Grass-legume Mixtures Research Articles

Effects of changing simulated sky cover on hyperspectral reflectance measurements for dry matter yield and forage quality prediction

Sensor based analysis methods to assess dry matter yield and nutritive values of legume–grass swards are time and labour saving and can facilitate a site-specific forage management. Nevertheless, in-field measurements, based on canopy reflectance are highly dependent on weather conditions, like, e.g. wind or clouds. This study was conducted to explore the potential of field spectral measurements for a non destructive prediction of dry matter yield (DM), metabolisable energy (ME), ash content (XA), and crude protein (XP), of a binary legume–grass mixture ( Trifolium pratense L. and Lolium multiflorum L.) under changing weather conditions. Five different degrees of sky cover were simulated by shadowing measurement plots with layers of cotton to reduce incoming radiation at different growth stages (leaf developing to flowering). Additionally, a halogen lamp was established over the plots to examine the influence of an artificial light source on the spectral response under changing cloud stages. Modified partial least squares (MPLS) regression was used for analysis of the hyperspectral data set (350–2500 nm). Artificial illumination led to spectral interferences of solar radiation and additional light, and hence, partly reduced prediction accuracies. In contrast, prediction accuracy increased, when solar radiation was completely excluded. Coefficients of determination (RSQ cal) range from 0.87 to 0.94 without artificial illumination and from 0.86 to 0.94 with artificial illumination for DM yield and nutritive values, respectively.

Effect of forage species on fatty acid content and performance of pasture-finished steers

Consumers are increasingly concerned with the form and quantity of fat present in the foods they consume. This is leading to a shift in the way food is produced. In particular the animal industry is increasing the number of organic and naturally finished meat animals rather than finishing them on grains. The objective of this study was to determine if different pasture compositions (i.e. grass only or grass legume mixtures) would impact the fatty acid (FA) meat composition of beef steers (Bos taurus L.). The pasture treatments were tall fescue [Lollium arundinaceum (Schreb.) S.J. Darbysh] only, or tall fescue combined with either red clover (Trifolium pretense L.) or alfalfa (Medicago sativa L. ssp. sativa L.). Beef steers (n=9-10 per treatment) rotationally grazed each pasture treatment. Forage from treatments were different for crude protein (CP), in vitro true digestibility (IVTD) and the FA myristric (C14:0), palmitic (C16:0), palmitoleic (C16:1), stearic (C18:0), oleic (C18:1), linoleic (C18:2), and total FA. Steers grazing mixtures with either red clover (RC) or alfalfa (ALF) had greater average daily gains (ADG) than tall fescue only. Additionally, RC treatment steers had larger ribeye areas (REA) and greater finishing weights than those in the ALF treatment. However, the differences found between pasture treatments in FA concentration did not translate to any differences in the FA concentration of meat harvested from steers. Thus, it is concluded that although the pastures contained different FA concentrations, with the levels of legumes present, this does not influence the FA composition of beef.

Hydrolyzable and fermentable carbohydrates in North Italian pastures for horses

Digestive and metabolic disorders in the horse were previously associated with hydrolyzable and nonhydrolyzable but rapidly fermentable components of nonstructural carbohydrates, particularly fructans. Aim of the study was to assess the contribution of the carbohydrate fractions to the composition of pastures in specific areas of Italy ordinarily designed for horses feeding. Seventy-seven samples from 11 pastures differing for floristic composition were collected across two growing seasons from April 18th2008 to May 10th2009 in the foothills (380 m a.s.l.) of the province of Parma (Italy). All samples were collected during the vegetative growth phase. To identify the bioclimatologic conditions of the growth, the average fortnightly thermohygrometric index (THI) was used. Slow fermentable carbohydrates mean concentration (NDF: 510.6, ADF: 274.7, ADL: 31.5 g/kg DM) reflected the typical chemical composition of high-quality grass and grass-legume mixtures. Among the nonstructual carbohydrates (NSC: 199.9 g/kg DM), hydrlolyzable carbohydrates content accounted for about the 18%. Nonhydrolyzable but rapidly fermentable carbohydrates were constituted for about the 23% by fructans (37.7 g/kg DM, range 15.5 to 138.2). The environmental conditions significantly affected the carbohydrate concentration in forages. Among NSC, fructans concentration in pastures was affected by bioclimatologic conditions (P<0.05). The floristic composition influenced the fructans content at a lesser extent. These results indicate a high variability of fructans concentration and reflect what previously observed in other areas. In any case the high levels observed for fructans in some geographic areas are not been achieved. Further interdisciplinary studies in this area between veterinarians and forage researchers are clearly warranted.

Mitigating the greenhouse gas balance of ruminant production systems through carbon sequestration in grasslands

Soil carbon sequestration (enhanced sinks) is the mechanism responsible for most of the greenhouse gas (GHG) mitigation potential in the agriculture sector. Carbon sequestration in grasslands can be determined directly by measuring changes in soil organic carbon (SOC) stocks and indirectly by measuring the net balance of C fluxes. A literature search shows that grassland C sequestration reaches on average 5 ± 30 g C/m2 per year according to inventories of SOC stocks and −231 and 77 g C/m2 per year for drained organic and mineral soils, respectively, according to C flux balance. Off-site C sequestration occurs whenever more manure C is produced by than returned to a grassland plot. The sum of on- and off-site C sequestration reaches 129, 98 and 71 g C/m2 per year for grazed, cut and mixed European grasslands on mineral soils, respectively, however with high uncertainty. A range of management practices reduce C losses and increase C sequestration: (i) avoiding soil tillage and the conversion of grasslands to arable use, (ii) moderately intensifying nutrient-poor permanent grasslands, (iii) using light grazing instead of heavy grazing, (iv) increasing the duration of grass leys; (v) converting grass leys to grass-legume mixtures or to permanent grasslands. With nine European sites, direct emissions of N2O from soil and of CH4 from enteric fermentation at grazing, expressed in CO2 equivalents, compensated 10% and 34% of the on-site grassland C sequestration, respectively. Digestion inside the barn of the harvested herbage leads to further emissions of CH4 and N2O by the production systems, which were estimated at 130 g CO2 equivalents/m2 per year. The net balance of on- and off-site C sequestration, CH4 and N2O emissions reached 38 g CO2 equivalents/m2 per year, indicating a non-significant net sink activity. This net balance was, however, negative for intensively managed cut sites indicating a source to the atmosphere. In conclusion, this review confirms that grassland C sequestration has a strong potential to partly mitigate the GHG balance of ruminant production systems. However, as soil C sequestration is both reversible and vulnerable to disturbance, biodiversity loss and climate change, CH4 and N2O emissions from the livestock sector need to be reduced and current SOC stocks preserved.

Current and Potential Development of Perennial Grasses in Rainfed Mediterranean Farming Systems

ABSTRACTPast and recent development of perennial grasses in the rainfed Euro‐Mediterranean region is reviewed concerning climatic constraints and main types of farming systems. The few Mediterranean cultivars that are registered and available are used for livestock production and cover crops only in subtemperate areas. These cultivars are adapted where annual rainfall exceeds 500 mm and accumulated water deficit from May to September is &lt;800 mm. For the future, grass–legume mixtures need to be developed to meet the contrasting situations of livestock production and environmental use, with both functions contributing to farm income through the market and from public subsidies. Concern for environmental uses of perennial grasses raises interest in new germplasm that could accelerate cultivar breeding and seed production. Research programs should ensure a diversification of available germplasm in the principal forage species for phenology, drought tolerance, summer dormancy levels, and dehydration tolerance.

Determining the Contribution of Legumes in Legume–Grass Mixtures Using Digital Image Analysis

ABSTRACTDigital image analysis could be a rapid and precise technique for estimating legume proportions in grass swards. In 2004, we conducted a pot study to evaluate a digital image analysis (DIA) system for estimation of legume dry matter (DM) contribution in legume–grass mixtures. Examination of pure swards and binary legume–grass mixtures of red clover (Trifolium pratense L.), white clover (T. repens L.), alfalfa (Medicago sativa L.), and perennial ryegrass (Lolium perenne L.) took place after 35, 49, and 63 d of growth. To estimate the cover percentage of legumes in the swards, a total of 64 digital pictures were taken. The DM contribution of legumes (% of total biomass) showed a significant relationship with the proportion of image area covered by legumes (% of total area), which was classified visually. A DIA system for grayscale images was developed with the software Optimas. We found that DIA could be used to accurately predict legume contribution in mature swards. Legume contribution, as estimated by DIA, was significantly correlated with DM contribution of red clover (R2 = 0.87), white clover (R2 = 0.85), and alfalfa (R2 = 0.79). Bare ground reduced the predictive ability of DIA in young or open swards. Use of DIA may be limited until we refine the method to deal with bare ground and different leaf shapes associated with various weed species.

Development of Canopy Reflectance Models to Predict Forage Quality of Legume–Grass Mixtures

ABSTRACTTimely assessments of nutritive values of legume‐based swards during the growing season can facilitate a targeted and site‐specific forage management. This study was undertaken to explore the potential of field spectral measurements for a nondestructive prediction of metabolizable energy, ash content, crude protein (CP), and acid detergent fiber of legume–grass mixtures. A population of 200 legume–grass swards (Lolium perenne L., Trifolium repens L., Trifolium pratense L.) representing a wide range of legume proportion (0–100% of dry matter), and growth stages (beginning of tillering to end of flowering) were used in this investigation. The paper examines three techniques for analysis of the hyperspectral data set (350–2500 nm): two‐waveband reflectance ratios, modified partial least squares (MPLS) regression, and stepwise multiple linear regression (SMLR). Forage quality variables had weak relationships with the developed reflectance ratios, whereas hyperspectral analysis by MPLS and SMLR resulted in high precision (0.70 ≤ R2 ≤ 0.94). Even with a reduced spectral data set (630–1000 nm), estimates of MPLS and SMLR models were still acceptable for forage ash (0.62 ≤ R2 ≤ 0.78) and CP (0.83 ≤ R2 ≤ 0.86), a finding that could facilitate an application of field spectroscopy with more simple sensors. Estimates of ash and CP were further improved by legume‐specific calibrations.

Determination of Dry Matter Yield from Legume–Grass Swards by Field Spectroscopy

ABSTRACTAn efficient and accurate detection of dry matter (DM) yield of legume–grass mixtures can facilitate a targeted and site‐specific management of legume‐based swards. The major objective of this study was to examine the relationship between spectral signatures of legume–grass swards and DM yield across a wide range of legume species (white clover [Trifolium repens L.], red clover [T. pratense L.], alfalfa [Medicago sativa L.], birdsfoot trefoil [Lotus corniculatus L.]), legume proportion (0–100% of DM), and growth stage (beginning of tillering to end of flowering). Modified partial least squares (MPLS) regression, stepwise multiple linear regression (SMLR), and the vegetation indices (VIs), simple ratio, normalized difference vegetation index, enhanced vegetation index, and red edge position were used for analysis of the hyperspectral data set (350–2500 nm). Compared to common calibrations, legume‐specific models achieved better results, indicating that each legume species had its own spectral characteristics. Modified partial least squares and SMLR gave the best R2 values, ranging in cross validation from 0.74 to 0.92 with a standard error below 92 g DM m−2 The DM yield prediction by VIs resulted in unsatisfactory accuracies. Prediction accuracy for MPLS and SMLR models were still acceptable even with a reduced spectral data set (630–1000 nm), a finding that could facilitate an application of field spectroscopy in practice.

Strong mixture effects among four species in fertilized agricultural grassland led to persistent and consistent transgressive overyielding

SummaryIncreasing plant species richness often increases biomass production in nutrient‐poor semi‐natural grasslands. If such positive diversity–productivity effects also apply to nutrient‐rich agricultural grasslands, mixtures could improve resource‐use efficiency in the vast area used for forage production. We therefore quantified the diversity–productivity effects in nutrient‐rich agricultural grasslands using four‐species grass–legume mixtures.The sown overall density and species proportions ofLolium perenne,Dactylis glomerata,Trifolium pratenseandTrifolium repenswere varied in a 3‐year field experiment to investigate the effects of species richness (1, 2, 4 species) and species proportion (0, 3, 10, 25, 40, 50, 70, 90, 100% sowing proportion) on productivity under a nitrogen fertilization of 50, 150 or 450 kg N ha−1 year−1.The four‐species mixtures reached up to twice the yield of the average of the four species’ monocultures (overyielding up to 106%), predominantly due to combining grass and legume species. Mixtures were up to 57% more productive than the most productive monoculture (transgressive overyielding). Both these diversity–productivity effects appeared across a broad range of species proportions and persisted at the two lower levels of N fertilization for 3 years.Mixtures fertilized with 50 kg N ha−1 year−1produced yields comparable to grass monocultures fertilized with 450 kg N ha−1 year−1, if the legume proportion was about 50 to 70%. Diversity–productivity effects were reduced at the highest level of N fertilization, where they virtually disappeared in the third year. Increased N fertilization also accelerated the observed general trend towardsD. glomeratadominated and legume‐poor swards.Synthesis and applications. Diversity–productivity effects led to consistent transgressive overyielding in intensively managed grasslands, suggesting a highly increased resource‐use efficiency in mixtures. Performance better than monocultures can be achieved with grass–legume mixtures that have a low number of species, across a wide range of species proportions and in nutrient‐rich conditions. Processes such as niche complementarity and positive interspecific interactions leading to diversity effects proved to be highly relevant and widely applicable for intensive forage production. Such diversity–productivity effects could allow reduced inputs of N fertilizer without loss of productivity in different grassland production systems.

Grazing Schedule Effect on Forage Production and Nutritive Value of Diverse Forage Mixtures

The use of complex mixtures (mixtures of more than three species) may increase yield of pastures; however, we know little about how grazing management affects the productivity of mixtures. A grazing experiment was performed during 2005 and 2006 near State College, PA, to compare mixtures of grasses, legumes, and chicory (Cichorium intybus L.) for their botanical composition, nutritive value, and forage production under two grazing schedules: when the sward reached 25 cm in height (sward height schedule, SH) or when alfalfa (Medicago sativa L.) reached the bud stage (morphology or MP schedule). The SH schedule produced 30% more dry matter (DM) than the MP schedule averaged for 2 yr. Forage yield of the five‐species (6427 kg ha−1 in 2005 and 6624 kg ha−1 in 2006) and seven‐species (6816 kg ha−1 in 2005 and 6772 kg ha−1 in 2006) mixtures was stable during the contrasting weather of 2005 and 2006. Grass monoculture with N and simple mixtures (two species, grass–legume) produced 989 kg ha−1 more DM than the complex mixtures in 2006 when weather conditions were favorable. The SH schedule produced forage of better nutritive value compared with the MP schedule at first harvest in both years [20 g kg−1 less acid detergent fiber (ADF) in 2006; 25 g kg−1 in 2005, 53 g kg−1 in 2006 more neutral detergent fiber (NDF); 21 g kg−1 in 2005, 30 g kg−1 in 2006 more crude protein (CP); and 33 g kg−1 in 2006, 53 g kg−1 more in vitro true dry matter digestibility (IVTDMD)]. Complex mixtures of forage species provide more consistent yields of DM than binary grass–legume mixtures or grass monocultures in variable environments.

Impact of Available Nitrogen in Mine Site Revegetation: A Case Study in the Coeur d'Alene (Idaho) Mining District

A variety of soil amendments were evaluated for suitability in revegetation of waste rock piles in the Coeur d'Alene Mining District of northern Idaho. The amendments included biosolids, composts, log yard wastes, and two liquid‐based organic treatments. Initial available nitrogen (N) (ammonia plus nitrate) values varied significantly with the type of amendment, ranging from 20 lb/ac in the liquid‐based soil treatments to 2800 kg/ha in a biosolids treatment. As would be expected, high available N increased the potential for high runoff N. The level of available N also had a strong impact on plant frequency vs. density, species distribution, and the extent of unseeded vegetation. For example, high N amendments promoted a high‐frequency/low‐density vegetation profile that was dominated by grass species and contained low content of unseeded vegetation. Conversely, the low N amendments promoted a low‐frequency/high‐density profile with a diverse grass–legume mixture but also a greater density of weeds.

Prediction of yield and the contribution of legumes in legume-grass mixtures using field spectrometry

Productivity and botanical composition of legume-grass swards in rotation systems are important factors for successful arable farming in both organic and conventional farming systems. As these attributes vary considerably within a field, a non-destructive method of detection while doing other tasks would facilitate more targeted management of crops and nutrients in the soil–plant–animal system. Two pot experiments were conducted to examine the potential of field spectroscopy to assess total biomass and the proportions of legume, using binary mixtures and pure swards of grass and legumes. The spectral reflectance of swards was measured under artificial light conditions at a sward age ranging from 21 to 70 days. Total biomass was determined by modified partial least squares (MPLS) regression, stepwise multiple linear regression (SMLR) and the vegetation indices (VIs) simple ratio (SR), normalized difference vegetation index (NDVI), enhanced vegetation index (EVI) and red edge position (REP). Modified partial least squares and SMLR gave the largest R 2 values ranging from 0.85 to 0.99. Total biomass prediction by VIs resulted in R 2 values of 0.87–0.90 for swards with large leaf to stem ratios; the greatest accuracy was for EVI. For more mature and open swards VI-based detection of biomass was not possible. The contribution of legumes to the sward could be determined at a constant biomass level by the VIs, but this was not possible when the level of biomass varied.

Utilization of Kura Clover-Reed Canarygrass Silage Versus Alfalfa Silage by Lactating Dairy Cows

The mixture of kura clover (Trifolium ambiguum M. Bieb.) and reed canarygrass (Phalaris arundinacea L.) has proven to be extremely persistent in the northern United States, but information about dairy cow performance on this mixture is lacking. Twenty lactating Holstein cows were used in a crossover design to compare dry matter (DM) intake and milk production from diets containing kura clover-reed canarygrass silage (KRS) or alfalfa (Medicago sativa L.) silage (AS). Forages were cut, wilted, ensiled in horizontal plastic bags, and allowed to ferment for at least 50 d before beginning the feeding experiment. The KRS was approximately 40% kura clover and 60% reed canarygrass. Treatments were total mixed rations formulated with either 57% of total DM from 1) AS or 2) KRS. Experimental periods were 28 d, with the first 14 d for diet adaptation and the last 14 d for measurement of intake and milk production. The neutral detergent fiber (NDF) concentrations of AS and KRS were 37.3 and 47.3%, respectively. The fermentation analyses indicated that both silages underwent a restricted fermentation, producing primarily lactic acid and some acetic acid. Dry matter intake (24.2 vs. 22.8kg) and 4% fat-corrected milk (32.8 vs. 30.9kg) were significantly higher for cows fed AS than for cows fed KRS. Cows consumed less NDF (6.7 vs. 8.0kg) and less digestible NDF (3.0 vs. 4.4kg) when fed AS diets compared with KRS diets, but the pool of ruminally undegraded NDF was similar (3.7kg) between diets. Cows produced 1.5kg of milk/kg of DM consumed regardless of the diet, indicating that digestible NDF of KRS was utilized with similar efficiency as the cell wall constituents of AS, but the intake of cows fed KRS may have been limited by rumen fill. Milk fat concentration tended to be higher for cows fed AS, but the milk true protein concentration and yields of fat and protein did not differ by treatment. Milk urea nitrogen content was higher when cows consumed AS (16.4mg/ dL) compared with KRS (13.4mg/dL). The cows fed KRS consumed more NDF but less total DMI, based on the results from this trial with diets formulated to contain approximately 60% of DM as forage, resulting in slightly lower milk yields than cows fed excellent-quality AS. This grass-legume mixture has the potential to be a source of quality forage for dairy cows in regions where alfalfa persistence is a problem.

The Effect of Variable Seed Rate Proportions on Agronomic Attributes, Dry Matter Production, Biological Potential and Economic Viability of Some Grass-Legume Mixed Pastures

An experiment was conducted to assess the agronomic attributes, dry matter (DM) yield, biological potential and economic viability of grass-legume mixtures at Haramaya University in Ethiopia during 2004 and 2005. Chloris gayana, Panicum coloratum, Melilotus alba and Medicago sativa were planted as pure stand and in mixtures using 50:50, 33: 67, 67: 33, 25: 75 and 75: 25 seed rate proportion to give 24 treatments in a randomised complete block design with 3 replications. There were significant (P < 0.05) differences in the number of seedlings per m2 (SLM), row cover, number of tillers per m2, days to 50% flowering (DF 50%) of the grass components among the grass/legume combinations due to seed rate proportions. Moreover, SLM, the number of branches per m2, the height of the plant at harvest, DF 50% of the legume components were significantly (P < 0.05) affected among the mixtures due to seed rate proportions. There was a significant (P < 0.05) difference in the DM yield of pure stand grasses and legumes, and their mixtures due to seed rate proportion. Significant (P < 0.05) effects were also observed on the relative yield (RY), the relative total yield (RTY), the relative crowding coefficient (RCC) and the aggressivity index of both the grass and legume components and their mixtures due to different seed rate proportions throughout the study. The two years\' mean RTY of all grass-legume mixtures were greater than one (range: 1.23-2.11) and Chloris mixed with Melilotus and Medicago with 67: 33 seed rate proportion had higher RTY than other mixtures. Both the grass and legume components in the mixture produced mean RCCs values in excess of unity and almost equal values in both components, indicating that all yielded better in the mixture than expected in pure stands at different seed rates. Chloris gayana mixed with Melilotus alba at 50:50 and 33:67 seed rate proportion gave higher DM yield, average net return/ha and average net return/ha/yr compared to pure stand grasses and legumes and their different mixtures during the study. Therefore, to alleviate the feed scarcity in the area; these grass-legume mixtures could be introduced to smallholder farms. In addition, further studies on animal performances should be conducted using feeding trials and under grazing conditions. Keywords: Agronomic Attributes; Biological Potential; Dry Matter Yield; Economic Viability; Grass/Legume Mixture; Seed Rate Proportion East African Journal of Sciences Vol. 2 (2) 2008: pp. 95-104

Effect of supplementation of Sesbania sesban to lactating ewes on milk yield and growth rate of lambs

The present experiment was conducted to study the effects of supplementation of Sesbania sesban on the milk yield of ewes and growth rate of their lambs. The experiment was done with animals that had been fed for 16 months on a basal diet of teff straw supplemented with concentrates alone (0% S. sesban) or 95% of supplementary protein provided by S. sesban (accession 15019). Thirty lactating ewes and their single lambs of Ethiopian highland Menz sheep were used in this study. The post partum weight of ewes and birth weight of their lambs ranged between 16–22 kg and 1.3–2.4 kg. The ewes continued to be fed a teff straw basal diet and supplemented with two levels of S. sesban (0, and 95% of supplementary protein provided by S. sesban and the rest being provided by concentrates) for 3 months. Three weeks after birth lambs were offered a succulent green grass–legume mixture ad libitum. Dry matter and organic matter intake of basal feed and total feed, live weight at weaning and post partum daily body weight gain of ewes were not significantly different ( P > 0.05) between treatments. The milk yield of ewes was significantly affected ( P < 0.05) by dietary treatments. Ewes supplemented with S. sesban showed a 13% increase in milk production over ewes supplemented with concentrates. The peak lactation for ewes supplemented with S. sesban was higher and persisted longer than for ewes supplemented with concentrates. Lambs born from ewes supplemented with S. sesban had a significantly higher pre-weaning growth rate and were heavier at weaning ( P < 0.05) than lambs born from ewes supplemented with concentrates. We concluded that supplementation of S. sesban at 30% of the ration (0.98% of their body weight) during lactation improved milk yield of ewes and growth rate of lambs.

Yield and Species Composition of Binary Mixtures of Kura Clover with Kentucky Bluegrass, Orchardgrass, or Smooth Bromegrass

Kura clover (Trifolium ambiguum M. Bieb.) is a rhizomatous perennial legume that has potential as a forage crop in the North-Central USA because of its excellent persistence under environmental extremes. Little information is available about defoliation effects on productivity of mixtures of kura clover with grasses typically grown in this region. Two field trials were conducted to evaluate the effects of defoliation management on yield and species composition of binary mixtures of 'Rhizo' kura clover with 'Comet' orchardgrass (Dactylis glomerata L.), 'Badger' smooth bromegrass (Bromus inermis Leyss.), 'Park' Kentucky bluegrass (Poa pratensis L.), and solo-seeded kura clover near Arlington, WI. Three harvest schedules (three, four, or five times annually) and two cutting heights (4 or 10 cm) were imposed. Infrequent defoliation and lower cutting height produced significantly greater total forage yield, 6.6, 5.8, and 5.2 Mg/ha in 3-, 4-, and 5-harvest systems, respectively; and 6.5 and 5.2 Mg/ha for the 4- and 10-cm cutting height, respectively. Averaged over 3 yr and two environments, mixtures had higher forage productions than solo kura clover (6.3, 5.7, and 6.0 Mg/ha for the Kentucky bluegrass, orchardgrass, and smooth bromegrass mixtures, respectively; compared to 5.2 Mg/ha for solo kura clover). The proportion of kura clover in mixtures increased from yr 1 to yr 2 and was constant from yr 2 to yr 3 (34, 58, and 57%, respectively). We conclude that kura clover has excellent potential as a long-term component of grass-legume mixtures regardless of the cutting height, harvest frequency or grass species, even though the proportion of kura clover in harvested forage was significantly greater with less frequent harvest and shorter cutting height of all mixtures.

Nitrates in plants and soil after fertilization of grass-legume mixtures

Nitrates are one of the most frequent utilized forms of N from soil. Through root they reach stem and leaf where in photosynthetic processes they convert into proteins. Due to exposure to stress situations, and excessive nitrogen fertilization, nitrate accumulation in plant tissues and organs occurs. Also, nitrates can accumulate in harmful concentrations in soil. Nitrates accumulated in plants have harmful effect on animals which consume plants since they cause various health disorders. In variance analysis in both investigation years it was established that fertilization as well as interaction of factors mixture/fertilization had very significant effect on investigated quality parameter, contrary to mixture as single factor. In both investigation years, treatments with 210 kgN ha-1 had the highest nitrate concentration. Content of nitrate nitrogen in soil is increased by fertilization. Objective of the research was to determine nitrate quantities which are accumulated in plants subsequent to n fertilization and growing in mixtures with other species, as well as to determine nitrate quantities which remain in the soil unutilized, which are potential causes of environment pollution.

Combining Ability of Binary Mixtures of Introduced, Cool‐ and Warm‐Season Grasses and Legumes

When two forage species are grown together they can be compatible, compete, or allelopathic with each other. We estimated the combining ability effects for introduced, cool‐ (CS) and warm‐season (WS) grasses and legumes grown in binary mixtures. Six pure stands and 15 mixtures were transplanted into field plots in a replicated randomized block design at Woodward, OK. Plots were harvested three times a year over a 2 yr period. Each harvest was analyzed as a mixed model combining ability analysis. The dependent variables were forage dry matter (DM) and crude protein (CP) yield. Specific combining ability (SCA) effects for DM yield were either zero or negative for mixtures of CS grasses or mixtures of WS grasses. For DM yield the SCA effects were either zero or positive for CS grass‐legume mixtures or zero or negative for WS grass‐legume mixtures. A few grass–grass and grass–legume mixtures produced positive SCA effects; but, their species compositions were highly skewed toward one species. When SCA effects are zero, species compete with each other. This was the case for yellow bluestem [Bothriochloa ischaemum (L.) Keng. var. ischaemum (Hack.) Celarier and Harlan]–legume mixtures. Yellow bluestem‐legume mixtures averaged 59% yellow bluestem: 41% legume DM forage across harvests. Yellow bluestem‐legume mixtures may be a suitable forage production system for the Southern Plains. Long‐term grazing studies are needed to determine the sustainability of these mixtures.

Performance of Grass-Legume Mixtures under Irrigation in the Southeastern Anatolia Region of Turkey

Performance of Grass-Legume Mixtures under Irrigation in the Southeastern Anatolia Region of Turkey

Formation of the productivity of a legume-grass mixture under conditions of agrolandscapes in the central region of the non-Chernozem Zone of the Russian federation

The landscape approach to developing perennial grass cultivation practices made it possible to reveal ecologically homogeneous sections and to create the basis for organizing sustainable fodder production under the complex landscape conditions of the region. The adaptation characteristics of perennial grasses and their productivity are different in agromicrolandscapes characterized by the same geochemical association of relief features but on different hill slopes (southern and northern).