IVDMD was higher for PO than PB and PW in H8 and was higher for PB than PW in H10. It was concluded that silage from pea monoculture had similar forage yields and a generally higher nutritive value than silages from pea–cereal mixtures.     

Reed Canarygrass Forage Yield and Nutrient Uptake on a Year-round Wastewater Application Site

Reed canarygrass (Phalaris arundinacea L.) is often planted at wastewater treatment sites to provide ground cover and remove nutrients. Our overall objective was to determine the forage yield and nutrient uptake under year-round potato wastewater application in northern latitudes. Specifically, we determined the effect of N fertilization rate on forage dry matter yield and N and P uptake by reed canarygrass, and compared the forage yield, persistence and nutrient uptake of reed canarygrass relative to those of orchardgrass (Dactylis glomerata L.), smooth bromegrass (Bromis inermis Leyss), timothy (Phleum pratense L.) and quackgrass [Elytrigia repens (L.) Nevski]. With only wastewater application, reed canarygrass had a forage yield of 5.8 Mg ha⁻¹, with N and P uptake of 113 and 30 kg ha⁻¹, respectively. Forage dry matter yield, N uptake and P uptake increased to 14.5 Mg ha⁻¹, 383 kg ha⁻¹ and 64 kg ha⁻¹, respectively, with an N fertilization rate of 224 kg ha⁻¹. Forage yield and N uptake of reed canarygrass, orchardgrass, timothy and smooth bromegrass were similar and exceeded those of quackgrass. Reed canarygrass P uptake exceeded that of the other grasses. Reed canarygrass was less persistent than quackgrass or smooth bromegrass.     

膜侧施肥对旱地小麦产量、籽粒蛋白质含量和水分利用效率的影响

覆膜栽培能提高旱地小麦产量,但降低了籽粒蛋白质含量,优化施肥是解决这一问题的有效措施之一。2013年9月至2016年9月,在黄土高原中部典型旱地进行田间定位试验,比较传统平作(不覆盖+均匀施肥)、垄覆沟播(垄上覆膜+垄间沟播+均匀施肥)和膜侧施肥(垄上覆膜+垄间沟播+播种行侧膜下定位施肥)栽培模式下,0~40 cm土层硝态氮含量和0~200 cm土壤水分,以及膜侧施肥对小麦氮素吸收利用、产量、籽粒蛋白质含量和水分利用的影响。与传统平作相比,在偏旱的2013—2014和2015—2016年度,垄覆沟播的小麦产量分别提高9.5%和6.3%,籽粒蛋白质含量降低7.1%和9.9%,水分利用效率提高5.8%和8.7%,而膜侧施肥的小麦产量提高18.8%和22.8%,籽粒蛋白质含量无显著变化,水分利用效率提高13.2%和19.6%;在偏湿润的2014—2015年度,垄覆沟播和膜侧施肥对小麦产量无影响,但膜侧施肥的籽粒蛋白质含量和水分利用效率分别提高6.0%和17.0%。与垄覆沟播相比,膜侧施肥在偏湿润年份使生长季内100~200 cm土壤水分消耗显著减少,而在偏旱年份使夏休闲季土壤蓄水显著增加,开花和收获期0~40 cm土壤硝态氮、根系全氮以及开花期茎叶全氮含量升高,促进了小麦营养器官氮素吸收、积累及其向籽粒的转运,提高了旱地小麦产量,籽粒蛋白质含量和水分利用效率。在偏干旱的2013—2014和2015—2016年度,膜侧施肥较垄覆沟播产量分别提高8.4%和15.5%,籽粒蛋白质含量提高9.9%和8.7%,水分利用效率提高7.0%和10.0%;在偏湿润的2014—2015年度,两处理产量无显著差异,但膜侧施肥的籽粒蛋白质含量提高6.0%。因此,膜侧施肥可维持旱地小麦生育后期的土壤氮供应,提高小麦产量、籽粒蛋白质含量和水分利用效率,增加下季播前深层土壤贮水,是适宜于旱区推广的小麦栽培模式。     

Nitrogen Sustains Seed Yield of Quinoa Under Intermediate Drought

Quinoa (Chenopodium quinoa Willd.) is a promising crop for food security in dry areas. Studies have been conducted to define nitrogen (N) fertilization levels and to understand the responses of quinoa to drought, but little is known about the response of this crop to N fertilization under drought stress. The aim of this study was to investigate whether N fertilization could improve quinoa yield and physiology under limited water. A greenhouse experiment was carried out with quinoa grown at four N fertilization levels (0, 0.2, 0.4 and 0.6 g N pot^?1) and two watering treatments (progressive drought and full irrigation; 10 and 98 % of pot water holding capacity, respectively). Results of this experiment showed that N may confer a certain degree of drought tolerance to quinoa as seed quality and yield of N‐fertilized plants were not affected by drought stress. Responses such as faster stomatal closure, reduced leaf water potential, higher leaf abscisic acid (ABA) concentration and particularly an improved N remobilization in N‐fertilized plants may have played a role in sustaining seed yield in the drought‐stressed treatment. These results under controlled conditions serve as a basis to elucidate drought tolerance mechanisms activated with N fertilization and to define the use of N in management practices under semi‐arid environments.     

苏丹草-黑麦草轮作制中施肥对饲料产量、养分吸收与土壤性质的影响

大田试验条件下采用苏丹草(Sorghum sudanense)与黑麦草(Lolium L.)轮作,分别设CK(不施肥)、NP(施氮磷肥)、NK(施氮钾肥)、PK(施磷钾肥)、NPK(施氮磷钾肥) 5个处理研究施肥对饲草产量、养分吸收及土壤养分的影响。结果表明,氮磷钾肥配施显著提高苏丹草与黑麦草鲜草产量,2005—2006年与2006—2007年两季饲草分别为162.7 t hm^-2、114.9 t hm^-2,分别比同期PK、NK、NP处理增产312.9%、26.9%、17.9%和338.5%、20.3%、17.2%。施肥影响饲草的氮、磷、钾含量,且氮磷钾配施可以改善饲草养分吸收,2005—2006年NPK处理的饲草N、P、K吸收量分别为500 kg hm^-2、91 kg hm^-2和997 kg hm^-2,2006—2007年NPK处理的饲草N、P、K吸收量分别为312 kg hm^-2、56 kg hm^-2和402 kg hm^-2。轮作系统中,氮磷钾肥配施条件下氮、磷盈余最少,而钾亏缺。在苏丹草-黑麦草轮作制中,随着种植次数的增多,各施肥处理土壤有机质、全氮均有不同程度上升,施磷(NPK、NP、PK)处理的速效磷、施钾(NPK、NK、PK)处理的速效钾均有上升,而NK处理的速效磷、NP处理的速效钾略有下降。     

Effects of harvest management on growth dynamics, forage and seed yield in berseem clover

Berseem clover (Trifolium alexandrinum L.) is an annual forage crop widely grown in Mediterranean environments. However, there is little information available on the patterns of accumulation and partitioning of assimilate in berseem and how this varies with harvest management, plant ontogeny or is influenced by genotype. Field experiments were conducted in Foggia (Italy) during three growing seasons (1991–92, 1992–93 and 1993–94), with the aim of evaluating the effects of different harvest managements on growth dynamics, forage yield and seed yield of one population of Egyptian (cv. ‘Giza 10’) as well as Italian (cv. ‘Sacromonte’) origin. Cutting treatments were applied at three different plant ages: sixth internode elongation (A), early flowering (B), and uncut control (C). The growth and development of the shoot and root systems were followed by destructive harvests made at about 5-day intervals during 9 weeks in spring in all treatments. Seasonal growth pattern, determined as dry matter accumulation, forage yield and seed production were greatly influenced by harvest management. The maximum value (20.5 g per plant on average) of dry weight was reached at about 250 days after sowing for treatment C. Defoliation induced a decrease of crown and root dry matter, however, as shown by the allometric relationships, the growth of roots and shoots was closely correlated and in most cases, shoot growth was higher than root growth and stem relative growth rate (RGR) was higher than leaf RGR. Berseem clover is a defoliation-tolerant species because after cutting, regrowth was accompanied by higher values of leaf-stem ratio (LSR), RGR and stem elongation rate (SER) than in control plants. The highest value for total forage yield (1.6 Kg m⁻²) and seed yield (60.5 g m⁻²) were obtained in treatment B and A, respectively. Plants cut at the sixth internode elongation showed a good seed yield and a small decrease (15%) in total forage yield as regards treatment B. Therefore, treatment A appeared the most favourable for obtaining double utilization (forage and seed yield) in a berseem crop. Berseem plants were greatly influenced by harvest treatments applied, but the response did not vary according to the genetic characteristics of the two cultivars examined.     

Genetic variation, heritability and genetic correlations for forage quality and yield traits of Mediterranean tall fescue germplasm

Higher ruminant intake potential and in vivo digestibility as indicated by lower neutral and acid detergent fibre (NDF and ADF), respectively, and higher crude protein (CP), may be valuable targets in tall fescue breeding. Some 105 full‐sib families from a diallel cross of Mediterranean parent germplasm were grown in a heated greenhouse simulating the temperature pattern of a Mediterranean environment, to estimate genetic parameters for NDF, ADF, CP and dry matter (DM) yield in one autumn and one winter harvest. Family x harvest interaction was large for NDF and ADF, moderate for CP and absent for DM yield. Additive genetic variance was mostly larger than specific genetic variance, and tended to be small for quality traits and large for DM yield. Narrow‐sense heritability was low for CP and ADF in autumn and moderate to fairly high in the remaining cases. Predicted gains per selection cycle never exceeded 5% for quality traits while being greater than 10% for DM yield. An inverse genetic correlation between DM yield and any quality trait emerged in the presence of sizeable genetic variation.     

光、氮及其互作对超级粳稻产量和物质生产特征的影响

大田条件下以超级粳稻南粳44和宁粳3号为材料,设置2种氮肥水平(N10:150 kg hm–2,N20:300 kg hm–2)和3种遮光处理(L1:不遮光,L2:抽穗前遮光20 d,L3:抽穗后遮光20 d),研究光、氮及其互作对超级粳稻产量和物质生产特征的影响。结果表明,较之L1,L2不仅减少了有效穗数和每穗粒数,导致总颖花量下降,降幅达24.81%~35.63%,而且还显著降低了抽穗期茎蘖数和叶面积指数,降幅达2.90%~6.44%和19.02%~27.17%,导致抽穗至成熟阶段的光合势、干物质积累量显著下降,最终产量显著下降,降幅达27.23%~35.26%。较之L1,L3主要影响了抽穗至成熟阶段的光合物质积累,导致结实率和千粒重显著下降,降幅达1.49%~4.48%和5.54%~9.17%,最终产量显著下降,降幅达10.91%~18.47%。L2条件下,随着氮肥水平增加,抽穗期茎蘖数与叶面积指数均显著增加,导致抽穗至成熟阶段光合势、干物质积累显著增加,最终有效穗数、每穗粒数、总颖花量以及产量显著提高。L3条件下,随着氮肥水平增加,抽穗至成熟阶段的光合物质积累显著提高,其中茎叶干物质向穗部转运量显著增加,转运率和贡献率也进一步提高,最终产量显著提高。由此可见氮肥施用能部分弥补因弱光逆境对超级粳稻物质生产及其产量的影响。     

刈割期与晾晒天数对饲料油菜产量和粗蛋白含量及水分的影响

为了明确长三角地区饲料油菜适宜收获期与晾晒时间,2016-2018年连续2年开展田间试验,终花至角果期刈割5次并于田间晾晒,比较不同刈割期和晾晒天数下饲草产量、粗蛋白含量及水分变化差异。结果表明,与首次刈割（终花期）相比,终花后4到16d刈割饲草鲜重显著增加,饲草干重分别提高了31.93%、41.50%、49.14%和61.43%。随着刈割时间延迟,饲草粗蛋白含量呈下降趋势,末次刈割饲草含水量显著降低（P<0.05）。油菜终花后4d刈割,并于田间晾晒第4和5天时,其鲜草含水量由82.16%下降为71.45%和65.26%。不考虑刈割期,田间原位晾晒3d,平均鲜草含水量由81.00%下降至66.30%。晾晒期间土壤累积温度每增加10°C,鲜草含水量降低2.30%。由此,长三角地区稻茬油菜在终花后4d刈割,饲草鲜产和粗蛋白含量均能达到较优水平,刈割后田间原位晾晒4~5d,可满足青贮水分要求。     

Potential decrease of grass tetany risk in rangelands combining N and K fertilization with MgO treatments

The most practical and effective method to increase dry matter production in rangelands is by adequate fertilization. N and K fertilizers have commonly been used worldwide to increase yield in rangelands. Fertilizers have a significant effect on mineral concentration in the forage. Risk of tetany, causing yield decrease and death in cattle, increases by feeding forage with a ratio of K/(Ca + Mg) ≥ 2.2. The fertilizers containing N and K are the most important factors increasing K/(Ca + Mg) ratio in forages. The present study has aimed to determine whether the tetany risks caused by K and N fertilization may be compensated by Mg fertilization. For this purpose, N (0 and 120 kg ha⁻¹), K (0 and 100 kg ha⁻¹) and Mg (0 and 30 kg ha⁻¹) were applied as combinations of each other. Each plot was separated into three sub-plots sampled on 25 April, 15 May and 5 June to determine Ca, Mg, K concentrations and K/(Ca + Mg) ratio.In this 2-year study, dry matter production in the control plot was 2064 kg ha⁻¹ and nitrogen application increased the dry matter production of the plots by about 100%. Dry weight ratios of grasses increased while legume dry weight ratios decreased drastically in response to N fertilization. An increase was observed in K/(Ca + Mg) ratio with N fertilization due to the fact that legumes have higher concentrations of Ca and Mg than grasses. K fertilization resulted in an approximately 30% increase of K concentration in dry matter. K/(Ca + Mg) ratio in plots where N and K were applied separately was lower than 2.2. However, K/(Ca + Mg) ratio in plots to which N and K were applied in combination was over 2.2, resulting in tetany risk. It is interesting to determine that Mg fertilization did not change Mg concentration in pasture. It was noted that tetany risk did not decrease with the advance of harvest dates. The results indicated that tetany risk caused by N and K fertilizations could not be compensated by Mg treatment. Therefore, it can be concluded that fertilization programmes avoiding legume decrease in rangelands may be useful to prevent the tetany risk.     

The Effects of Plant Population Density on the Growth and Chemical Composition of Lablab purpureus Grown for Fodder Production in a Semi-Arid Region

Lablab purpureus was grown in two 6-month field experiments in the Savannah region of Africa, with high rainfall and hot temperatures in the first 2 months, followed by low rainfall and cool temperatures until harvesting in January. The experiments evaluated the effects of plant population density (PPD), using rows at 70-, 110- and 150-cm intervals, on the yield and nutritive value of the crop, and the effect of an interim harvest on response to PPD. Lablab yield ha⁻¹ was increased to a greater extent by an increase in PPD from 110 to 70 cm interrow spacing than by an increase from 150 to 110 cm, and yield plant⁻¹ decreased as PPD increased to a greater extent for double-harvested than for single-harvested plants. This suggested that high PPD in the early stages of growth is important to promote high crop yields in this environment, probably because it mitigates drought effects in autumn. The effects of PPD on herbage composition were small and suggested that plant maturity had not been greatly affected by density. It is concluded that the maintenance of plant cover in the early stages of growth is important for high yields in the Savannah region, which can be achieved by an interrow spacing of no more than 70 cm and avoidance of an interim harvest.     

Genetic variation and selection criterion for digestibility traits of forage maize

Summary Variations in feeding value characteristics were studied on a factorial mating design, within a multilocal network. The in vitro digestibility of dry matter (IVDDM), neutral detergent fiber (NDF), acid detergent fiber (ADF), acid detergent lignin (ADL), starch, soluble carbohydrate, protein and ash contents were evaluated on whole plant samples. The in vitro digestibility of the non-starch and non-soluble carbohydrate plant part (IVDNSC) was also computed from near infra-red reflectance spectroscopy estimations of IVDDM, starch and soluble carbohydrate contents. Variations due to general combining ability (GCA) were more important, for all traits, than variations due to specific combining ability (SCA). Variations due to the GCA × environment interaction were also sizeable and were partly explained by the earliness of the lines. IVDDM was primarily influenced by the relative proportions of cell walls and starch in the whole plant, which were particularly susceptible to the development stage of the plants, at harvest. When adjusted for earliness, there was generally no significant relation between the line per se value and GCA performance in the biochemical constituent contents of the plant. On the contrary, IVDNSC seemed to be a feeding value trait worth evaluating at the inbred line level. It was also almost independent of the ripening stage and could be easily computed from whole plant samples. IVDNSC, with a simultaneous control of starch content, might be a good selection criterion for evaluating and improving the nutritive value of forage maize.