川中丘陵区农牧结合模式的研究

本文以川中丘陵区的大足县作为研究典型,分析了该县农业生态系统的现状和问题,并提出了以牧草为中心的农牧结合新模式。结果表明,该模式能扭转农业生态系统的恶性循环,促进农、林、牧、副、渔五业的发展。     

四种禾草株高生长进程差异分析

研究四种禾本科草类（冷地早熟禾、星星草、紫羊茅和草地早熟禾）在西宁地区的株高生长进程。结果表明：在生育期内禾草的生长速度不一致，生长曲线呈Ｓ形；用对称Ｓ形曲线模拟和Ｌｏｇｉｓｔｉｃ生长曲线模拟后，四种禾草的Ｓ形曲线间有差异，因而生长高峰期的到来也有差异，草地早熟禾出现最早，为返青后的第３８（或３９）ｄ，紫羊茅出现最晚，为返青后的第５４（或５５）ｄ，平均生长速度和最大生长高度也有差异，冷地早熟禾最大，分别为０．５６ｃｍ／ｄ和５６ｃｍ，草地早熟禾最小，分别为０．３８ｃｍ／ｄ和３０ｃｍ。     

Azuche, Hymenachne amplexicaulis (Rudge) Nees, Forage Genetic Resources for Floodplains in Tropical Mexico

Azuche Hymenachne amplexicaulis (Rudge) Nees is a C₃ grass native to tropical flooded areas in South and Central America with 2n = 2x = 24 chromosomes. During 2002 and 2003, the Graduate College for Agricultural Sciences (CP) and the Mexican Institute for Forestry, Agriculture and Animal Production Research (INIFAP) organized an expedition to collect the genetic diversity of this species within tropical Mexico, in order to preserve and study it under nursery conditions. The collection was performed from Puerto Vallarta to Tapachula on the Pacific and from Palizada, Campeche to Veracruz on the Gulf of Mexico coast, and also crossing sections through the Tehuantepec isthmus and through the Sierra Madre de Chiapas. Ninety sites were sampled, on each, 25 tillers were collected, tagged and stored in a commercial soil mix until establishment of individual plants within 6 l pots. The largest Azuche prairie observed had a 10 ha surface, with the grass limited to small surfaces of up to 0.25 ha. It was not found on places with salty water, even seasonally. The Pacific coastal side is less abundant in niches for this species. Producers’ experience indicated that this grass is beneficial for milk production compared with other forage grasses, mainly C₄, growing in flooded areas. Initial studies of genetic diversity showed wide morphological variation for sprouting ability, leaf width and length among samples. Azuche diversity showed good potential production attributes for farm and wild animals, under flooding tropical savanna conditions.     

几种冷季型草坪草在关中地区的引种试验

通过对5种引种草坪草的物候期、覆盖度、生长速度、生物量及抗逆性等方面的综合研究,结果表明:5种草坪草均适宜在陕西关中生长.多年生黑麦草Lolium perenne品种爱神特和佳丽2号抗性较差;其中爱神特生长速度比佳丽2号快;而佳丽2号植株低矮、生长缓慢,可以减少修剪次数,降低管理成本.高羊茅Festuca arundinacea品种贝克、美洲虎3号和火凤凰绿期较黑麦草长,尤其是抗性强,对环境条件的要求较低,其中火凤凰更适合于高温干旱低养护管理的条件.     

Effect of drought on biomass allocation in two invasive and two native grass species dominating the mixed‐grass prairie

Control of exotic plant species invading the native prairie relies on our understanding of the eco‐physiological mechanisms responsible for the spread of these species as they compete with native plants for soil resources. We used a greenhouse pot experiment to study vegetative biomass allocation in response to drought stress in two exotic grass species, Kentucky bluegrass (Poa pratensis L.) and smooth brome (Bromus inermis Leyss), and two native species, western wheatgrass (Pascopyrum smithii (Rydb.) A. Löve) and green needlegrass (Stipa viridula Trin.). The experiment was conducted over 3 months in 2010 and again in 2011 in a factorial design of four species and two drought treatments. The proportional data of biomass allocation to shoots, roots, rhizomes and crowns (shoot base) of grass seedlings were analysed by both the nonparametric Mann–Whitney U‐test on the original data and one‐way anova on the arcsine‐transformed data. Our data suggest a clear distinction between the two invasive and two native species in potential competitiveness in soil resource use, with the two exotic species having higher biomass allocation to roots than the two native species and the native species having a higher biomass allocation to crowns than the two exotic species. It is interesting to note that the strongly rhizomatous smooth brome did not produce rhizomes in the first season's growth, regardless of the water stress level. The effect of drought stress on biomass allocation manifested itself more on rhizomes or crowns than on roots or shoots of the four studied grass species, with the effects species‐specific in nature.     

4种多年生禾本科牧草种子收获方法的研究

[目的]研究4种多年生禾本科牧草在3种收获方式下的产量损失情况。[方法]以人工完全收获为参照,研究了谷物联合式收割机直接收获法与人工分段收获法在4种多年生禾本科牧草种子收获过程中的产量损失情况,同时研究了不同清选方式对种子质量的影响,分析了农户人工筛选种子的质量水平。[结果]扁穗冰草和新麦草适合于联合收割机直接收获,与人工完全收获的产量相比,收获率分别达到76.0%和66.1%。无芒雀麦种子以人工分段法收获的效率最高,达到74.7%。高羊茅种子的落粒性较强,联合式收割机收获和人工分段法收获的产量损失均超过50%,应考虑适当提前收获时间。[结论]该研究为当地小规模种植基地与农户分散种植并存的牧草种子生产方式提供技术依据。     

Influence of species, cutting date and cutting interval on the fatty acid composition of grasses

Two experiments were conducted to evaluate the effects of species, cutting date and cutting interval on the concentration of fatty acids in temperate grasses. The first experiment compared eight species, harvested in late autumn and summer. Levels of individual fatty acids were distinctive for some species, with low levels of C18:1 in Dactylis glomerata L. and high levels of C18:2 in Phleum pratense L. Differences in individual fatty acids could not be used to differentiate fescues and ryegrasses. However, fatty acid profiles could be used to differentiate species when material was managed similarly (i.e. at the same cut). There were large species × cut interaction effects, showing that management factors will be as important as plant breeding in manipulating fatty acid levels. Cultivars belonging to one Lolium perenne L. gene pool were identified as having significantly higher α-linolenic acid and total fatty acids in late-season (November) material.
The second experiment compared three ryegrass species over a growing season, with three or five cuts. All species had high concentrations of fatty acids and a high proportion of α-linolenic acid during vegetative growth (late April). Fatty acid levels declined markedly in all species after this date, recovering by autumn. Kunth Lolium multiflorum Lam. and Lolium  ×  boucheanum had higher levels of total fatty acids and α-linolenic acid in the early and late season when compared with perennial ryegrass. Fatty acid levels (particularly C18:2 and C18:3) declined when the regrowth interval was extended from 20 to 38 d.
These studies demonstrate opportunities to change the composition of ruminant products through breeding and management of grasses for altered levels of fatty acids.     

Adaptability and productivity of some warm-season pasture species in a Mediterranean environment

Warm‐season grasses and legumes have the potential to provide forage throughout the Mediterranean summer when there are high temperatures and low rainfall and when cool‐season grasses become less productive. Twenty‐nine non‐native, warm‐season pasture species (twenty‐three grasses and six legumes) were assessed for their adaptability to the coastal plain of southern Italy in terms of their productivity and nutritional quality. The investigated species were compared with two reference species widely used in a Mediterranean environment: a grass (Festuca arundinacea) and a legume (Medicago sativa). The species differed in their phenological and biological characteristics, i.e. start of vegetative resumption, first flowering and cold resistance, from each other and from the control species. From the second year after establishment, warm‐season perennial grasses had high dry‐matter (DM) yields and, in many cases, a more than adequate nutritional quality. As for legumes, the control, M. sativa gave the best results in all the investigated characters. Among the grasses, seven species (Chloris gayana, Eragrostis curvula, Panicum coloratum, Paspalum dilatatum, Pennisetum clandestinum, Sorghum almum, Sorghum spp. hybrid) had DM yields greater than the control species and had their maximum growth during the hottest period of the year, when F. arundinacea, the control grass species, was dormant. Eragrostis curvula had the highest annual DM yield (21·1 t ha^?1) and P. clandestinum provided the best combination of agronomic and yield characteristics which were similar to those of M. sativa. The seven above‐mentioned species have the potential to supply hay or grazing and contribute to broadening and stabilizing the forage production calendar in Mediterranean‐type environments.     

Marandu Palisadegrass Mineral Nutrition and Production Related to Nitrogen and Potassium Supply

Nitrogen (N) and potassium (K) fertilization play a key role in forage crops and can significantly increase yields of ‘Marandu’ palisadegrass [Brachiaria brizantha (Hochst. exA. Rich.) Stapf.], one of the most important forage crops in Brazil. This study aimed to identify the concentrations of total N and K, nitrate (NO₃^?), and ammonium (NH₄⁺), chlorophyll meter readings (SPAD), and nitrate reductase activity (At-RNA) required to maximize yield. Plants were grown in quartz substrate and treated with nutrient solutions that ranged from 2 to 33 mmol L^?1 for N and 0.5 to 11 mmol L^?1 for K. Dry matter production and At-RNA increased with increasing N and K supplies. SPAD readings correlated strongly with N leaf concentration and dry matter production and can be used to assess the N status of this species. The supply of N and K in the fertilization promoted high yield and adequate N and K concentration for plant metabolism.     

Taxonomic relationships and interspecific hybridization in the genus Lolium (grasses)

Phylogenetic trees of the 8 species of the genus Lolium and of Festuca pratensis have been derived from frequency data at 13 isozyme loci using different distance algorithms. The best tree was obtained by the distance-Wagner method with the Cavalli-Sforza and Edwards chord distance. This tree appears robust when tested by bootstrap resampling of loci. This confirmed previous knowledge on species relationships in the genus Lolium, with supplementary data on the taxonomic position of the less studied L. persicum and L. canariense. Attempts were made to hybridize 4 Lolium species and F. pratensis. True interspecific hybrids, as confirmed by isozyme markers, were obtained for L. perenne x L. temulentum, L. temulentum x L. rigidum, L. temulentum x L. canariense and L. canariense x F. pratensis. This is the first report of this new form of Festulolium, which was obtained at a fairly high frequency, giving argument to a possible genetic proximity between L. canariense, an endemic species restricted to Atlantic islands, and F. pratensis, which has a more widespread, northern distribution. However, chromosome pairing analysis at meiosis did not support this conclusion, as the F1 L. canariense x F. pratensis definitely showed a higher level of asynapsis compared to that reported for L. perenne x F. pratensis. The apparently close relation between L. canariense and F. pratensis seen on the tree is therefore postulated to be an artefact, due to the low number of loci studied.