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。     

Potassium Management for Brown Midrib Sorghum × Sudangrass as Replacement for Corn Silage in the North-eastern USA

In recent years, there has been a growing interest in brown midrib (BMR) sorghum (Sorghum bicolor (L.) Moench.) × sudangrass (Sorghum sudanense Piper) hybrids (SxS) as a replacement for silage corn (Zea mays L.) in the north‐eastern USA. Recent studies suggest it is suitable for both rotational grazing and as a hay crop and could compete with corn harvested for silage in years when wet spring conditions prevent the timely planting of corn. However, little is known about its suitability as forage for non‐lactating cows that require low potassium (K) forages to prevent health problems. Our objective was to evaluate the impact of K fertilizer management (0, 112 or 224 kg K₂O ha^?1 cut^?1) under optimum N management (112–168 kg N ha^?1 cut^?1) on yield, quality and K concentrations of BMR SxS over a 2‐year period. Field trials were established on a fine loamy, mixed, active, mesic Aeric Fragiaquepts with medium K‐supplying capacity and characteristic of a large region in New York. Potassium application did not affect dry matter yields in either of the 2 years. Averaged over 2 years, neutral detergent fibre (NDF) significantly increased with K addition with similar but non‐significant trends observed in each of the years individually. The digestibility of NDF was unaffected by K application. Crude protein (CP) concentrations showed a significant decrease with K application in 2002 and similar trends were observed in 2003, although differences were not significant at P ≤ 0.05. The changes in NDF and CP did not significantly impact forage quality expressed as milk production per megagram of silage. Potassium application increased forage K concentration up to 13 mg K kg^?1 dry matter (in the first cut in 2003). Forage Ca and Mg concentrations decreased with K addition except for the first cut in 2002 where differences between 112 and 224 kg K₂O ha^?1 treatments were not significant. Without K addition in the 2‐year period, K concentrations in the forage decreased from 23 g kg^?1 for the first cutting in 2002 to 15 g kg^?1 for the second cut in 2003. Low K forage was obtained for all second‐cut forage unless 224 kg K₂O ha^?1 cut^?1 had been added. First‐cut forage was suitable only when no additional K had been applied. These results suggest low K BMR SxS forage can be harvested from initially high K soils without loss in dry matter yield as long as no additional K is added.     

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.     

Hay yield and nitrogen harvest in smooth bromegrass mixtures with alfalfa and red clover in relation to nitrogen application

An experiment was conducted in order to investigate hay yield and nitrogen harvest in binary smooth bromegrass (Bromus inermis Leyss cv. Tohum Islah) mixtures with alfalfa (Medicago sativa L. cv. Kayseri) and red clover (Trifolium pratense L. cv. Tohum Islah) in Erzurum, Turkey for 5 years between 1991 and 1995. The Hay yield, nitrogen harvest, protein concentration and land equivalent ratio (LER) in the mixtures with alternating rows of 1:1, 2:1 and 1:2 of smooth bromegrass with alfalfa and red clover were compared to those in pure legume stands without any N-fertilizer application or pure smooth bromegrass stands that received 0, 50, 100 and 150 kg ha⁻¹ N. The mixtures had no N fertilization apart from 40 kg N ha⁻¹ in the establishment year. The dry matter production in all the mixtures receiving no N fertilizer application was higher than in pure legume stands. Pure grass stands were sustained only with the application of 150 kg ha⁻¹ N. The highest hay yields were obtained from the mixtures of smooth bromegrass (Sb) with red clover (Rc) (2Rc 1Sb) (14.65 t ha⁻¹) and with alfalfa (A) (1A 1 Sb) (14.49 t ha⁻¹). Although N application increased Sb yields in pure stands, the highest yields obtained with N fertilization were still lower than the yields in the mixtures without N application. The superiority of the mixtures was also reflected by their large N harvests (e.g. 355.9 kg N ha⁻¹ in 2Rc 1Sb plots) compared to pure Rc (317.8 kg N ha⁻¹), pure A (294.3 kg N ha⁻¹) and pure Sb stands that received 150 kg N ha⁻¹. The nitrogen harvest increased in pure Sb plots as the N doses applied increased. Furthermore, the protein concentration of the hay from the mixtures (158.2–165.7 mg g⁻¹) was equal to that of the pure A stands (165.7 mg g⁻¹) and higher than that of pure Sb stands (122.9 mg g⁻¹ at 150 kg N ha⁻¹ application) although the hay from pure Rc plots had the highest protein concentration (179.3 mg g⁻¹). The LER values were also higher in the mixtures (e.g. 1.28 in 1A 1Sb and 1.28 in 2Rc 1Sb plots) compared with the pure stands. The mixture plots also had a more balanced temporal distribution of hay. The grass component was more productive in early spring, whereas the legume fractions grew better in the summer. In conclusion, for a sustainable production of high-quality hay and greater N harvests without using N fertilizers, binary mixtures of Sb with A in alternating rows (1A 1Sb) were recommended for long-purpose stands and in alternation with double red clover rows (2Rc 1Sb) for short purpose stands under similar conditions. N application could be eliminated in the grass–legume mixtures without any yield depression.     

Effect of Phosphorus and Nitrogen Fertilization on Sunflower (Helianthus annus L.) Nitrogen Uptake and Yield

Little is known about the effect of combined phosphorus and nitrogen (P‐N) fertilization on the N requirement of sunflower (Helianthus annus L.). This study was carried out to evaluate the effects of varying levels of P and N, as well as the interaction P × N, on the N uptake, yield and N apparent utilization efficiency under field conditions. Split‐plot design experiments were conducted in the mid‐western Pampas in Argentina. Four levels of N (0, 46, 92 and 138 kg N ha^?1) and three levels of P (0, 12 and 40 kg P ha^?1) were applied to two Typic Hapludolls over two growing seasons (1997–98 and 1998–99). N uptake and soil N‐NO₃ contents were determined at the V₇, R₅ and R₉ growth stages. The sunflower yield ranged from 2.5 to 5.0 Mg ha^?1. The total N requirement was around 45 kg N Mg^?1 grain, and this result suggests that it is not necessary to use different N requirements (parameter b) for fertilized crops when a yield response is expected. To achieve a 100 % yield maximum a N supply (soil plus fertilizer) of 181 kg N ha^?1 at P₄₀ was needed. However, at P₀, the highest yield was about 80 % of the maximum yield with a N supply (soil plus fertilizer) of 164 kg N ha^?1. P application increased the apparent use efficiency of the supplied N.     

Management of Italian and Perennial Ryegrasses for Seed and Forage Production in Crop Rotations

Italian ryegrass (Lolium multiflorum Lam.) and perennial ryegrass (L. perenne L.) can be grown for seed and forage in cold winter regions provided the stand persists well over winter. Seed yield and plant characteristics during primary growth, and forage yield during regrowth, were determined for two Italian and one perennial ryegrass cultivars in Atlantic Canada. Establishment methods and dates included sowing ryegrass in cultivated soil alone or with barley in mid‐May and, after harvesting the barley crop, by sowing ryegrass following conventional or reduced cultivation and by no‐till drilling into barley stubble in mid‐August and early September. Despite some winterkill, particularly in Italian ryegrass, seed and forage yields were adequate in post‐establishment growing seasons. Seed yield for Italian ryegrass was greatest (1270 kg ha^?1) when it was sown into cultivated soil in mid‐August and least (890 kg ha^?1) when sown alone in May. Italian ryegrass yielded 15–17 % more seed when plots were established in mid‐August rather than in mid‐May or early September. Italian ryegrass cv. Lemtal had a greater density of fertile tillers (1030 m^?2) in the sward than cv. Ajax (860 m^?2) and its tiller density was greater when seeded into cultivated soil in September than in mid‐August. There were fewer spikelets per seed head for sowing Italian ryegrass with barley in May than for the other methods of establishment. Forage yield in regrowth was greater for Italian ryegrass cv. Ajax (2770 kg ha^?1) than for cv. Lemtal (2480 kg ha^?1). Seed yield of perennial ryegrass was greater when seeded in mid‐May than in mid‐August or early September. The seed yield of perennial ryegrass was greater when it was sown with barley in May and harvested for grain, than when it was sown alone or with barley harvested at late milk stage. The establishment methods for mid‐August and early September sowing had little effect on seed yield. However, the no‐till and reduced tillage methods resulted in a greater tiller density than sowing into the cultivated seedbed. Fertile tillers tended to be denser under reduced cultivation for sowing in August. Forage yield of perennial ryegrass regrowth was not influenced by the sowing method and timing. In conclusion, Italian and perennial ryegrasses produce adequate seed and forage regrowth under different establishment methods and timing. However, the poor persistence of Italian ryegrass may limit commercial production after the establishment year in Atlantic Canada.     

Growth and Yield of Sweet Corn Following Green Manure in a Warm Temperate Environment on Sandy Soil

Legumes used as green manure (GMN) may provide on‐farm sources of N for subsequent crops. In warm‐humid climates on sandy soils, however, there is a need to evaluate effects on growth and yield of subsequent crops when GMN substitutes for chemical N fertilizer. We collected time‐series data for 2 years to evaluate growth and ear yield response of sweet corn (Zea mays L. var. Rugosa) in annual rotation with GMN (summer, winter or summer plus winter GMN) and supplemented with 0, 67 or 133 kg chemical N ha⁻¹. Control treatments receiving 0, 67, 133, 200 or 267 kg chemical N ha⁻¹ were used for comparison. Rotation with summer plus winter GMN resulted in more growth and yield benefit for sweet corn than did the other GMN rotations. Compared with control treatments receiving the same chemical N rates, rotation with summer plus winter GMN increased sweet corn ear yield, leaf area index and total plant dry weight and N content by 15–30 %. Despite these benefits, use of high chemical N rate (267 kg chemical N ha⁻¹) resulted in ear yields at least 20 % greater than sweet corn rotated with any GMN and fertilized with reduced N rates. Largest increases in sweet corn dry weight and N content occurred between 4 and 6 weeks after emergence in all treatments. After this period of rapid growth, sweet corn fertilized with 267 kg chemical N ha⁻¹ showed higher N content than all other treatments. Prior to this period of rapid growth, multiple rainfall events in excess of 30 mm may have resulted in leaching of N from GMN residue. Considering the high rainfall levels, low water and N retention capability of sandy soils and rapid N release from GMN during decomposition, future research of GMN in this environment should evaluate options to better match GMN termination with time of greatest potential N uptake from a subsequent crop.     

Winter Wheat Cultivar Responses to Fungicide Application are Affected by Nitrogen Fertilization Rate

Foliar fungicides are important management inputs for winter wheat (Triticum aestivum L.) in high-yielding areas of Europe, but their effectiveness may interact with cultivar selection and nitrogen (N) fertilization. No information is available on the potential use of fungicides in reducing yield losses from foliar diseases in Croatia, where wheat crop is extensively grown under low N inputs. Field experiments were conducted during 2000–02 to evaluate the agronomic responses of six winter wheat cultivars to fungicide application (tebuconazol around heading) compared with untreated plots at low (67 kg N ha⁻¹) and high (194 kg N ha⁻¹) N fertilization rates. Grain yields tended to increase in all years following fungicide treatment at high N rate by an average of 10.1 % (773 kg ha⁻¹), but improved significantly in one year only at low N rate. When these occurred, yield increases were associated with larger grain weight per ear primarily due to heavier 1000-kernel weight. Cultivars differed in their responses to fungicide application across growing seasons and N fertilization rates. Under low disease pressure in 2000 and 2001, improved yields with fungicide use occurred for few susceptible cultivars only, whereas all cultivars significantly increased yields under higher disease severity in 2002 by an average of 383 kg ha⁻¹ (5.0 %) at low N rate and 1443 kg ha⁻¹ (19.0 %) at high N rate. Following fungicide application at high N rate, some susceptible cultivars outyielded resistant cultivars, whereas opposite responses occurred in untreated plots. High N fertilization rate consistently produced larger grain yields except under high disease severity and no fungicide sprayed in 2002, when it had no benefits at all over low N rate. Fungicide application showed limited importance for wheat performance at low N rate; however, cultivars significantly differed in yield responses as well as in rankings after fungicide use at high N fertilization rate.     

Impact of Nitrogen and Plant Growth Promoting Rhizobacteria on yield and yield components of sunflower in a glasshouse environment

The effects of Nitrogen (N) and Plant Growth Promoting Rhizobacteria (PGPR) on growth and development of sunflower (Helianthus annuus L. var. Hysun-33) grown in the greenhouse under a natural environment were studied. The N-use efficiency of a sunflower crop grown under three N rates (N₁ = 0 kg ha^?1, N₂ = 120 kg ha^?1, and N₃ = 240 kg ha^?1) and three PGPR levels (R₁ = 0 kg ha^?1, R₂ = 30 kg ha^?1, and R₃ = 60 kg ha^?1) were investigated. The maximum amount of N resulted in higher total dry matter production per plant and the effect was prominent from 34 days after sowing (DAS). Seed yields differed significantly among different sunflower crops especially at limiting N supply, with significant shifts according to the N level. N uptake was an important parameter for yield at all N rates. The 240 kg N ha^?1 treatments provided the maximum yield, while the oil contents in these treatments of higher yield showed a lower oil content (%). Harvest index was also significantly correlated to yield across N rates; however, its importance depended much on environmental conditions as well. It can be inferred from the study that sunflower crop is well-supplied with respect to growth, development, yield and yield components, to enhance N efficiency and depends very much on the N supply. All the parameters gave maximum results with the increment of N while PGPR regimes had no prominent impact on the sunflower crop, the target environment, and the target yield level grown under a specified controlled glasshouse environment.     

Forage production,quality and water-use-efficiency of four warm-season annual crops at three sowing times in the Loess Plateau region of China

Increasing demand for livestock products is driving development of livestock systems worldwide. That requires improved and new forage production options. The Loess Plateau region in central-northern China is an important area for livestock production, as it supports11% and 19% of the country’s cattle and sheep, respectively (China statistical yearbook 2014). The rain-fed semi-arid environment of the Loess Plateau means that maximizing the water-use-efficiency (WUE) of forage production is vital to guarantee enough fodder supply the livestock demand. A three-year field experiment in north-west Loess Plateau compared forage production, water use and water-use-efficiency as well as crude protein (CP) content of forage maize, Sudan grass, foxtail millet and Japanese millet sown at three sowing dates according to the opening rain during 2011–2013. On average, forage maize produced the highest biomass (12.1 t ha⁻¹) and had the highest WUE (43.4 kg DM ha⁻¹ mm⁻¹). This was followed by Sudan grass (7.8 t ha⁻¹; 26.5 kg DM ha⁻¹ mm⁻¹), Japanese millet (6.7 t ha⁻¹; 26.2 kg DM ha⁻¹ mm⁻¹) and foxtail millet (6.7 t ha⁻¹; 24.6 kg DM ha⁻¹ mm⁻¹). Optimizing sowing date played an important role in maximizing forage production and WUE of all tested forages. Compared to the earliest sowing date, a delay of two weeks reduced forage production by 17% in maize, 35% in foxtail millet, and 16% in Japanese millet. A delay of four to six weeks reduced biomass yield by 58% in maize, 57% in foxtail millet, and 56% in Japanese millet. Late sowing also greatly reduced WUE of forage maize and foxtail millet by 33% and 42%, respectively, when compared to early sowing. The middle sowing date maximized forage production and WUE of Sudan grass in two of the three growing seasons, which was 20% and 38% higher than the early and late sowing, respectively. Late sowing in all forages reduced crop water use by 42–57 mm compared to the early sowing. Among four test crops, CP of Sudan grass (7.9%) and forage maize (7.7%) was higher than foxtail millet (6.8%) and Japanese millet (6.7%). Compared with early sowing, CP_f in late sowing significantly increased in Sudan grass and decreased in Japanese millet, in contrast, no evident sowing date effect was found in forage maize and foxtail millet. This study showed that all four warm-season annual grasses had high forage production potential, forage maize was the most reliable and efficient option. Forage maize and the millets could easily be integrated into existing cropping systems and provide opportunities as both grain and forage-producing crop to provide added flexibility for farmers.     

Impact of Phosphorus from Dairy Manure and Commercial Fertilizer on Perennial Grass Forage Production

Increased recovery and recycling of manure phosphorus (P) by crops on dairy farms is needed to minimize environmental problems. The main objective of this study was to compare P utilization by orchardgrass (Dactylis glomerata L.) and tall fescue (Festuca arundinaceae Schreb.) from dairy manure or inorganic fertilizer. The study was conducted from 1994 to 2000 at the Cornell University Baker Farm, Willsboro, NY, on a somewhat poorly drained Kingsbury clay (very–fine, illitic, mesic Aeric Epiaqualfs). The design was a split‐plot in a randomized complete block with two manure rates (16 800 and 33 600 kg ha^?1) and one nitrogen (N) fertilizer rate (84 kg N ha^?1 at spring greenup and 56 kg N ha^?1 prior to each regrowth harvest) as the main plots and grass species as subplots replicated six times. Fertilizer P [Ca(H₂PO₄)₂] was applied to the fertilizer treatment in 1995 and 1996 at 11 kg P ha^?1 year^?1. Orchardgrass P removal averaged 21 % higher than tall fescue P removal for the spring harvest, but orchardgrass averaged 24 % lower P removal than tall fescue removal for all regrowth harvests from 1995–99. Phosphorus herbage concentration in the fertilizer treatment was in the range of 1.9–2.7 g P kg^?1 compared with 2.2–5.3 g P kg^?1 in the manure treatments. Seasonal P removal ranged from as low as 9.2 kg P ha^?1 to as high as 48.5 kg P ha^?1. Morgan extractable soil P in the top 0–0.20 m remained high through 1999, with 29.1 kg P ha^?1 at the highest manure rate in tall fescue compared with 8.4 kg P ha^?1 measured in 1993 prior to the experiment. In 2000, soil P at the highest manure rate in tall fescue dropped to 10.1 kg P ha^?1, following cessation of manure application in 1998. Intensively managed harvested orchardgrass and tall fescue have the potential to remove large quantities of manure P.     

Maize Grain Yield Response to Tillage and Fertilizer Nitrogen Rates on a Tara Silt Loam

Effects of tillage on the appropriate fertilizer N applications needed to achieve maximal grain yield are poorly denned. The study objective was determination of relative corn grain yield response to N application rate for four tillage practices: no-tillage (NT), ridge tillage (RT), fall chisel plowing (CP) and fall moldboard plowing (MP). Maize (Zea mays L.) grain yield and N accumulation were monitored over a 6 year period with the same tillage treatment and the same fertilizer N rate applied each year to each plot. Two hybrids, differing in relative maturity rating, were planted each year. Fertilizer N rates ranged from 10 to 190 kg ha^?1 and consisted of 10 kg ha^?1 of liquid starter N applied at planting with varying amounts of fall applied anhydrous ammonia. With only starter fertilizer, grain yields increased with tillage intensity in the order NT ≤ RT ≤ CP ≤ MP. With ≥ 55 kg total applied Nha^?1, 6 year average grain yields were unaffected by tillage. Total N removed in grain annually with only starter fertilizer ranged from 25–85 kg ha^?1 Maximal amounts of N removed, about 145 kg N ha^?1, occurred with 100–145 kg applied N ha^?1 for all tillage treatments under the more favorable climatic conditions. Several interactions affecting grain yield appear climatically sensitive with exception of tillage by fertilizer N interactions. Because of variability in climate, planting dates varied by almost 4 weeks. Relative yield loss due to planting delay were Fertilizer N (mean change ??124 –?275 kg ha^?1 day^?1) > Starter N only and MP (mean ?? 259 kg ha^?1 day^?1) > other tillages in general. Yield loss due to delayed planting ranged from 0.0–275 kg ha^?1 day^?1. Grain yield gains due to early spring soil temperatures were 16.0–21.8 kg ha^?1 index-degree^?1 with MP tillage and averaged 2.7– 16.7 kg ha^?1 index-degree^?1 more than those of other tillage-hybrid combinations.     

乙烯利和氮肥对夏玉米氮素吸收与利用及产量的调控效应

以玉米品种"郑单958"为材料,在大田条件下,研究了乙烯利(0和180 g hm–2)和氮肥水平(0、75、150和225kg N hm–2)对夏玉米产量、氮素吸收和利用以及SPAD值的影响。结果表明,乙烯利处理显著降低了氮吸收量和吸收效率,但显著提高氮利用效率,其中乙烯利处理氮农学效率比对照提高了32.7%~34.6%,而且乙烯利处理对玉米产量及其产量构成因素没有显著影响;随着施氮量增加,夏玉米产量、产量构成因素和氮吸收量显著增加,而氮吸收效率、氮利用效率、氮偏生产力和氮农学效率随之降低,其中225 kg N hm–2处理氮吸收量比0 kg N hm–2处理提高了68.4%~91.8%,但225 kg N hm–2和150 kg N hm–2处理之间的氮吸收量差异不显著。乙烯利和氮肥对氮吸收量、氮吸收效率和氮农学效率具有互作效应。喷施乙烯利和增施氮肥均能提高灌浆期穗位叶SPAD值,但两者之间没有互作效应。通过相关性分析表明,夏玉米产量与吐丝期氮吸收量、收获期氮吸收量、灌浆期穗位叶SPAD值显著正相关。     

Improved persistence of red clover (Trifolium pratense L.) increases the protein supplied by red clover/grass swards grown over four harvest years

UK livestock agriculture can significantly reduce its protein imports by increasing the amount of forage based protein grown on-farm. Forage legumes such as red clover (Trifolium pratense L.) produce high dry matter yields of quality forage but currently available varieties lack persistence, particularly under grazing. To assess the impact of red clover persistence on protein yield, diploid red clover populations selected for improved persistence were compared with a range of commercially available varieties. All populations were grown over four harvest years in mixed swards with either perennial ryegrass (Lolium perenne L.) or perennial plus hybrid ryegrass (L. boucheanum Kunth). Red clover and total sward dry matter (DM) herbage yields were measured in Years 1–4, red clover plant survival in Years 3 and 4 and herbage protein (CP) yield and concentration in Years 2 and 4. In general, red clover DM yield in year 4 (3.4 t ha⁻¹) was lower than in year 1 (13.9 t ha⁻¹) but the red clover populations differed in the extent of this decline. Differences in the persistence of the red clover populations in terms of plant survival and yield were reflected in the contribution of red clover to the total sward yield in Year 4, which ranged from 61% for the highest yielding population, AberClaret, to 11% in the lowest yielding, Vivi. Increased red clover DM yield was reflected in a greater CP yield (protein weight per unit area), which ranged from 1.6 t ha⁻¹ year⁻¹ to 2.9 t ha⁻¹ year⁻¹ in Year 2 and from 1.1 t ha⁻¹ year⁻¹ to 1.9 t ha⁻¹ year⁻¹ in Year 4. CP concentration (protein weight per unit herbage weight) of all of the red clover populations was within a range considered suitable for ruminant production. The implication of these results for the future use of red clover in sustainable grassland systems is discussed.     

Genetic variation within eight populations of perennial forage grasses

Information on both mean performance and genetic variation is important in determining the value of germplasm for breeding via recurrent selection. The objectives of this experiment were to evaluate different methods of controlling spatial variation for forage yield, and to estimate genetic variances and heritability in eight perennial forage grass populations. Polycross families of two populations of smooth bromegrass (Bromus inermis Leyss.), two populations of hybrid wheatgrass (Elytrigia×muctonata (Opiz ex. Bercht.) Prokud.), and four populations of orchardgrass (Dactylis glomerata L.) were field tested for 2 years. Spatial variation was present in all three progeny tests, but was well accounted for by either the incomplete block design or a nearest neighbour analysis (NNA) of yield potentials. Low rank correlations between adjusted family means for the incomplete block design vs. the NNA created the unanswered question of which would provide a more appropriate estimate of family mean performance. Genetic variation was detected in six out of eight populations for forage yield, four out of six populations for ground cover, all four orchardgrass populations for maturity and one of four orchardgrass populations for leafspot reaction (caused by Drechslera spp.). Excessive year-family interactions prevented detection of genetic variation for leafspot reaction in the other populations. Heritability estimates ranged from 0.30 to 0.42 for forage yield. In all three species, there was a trend toward a negative relationship between population mean and genetic variance, suggesting that less elite populations may need to contribute other traits to be useful in the short term.     

Productivity and Sustainability of Cotton (Gossypium hirsutum L.)–Wheat (Triticum aestivum L.) Cropping System as Influenced by Prilled Urea, Farmyard Manure and Azotobacter

Field experiments were conducted at Indian Agricultural Research Institute, New Delhi, during 2001–2002 and 2002–2003, to study the effect of inorganic, organic and Azotobacter combined sources of N on cotton (Gossypium hirsutum L.) and their residual effect on succeeding wheat (Triticum aestivum L.) crop. The results indicated considerable increase in yield attributes and mean seed cotton yield (2.33 Mg ha^?1) with the combined application of 30 kg N and farmyard manure (FYM) at 12 Mg ha^?1 along with Azotobacter (M₄). The treatment in cotton that included FYM, especially when fertilizer N was also applied could either improve or maintain the soil fertility status in terms of available N, P and K. Distinct increase in yield attributes and grain yield of wheat was observed with the residual effect of integrated application of 30 kg N ha^?1 + FYM at 12 Mg ha^?1 + Azotobacter. Direct application of 120 kg N ha^?1 resulted 67.4 and 17.7 % increase in mean grain yield of wheat over no N and 60 kg N ha^?1, respectively. Integrated application of organic and inorganic fertilizer is therefore, recommended for higher productivity and sustainability of the cotton–wheat system.     

不同施氮水平对超高产夏玉米氮磷钾积累与分配的影响

为探明不同施氮水平下玉米超高产(≥13 500 kg hm^-2)群体氮磷钾积累及分配规律,通过苏玉20、浚单20两品种3年不同氮肥运筹方案的试验,实现了籽粒最高产量14 753 kg hm^-2的目标。结果表明：(1)随着生育进程,两品种氮磷钾在植株、籽粒中积累逐渐增大,在叶片、茎秆、叶鞘中呈先单峰变化趋势,叶片氮钾峰值在大口期,磷峰值在开花期。增大灌浆期植株氮积累量及叶片氮转移率,促使成熟期籽粒氮磷较大积累量,利于超高产玉米群体的形成。(2)籽粒产量、1 kg氮生产籽粒量、氮肥的农学效率、氮素利用率、植株(及叶片、茎秆、叶鞘、籽粒等器官)氮磷钾含量在450 kg hm^-2施氮水平时达到最大值,其值(苏玉20)分别为14753 kg hm^-2、44.0 kg、19.24%、38.63%、335.4 kg hm^-2、178.2 kg hm^-2、230.7 kg hm^-2,过高过低施氮均使氮磷钾积累量及产量下降。(3)由两品种产量与施氮水平的回归方程,确定了超高产时的最佳施氮量、超高产施氮水平和最佳施氮范围,苏玉20分别为457.0 kg hm^-2、418.3~495.7 kg hm^-2、418.5~495.4 kg hm^-2;浚单20分别为452.7 kg hm^-2(最佳施氮量)、410.8~494.6 kg hm^-2 (最佳施氮范围)。     

Yield and nitrogen utilization efficiency of the pseudocereals amaranth,quinoa, and buckwheat under differing nitrogen fertilization

In recent years, the cultivation of the pseudocereal species amaranth, quinoa, and buckwheat has gained rising attention. This study was undertaken to explore nitrogen (N) fertility requirements and nitrogen use efficiency of these species. For this purpose, a 2-year field experiment with N rates of 0, 80, and 120 kg N ha⁻¹ for amaranth and quinoa and 0, 30, and 60 kg N ha⁻¹ for buckwheat and two cultivars of each species was conducted.Grain yield of amaranth responded to N and ranged between 1986 and 2767 kg ha⁻¹. Nitrogen utilization efficiency (NUtE) ranged from 13.9 to 15.4 kg grain yield per kg above-ground plant N and decreased with increasing N rate. Higher grain yields and NUtEs seemed to be mainly inhibited by the low harvest index (0.22–0.23) of the investigated amaranth cultivars.Quinoa yielded between 1790 and 3495 kg grain ha⁻¹ and responded strongly to N fertilization. NUtE averaged 22.2 kg kg⁻¹ and did not decrease with increasing N rates.The grain yield of buckwheat did not respond to N fertilization and averaged 1425 kg ha⁻¹. N uptake increased only slightly with N fertilization. NUtE ranged from 16.1 to 20.0 kg kg⁻¹. Main problems occurring with the application of N to buckwheat were grain scattering and lodging.     

The Effect of Fertilizer Type and Level of N Fertilization Before and After Grassland Renewal on N Leaching Losses

When grassland is ploughed and reseeded this results in an increased mineralization of organically bound nitrogen (N) in the soil. Greater amounts of nitrate in autumn are at risk of being leached during the winter half of the year. In two field experiments, nitrate leaching was measured over 2 years after reseeding of a 9‐year‐old grassland field in spring on a sandy soil in northwest Germany. During the experiments, major management factors that can influence the intensity of mineralization were varied: Type of fertilizer, mineral N fertilizer or organic manure, and the level of fertilization, 0, 160 or 320 kg N ha⁻¹ a⁻¹, before renewal of the grassland, and level of fertilization, 0, 160 or 320 kg N ha⁻¹ a⁻¹ in mineral form, after renewal of the grassland. The type of fertilization as well as the level of N fertilization before ploughing had no significant effect on the soil mineral nitrogen content (SMN) in autumn and N leaching in the year following the grassland renewal. N fertilizer level after sward renovation had a significant effect on the nitrate leaching losses in the two following years. Fertilization at a rate of 320 kg N ha⁻¹ resulted in leaching losses of 7 and 61 kg N ha⁻¹ in the first and second subsequent years, respectively. At fertilizer rates of 0 and 160 kg N ha⁻¹ leaching losses were lower than 5 kg N ha⁻¹. It is concluded that for mown grassland no restriction of the N fertilization before the renovation of the sward is necessary to reduce the nitrate leaching risk as long as the amount of N fertilized does not exceed the N‐uptake by the crop. Similarly, the N fertilization after the sward renewal does not bear a particular leaching risk.     

Effects of Nitrogen and Foliar Sulphur Interaction on Grain Yield and Yield Components in Barley

In this study, conducted from 1979 to 1986 in southern Spain, the objective was to analyze the effects of a possible interaction between soil-applied N and foliar S applied to barley (Hordeum vulgare L.) during tillering on grain yield and to identify the mechanism involved. From 1979 to 1982, we used rates of 20, 40, 60 and 80 kg a.i. N ha^?1, together with 12.5 or 25 kg foliar a.i. S ha^?1 during tillering. The results demonstrated that foliar S at both dosages acted as a partial (but not total) substitute for N, when the latter was applied at levels of 40 to 60 kg ha^?1. These effects of S did not appear to result only from a nutritive mechanism, but rather from a hormonal mechanism through the increase in ethylene biosynthesis. Therefore, during 1983 to 1986, we used 40, 60 and 80 kg a. i. N ha^?1, together with 12.5 a. i. S ha^?1 and 0.55 kg a.i. ethrel (2-chloroethyl-phosphonic acid) ha^?1. The results showed that the effects of S and ethrel on yield were practically the same. Assayed with 40 and 60 kg N ha^?1, S and ethrel acted as partial (but not total) substitutes for N, exceeding the yield of the control without S or ethrel, and equalling the yield obtained with 20 kg more of N ha^?1. The S or ethrel applied with 80 kg N ha^?1 presented an additive effect with the N. The increases in yield using S or ethrel were in all cases due to the increased final number of spikes m^?2, which was principally a consequence of the higher number of tillers formed but also a result of increased survival of tillers to form a viable spike. In addition, the positive effects of S on yield were greater the smaller the N dosage and the lower the annual yield. Finally, we present a possible mechanism of hormonal action, to explain how foliar S applied during tillering affects grain yield in barley.