Herbage Dry Matter Yield Research Articles

Seasonal nitrogen effects on nutritive value in binary mixtures of tall fescue and bermudagrass

AbstractThe addition of cool‐season, tall fescue [Lolium arundinaceum (Schreb.) Darbysh.], to warm‐season, bermudagrass [Cynodon dactylon (L.) Pers.], pastures can improve forage productivity and nutritive value. Effects of four binary mixtures consisting of cv. Flecha (incompletely summer dormant) and cv. Jesup (summer active) tall fescue overseeded into established stands of cv. Russell and cv. Tifton 44 bermudagrass and three seasonal N treatments were evaluated on dry‐matter (DM) yield, crude protein (CP), in vitro true digestible DM (IVTDDM), acid detergent fibre (ADF) and neutral detergent fibre (NDF). Nitrogen‐timing treatments were 168 kg N ha−1 (as ammonium nitrate) split into three applications per season with an additional 8·6 t ha−1 of broiler litter (as‐is moisture basis) split into two applications varied to favour either tall fescue (in October and January), bermudagrass (in March and May) or both grasses (in January and March). Treatment effects were determined in samples of mixed herbage harvested in April, May, July, August and September of 2009 and 2010. Regardless of bermudagrass cultivar, herbage DM yield was greater (P < 0·05) in Flecha–bermudagrass than Jesup–bermudagrass in July of both years and in August 2010. Nutritive value generally was greatest in Jesup–Tifton 44, based on high CP and IVTDDM, and low ADF and NDF. Averaged across mixtures, avoiding fertilizer N and litter applications beyond April increased (P < 0·01) DM yield in April and May and IVTDDM in July (603 vs. 629 g kg−1; 2‐year average) and August (618 vs. 660 g kg−1) compared with applications in January–July. The timing of N and broiler litter applications on tall fescue–bermudagrass to favour growth of tall fescue appeared to increase fescue cover during the cool season and nutritive value of the mixed herbage during the warm season.

Establishment‐Year Native Perennial Bunchgrass Biomass Yields

Weak seedling vigor of native North American perennial bunchgrasses may result in poor establishment‐season herbage dry matter (DM) yields (HY). Interseeding North American annual legumes as an N source during grassland restoration, pasture establishment, or bioenergy crop seeding might compound this limitation. Our first objective was to evaluate yellow Indiangrass [Sorghastrum nutans (L.) Nash], switchgrass (Panicum virgatum L.), and little bluestem [Schizachyrium scoparium (Michx.) Nash] first‐season HY in the southern Great Plains of North America. This took place in north–central Texas on a Windthorst fine sandy loam soil with no irrigation or soil amendments. Our second objective was to measure the effects of cross‐drilling native North American annual legumes smooth‐seeded wild bean [Strophostyles leiosperma (Torr. & Gray) Piper], trailing wild bean [Strophostyles helvula (L.) Elliott], and showy partridge pea [Chamaecrista fasciculata (Michx.) Greene] on bunchgrass first‐season HY. In the drier (340 mm) year, legumes failed to establish, while switchgrass produced 2410 and Indiangrass yielded 1980 kg HY ha−1 y−1. In the year with 687 mm rainfall, legumes had no negative effects (P > 0.05) on grass HY (5490 kg HY ha−1 y−1 for switchgrass) despite providing up to 49 through 1800 kg HY ha−1 y−1 (showy partridge‐pea with little bluestem; P ≤ 0.05 for year by grass × legume interactions). Our results indicate that these bunchgrasses produced harvestable HY during their establishment year and that simultaneously seeding annual legumes did not impair native perennial grass establishment while, in 1 yr, making potential N contributions for subsequent stand productivity.

Small Grain Cereal–Clover Mixtures for Forage Production

Abstract Fresh forages are the cheapest source of animal feed in world. Small grain cereals (SGC) are the most commonly used fresh forages or ensiled forage. Clovers are the perennial legumes that offer quality forage but their initial dry matter (DM) yield is low. Usually, SGC and clover are sown in mixtures to draw benefits from greater Cut-1 DM yield of cereals and biological nitrogen (N) fixation of clovers. However, mixtures are difficult to manage, compared to monoculture owing to differences in their growth pattern, temporal, spatial and physical requirements. In this review, SGC-clover mixtures are analyzed for their potential herbage DM yield and quality of the produce. Effect of various management factors on the productivity of forage mixtures are well documented. Decisions in managing mixtures, like choice of cereal and cutting time and how they affect the value of the final produce is reviewed. Besides decision, effect of relative proportion and spatial arrangement of intercrops is also deliberated. Special attention is paid to the competition between SGC and clovers and its impact on clover suppression in mixture. At the end conclusions are drawn to optimize production from mixtures.

Simulation of herbage yield and growth components of Cock’s foot (Dactylis glomerata L.) in Jablje using the calibrated LINGRA-N model

In the study the previously calibrated LINGRA-N model was used for a long term simulation (1964–2013) of the herbage dry matter yield (GRASS) and growth analysis of Cock’s foot (Dactylis glomerata L.) in Jablje. Changes in the yearly GRASS variability are reflected in the appearance of outliers in the second half of the study period. The biggest reductions in GRASS are seen in the years 1992, 1993 and 2003. These are the driest years according to meteorological variables (high maximum and minimum air temp eratures, low precipitation) and also according to the simulations, with the lowest reduction factor for crop growth due to drought. The potential yield (YIELD) is not linearly dependent on meteorological variables. Some growth compone nts were compared on a daily basis in a dry year (1993) and an average year (1994). In 1993, for instance, 53 % of photosynth etically active radiation was intercepted, against 75 % in 1994. Seasonal development of the actual soil moisture content was linked to the development of the leaf area index and consequently to the mass of green leaves, to the roots mass, to the mass of dead leaves and to GRASS. The results highlight the need for further research, on field and with simulations. As re gards the latter, we have to keep in mind that they inevitably involve various uncertainties.

Calibration of the LINGRA-N model to simulate herbage yield of grass monocultures and permanent grassland in Slovenia

In this study, we calibrated the LINGRA-N model using the minimization of RMSE, and proceeded to evaluate its performance. We simulated herbage dry matter yield of cock's foot (Dactylis glomerata L.) and perennial ryegrass (Lolium perenne L.) in Jablje in the period 1998–2013, and multiplespecies grassland in Ljubljana (S72) in 1974–1993. The overall performance of LINGRA-N is fair for perennial ryegrass (RMSE% < 25%) and good for cock’s foot and S72 (RMSE% < 15%). The index of agreement (d) suggests that LINGRA-N is not calibrated well enough to simulate the interannual herbage yield variability for S72, so the model cannot yet be used for the simulation of multi-species grassland herbage yield. In contrast, the herbage yields of cock’s foot and perennial ryegrass in Jablje are simulated correctly (with d values 0.84 and 0.78, respectively). One of our further goals is to use the calibrated model on a specific location for the simulation of the herbage yield of grass monocultures under various weather conditions as well as for the simulation of climate change effect on it.

Comparisons of biological nitrogen fixation in association with white clover (Trifolium repens L.) under four fertiliser nitrogen inputs as measured using two 15N techniques

The objectives of this study were to compare techniques for measuring biological nitrogen fixation (BNF) and to assess how fertiliser N input affects the balance between BNF and sustainable herbage production on perennial ryegrass (Lolium perenne L.)/white clover (Trifolium repens L.) grassland. Biological N fixation and herbage production by white clover based grassland was measured in 2011 and 2012 under four nominal annual fertiliser N inputs: 0 (0N), 86 (86N), 140 (140N) and 280 kg ha−1 (280N). Biological N fixation was measured using the 15N isotope dilution and 15N natural abundance techniques under all fertiliser N inputs and also using the nitrogen difference technique under 0N. The two 15N techniques produced similar annual estimates of above-ground BNF across the range of fertiliser N inputs. Fertiliser N input resulted in higher herbage dry matter yield, but reduced annual BNF which averaged 80, 64, 66 and 47 kg ha−1 on 0N, 86N, 140N and 280N, respectively, across both techniques and years. The two 15N techniques were comparable in estimating BNF. Intermediate fertiliser N inputs achieved a balance between minimising detrimental impact on BNF and potential N loss while producing more herbage DM yield than clover swards receiving no fertiliser N.

Effects of low precipitation periods on the herbage yield of mesic semi-natural grasslands under different cutting regimes

Climatic changes have led to extreme weather events, with longer dry periods affecting forage production in mesic grasslands. The effects of grassland management and years with periods of low precipitation on herbage dry matter (DM) yield were studied in two-long term grassland experiments with different cutting and fertilization regimes for the period 2000–2012. In both experiments, the annual herbage DM yields had high correlations with the amount of precipitation. The correlation was stronger in frequent cuttings regimes. The management type and the year significantly affected the herbage DM yield in both experiments. There was also a significant management × year interaction. On average, over the whole observation period, the herbage DM yield of equally fertilized treatments in experiment I was higher in treatments with two cuts per season than in treatments with more cuts. Furthermore, longer periods of low precipitation exerted fewer effects on the DM yield of the two cuts treatments compared to higher cutting frequencies. However, the increase in herbage productivity in years following seasons with low precipitation was higher in the treatments with higher cutting frequencies than in those with two cuts per season. When the treatment, cut four times per year, received a higher amount of fertilizer than the treatment, cut twice per year (experiment II), the long-term average annual herbage DM yield was higher and the yield was less decreased by longer periods of low precipitation than the two cuts per year treatment. Despite the fact that the effects of different treatments were proved in both experiments, the differences in the DM yields among the treatments in low precipitation years were not high enough to recommend best-management practices for forage production on mesic grasslands in areas subject to increasing periods of low precipitation.

Effect of age of regrowth on yield and herbage quality of Panicum coloratum under sub humid climatic conditions of Ethiopia

The effect of stage of harvest on dry matter (DM) yield and herbage nutritive value of Panicum coloratum under sub humid climatic conditions of western Ethiopia was evaluated. Three harvesting stage treatments (8, 10 and 12 weeks of regrowth age) were assessed. The herbage DM yield (P<0.05); and leaf (P<0.05) and stem component DM yields (P<0.01); and leaf to stem ratio (P<0.001) values were significantly affected by the age of regrowth. Herbage and stem component DM yields; and stand density exhibited an increasing trend with age of regrowth. Mean herbage DM yield ranged from 11.04±0.91tha-1 to 14.71±0.91tha-1. The crude protein (CP) content was 8.28±0.34 and 8.43±0.34% for the 8 and 10 weeks treatments, respectively, while it declined to 6.27±0.34% for samples harvested at 12 weeks of age. Mean values of neutral detergent fibre (NDF) were generally high for all harvesting treatments, the values ranging from 74.02±0.85 to 77.50±0.85%. The in vitro DM digestibility (IVDMD) values ranged from 46.92% for the 12 weeks to 53.65% for the 8 week harvests. The calcium concentration ranged from 0.38±0.05% for the 10 weeks treatment to 0.51±0.05% for that of 10 weeks. Similarly, phosphorus content varied from 0.13±0.005 to 0.15±0.005% and no clear trend was observed with stage of maturity. It was recommended that the grass be harvested at 8 weeks of regrowth age for optimal yield and quality. Key words: Dry matter yield, leaf to stem ratio, crude protein, neutral detergent fibre, in vitro dry matter digestibility, calcium, potassium.

Leaf Rubisco turnover in a perennial ryegrass (Lolium perenne L.) mapping population: genetic variation, identification of associated QTL, and correlation with plant morphology and yield

This study tested the hypotheses that: (i) genetic variation in Rubisco turnover may exist in perennial ryegrass (Lolium perenne L.); (ii) such variation might affect nitrogen use efficiency and plant yield; and (iii) genetic control of Rubisco turnover might be amenable to identification by quantitative trait loci (QTL) mapping. A set of 135 full-sib F1 perennial ryegrass plants derived from a pair cross between genotypes from the cultivars 'Grasslands Impact' and 'Grasslands Samson' was studied to test these hypotheses. Leaf Rubisco concentration at different leaf ages was measured and modelled as a log-normal curve described by three mathematical parameters: D (peak Rubisco concentration), G (time of D), and F (curve standard deviation). Herbage dry matter (DM) yield and morphological traits (tiller weight (TW), tiller number (TN), leaf lamina length (LL), and an index of competitive ability (PI)) were also measured. The progeny exhibited continuous variation for all traits. Simple correlation and principal component analyses indicated that plant productivity was associated with peak Rubisco concentration and not Rubisco turnover. Lower DM was associated with higher leaf Rubisco concentration indicating that Rubisco turnover effects on plant productivity may relate to energy cost of Rubisco synthesis rather than photosynthetic capacity. QTL detection by a multiple QTL model identified seven significant QTL for Rubisco turnover and nine QTL for DM and morphological traits. An indication of the genetic interdependence of DM and the measures of Rubisco turnover was the support interval overlap involving QTL for D and QTL for TN on linkage group 5 in a cluster involving QTL for DM and PI. In this region, alleles associated with increased TN, DM, and PI were associated with decreased D, indicating that this region may regulate Rubisco concentration and plant productivity via increased tillering. A second cluster involving QTL for LL, TN, PI and DM was found on linkage group 2. The two clusters represent marker-trait associations that might be useful for marker-assisted plant breeding applications. In silico comparative analysis indicated conservation of the genetic loci controlling Rubisco concentration in perennial ryegrass and rice.

Effect of Harvesting Gliricidia Sepium at Different Cutting Frequencies on Quantity and Quality of Herbage Biomass for Dairy Cattle Nutrition.

Herbage quantity and quality response of Gliricidia sepium to pruning intervals (1.0 to 6.0 months) was evaluated. Chemical composition of coppice re-growth was estimated and herbage was incubated in three rumen fistulated Friesian steers for 3, 6, 12, 24, 48, 72, 96 and 120 h. Herbage dry matter yield tended to follow linear response (P= 0.0689) with increasing coppice re-growth maturity and ranged between 36.2 tones/ha/year to 49.1 tones/ha/year. Protein content (291 g/ kg DM to 220 g/kg DM) decreased following a quadratic trend. However, fibre content increased following a curvilinear trend as herbage matured but levels of lignification increased linearly with delayed harvesting. Additionally, fraction ‘b’ of dry matter degradability (548 to 716 g/kg DM) decreased linearly with herbage maturity. Herbage potential degradability (a+b) (926 to 785 g/kg CP) was indicative of high protein solubility and rumen degradable protein (RDP) decreased with increasing maturity. Consequently, microbial protein synthesis and net energy of lactation (NEL) decreased linearly while rumen undegradable protein (RUP) and digestible undegradable protein (DUP) increased linearly with increasing herbage maturity. These results are interpreted to mean that G. sepium herbage quantity and quality is influenced by pruning management.

Forage yield and nitrogen nutrition dynamics of warm-season native forage genotypes under two shading levels and in full sunlight

The successful achievement of a highly productive understorey pasture in silvopastoral systems depends on the use of well-adapted forage genotypes, showing good agronomic performance and persistence under shading and grazing. In this study, the herbage dry matter yield (DMY) and nitrogen nutrition dynamics were determined in three native warm-season grasses (Paspalum regnellii, Paspalum dilatatum and Paspalum notatum) and a forage legume (Arachis pintoi) under two shading levels compared with full sun. The experiment was conducted in the Campanha region, Bagé, state of Rio Grande do Sul, Brazil, during two evaluation cycles (2008/2009 and 2009/2010). Three shade cloth levels (0%, 50% and 80% of light restriction) were applied to the forage genotypes in a split plot design, in which shading levels were the main plot and forage genotypes were the subplots, with three replications. P. regnellii showed the highest accumulated DMY (1500 and 1700 g m-2, respectively, for the first and second evaluation cycles) at all shading levels and showed no DMY decreased under the heavy shade (80%). Average DMY over the four genotypes under the 50% shade level was higher or equal compared with full sun. Influence of rainfall was observed on the DMY performance of all genotypes: the positive effect of moderate shading (50%) on P. dilatatum and P. notatum DMY was associated to a low soil water availability status. Increased shading level resulted in high nitrogen nutrition index values on grasses, in comparison with full sun. All genotypes performed well under the moderate shading level, but the DMY of both P. regnellii and P. dilatatum and the herbage N content in P. notatum and A. pintoi of all genotypes stood out, showing that those main genotypes are promising to grow in silvopastoral systems at the Campanha region in southern Brazil.

The impact of urease inhibitor on the bioavailability of nitrogen in urea and in comparison with other nitrogen sources in ryegrass (Lolium perenne L.)

Improving nitrogen (N)-use efficiency of applied urea is critical to maximise its uptake and decrease environmental impact. Two glasshouse-based studies were conducted to investigate the potential of incorporating urea fertiliser with urease inhibitor (N-(n-butyl) thiophosphoric triamide (NBPT) or ‘Agrotain’) to enhance fertiliser N uptake efficiency. Topsoil (0–0.075 m, Typic Haplustepts silt loam) from a pasture site near Lincoln, Canterbury, New Zealand, was collected and ryegrass (Lolium perenne L.) was grown from seed in standard plant trays maintained at soil moisture contents of 75–80% field capacity. Urea, Agrotain-treated urea, ammonium nitrate, ammonium sulfate, or sodium nitrate, were applied in granular form at rates equivalent to 25 or 50 kg N/ha with 4 replicates. Herbage was harvested 21 and 42 days after application of treatments to assess dry matter (DM) production, N uptake, leaf amino acid, ammonium (NH4+) and nitrate (NO3–) concentrations, and nitrate reductase activity (NRA). In a separate pot experiment, granular 15N urea (10 atom%) with or without Agrotain was applied to ryegrass at 25 kg N/ha. At 0.5, 1, 2, 3, 5, 10, and 21 days after treatment application, 3 pots per treatment were destructively sampled to determine urea hydrolysis, herbage DM, and 15N uptake. In both experiments, Agrotain-treated urea improved bio-availability of added N and resulted in significantly higher herbage DM yield and N uptake than urea alone or other forms of N fertilisers. Agrotain-treated urea applied at 25 kg N/ha increased N response by 66% compared with urea alone (and by greater proportions compared with the other fertiliser forms). Agrotain-treated urea applied at 25 kg N/ha produced significantly higher uptake efficiency (13 g DM/g of applied N) than at 50 kg N/ha (5 g DM/g of applied N). Tissue amino acids, NH4+ and NO3– contents, and NRA were not significantly influenced by any type of fertiliser. Results from the 15N experiment support the suggestion that a delay in urea hydrolysis by Agrotain provided an opportunity for direct plant uptake of an increased proportion of the applied urea-N than in the case of urea alone. Treating urea with Agrotain thus has the potential to increase N-use efficiency and herbage production.

Influence of cutting regime and fertilizer application on the botanical composition, yield and nutritive value of herbage of wet grasslands in Central Europe

AbstractThe changes in dry matter (DM) yield, botanical composition and nutritive value of herbage to ruminants of two wet grasslands, Arrhenatherum elatius grassland (Experiment 1) and a Molinia caerulea fen meadow (Experiment 2), in which a range of cutting and fertilizer treatments were imposed in 1999, were assessed after 4–7 years of treatment imposition. Both experiments had a split‐plot design with four replicates. In Experiment 1 the three main‐plot cutting treatments were two cuts with a delayed first cut, three cuts and four cuts during the growing season of each year. In Experiment 2 the cutting treatments were two cuts with a traditional harvest time, two cuts with a delayed first cut and three cuts. The four sub‐plot fertilizer treatments were an unfertilized control, application of a phosphorus and potassium (PK) fertilizer, application of a nitrogen (N) and PK fertilizer to the first cut only (N1PK) and application of PK plus N applied to each of two, three or four cuts (NcPK). Application of fertilizer influenced yield and botanical composition of herbage more than the cutting treatments while the opposite occurred for nutritive value of the herbage. Application of fertilizer increased the proportion of tall grasses in Experiment 1 and forbs in Experiment 2. The proportion of Equisetum palustre, present only in Experiment 1, was reduced from 0·33 to less than 0·01 by increased cutting frequency together with the NPK fertilizer treatments. In Experiment 1 diversity of vascular plants was negatively affected only by the four‐cuts treatment while on both wet grasslands other cutting and fertilizer application treatments had no effect. Changes in DM yield of herbage caused by the cutting and fertilizer application treatments were similar for both vegetation types with DM yield increased significantly by fertilizer application but only slightly or not reduced by increasing the cutting frequency. Nutritive value of herbage was positively correlated with cutting frequency and was most influenced at the first cut.

Effects of different rates and timing of application of nitrogen as slurry and mineral fertilizer on yield of herbage and nitrate‐leaching potential of a maize/Italian ryegrass cropping system in north‐west Portugal

AbstractEfficient use of cattle‐slurry to avoid nitrogen (N) leaching and other losses is important in designing intensive dairy systems to minimize pollution of air and water. The response in dry‐matter (DM) yield of herbage and nitrate‐leaching potential to different rates and timing of application of N as cattle slurry and/or mineral fertilizer in a double‐cropping system producing maize (Zea mays L.) silage and Italian ryegrass (Lolium multiflorum Lam.) was investigated in north‐west Portugal. Nine treatments with different rates and combinations of cattle slurry, and with or without mineral‐N fertilizer, applied at sowing and as a top‐dressing to both crops, were tested and measurements were made of DM yield of herbage, N concentration of herbage, uptake of N by herbage and amounts of residual soil nitrate‐N to a depth of 1 m, in a 3‐year experiment. Regression analysis showed that the application of 150 and 100 kg of available N ha−1 to maize and Italian ryegrass, respectively, resulted in 0·95 of maximum DM yields of herbage and 0·90 of maximum N uptake by herbage. Residual amounts of nitrate‐N in soil after maize ranged from 48 to 278 kg N ha−1 with an exponential increase in response to the amount of N applied; there were higher values of nitrate‐leaching potential when mineral‐N fertilizer was applied. The results suggest that it is possible in highly productive maize/Italian ryegrass systems to obtain high DM yields of herbage for maize silage and Italian ryegrass herbage with minimal leaching losses by using slurry exclusively at annual rates of up to 250 kg available N ha−1 (equivalent to 480 kg total N ha−1) in three applications.

Yield and nutritive value of timothy as affected by temperature, photoperiod and time of harvest

AbstractScenarios of global climate change forecast an increase in air temperature of 3°C over the next 100 years in eastern Canada. Growth and nutritive value of cool‐season grasses are known to be affected by air temperature. It is also believed that grasses grown at high latitude have a greater nutritive value. The objectives of this study were to assess the effect of four combinations of day/night temperature and photoperiod (15 h–17/5°C; 15 h–22/10°C; 15 h–28/15°C; and 17 h‐17/5°C) on dry‐matter (DM) yield, in vitro true DM digestibility (IVTD), in vitro digestibility of neutral‐detergent fibre (NDF), and concentrations of NDF, acid‐detergent fibre (ADF), lignin, minerals and non‐structural carbohydrates (NSC) in timothy grown under controlled conditions. Furthermore, herbage was harvested in the morning and in the afternoon to assess the impact of the time of harvest. The dietary cation–anion difference [DCAD = (K+ + Na+) − (Cl− + 0·6 S2−)] and the grass tetany index [GT index = K+/(Ca2+ + Mg2+)] were also calculated. Higher temperature regimes significantly decreased IVTD and digestibility of NDF but had a limited effect on concentrations of NDF, ADF and lignin. DM yield of herbage was less and the concentration of NSC was greater in timothy grown under a temperature regime of 28/15°C than the 17/5°C and 22/10°C regimes; this effect is mainly explained by a response to temperature stress. Values of DCAD and the GT index of herbage were also lower under the 28/15°C than the 17/5°C and 22/10°C regimes as a result of a decreased plant K concentration. Under the 17/5°C regime, an increase in 2 h of photoperiod resulted in increased DM yield, decreased concentrations of K, Ca, Mg, Cl and N, and an increased starch concentration; IVTD or digestibility of NDF were not affected, although lignin concentration was reduced. Harvesting timothy in the afternoon rather than in the morning resulted in higher NSC, mainly sucrose, concentrations, and decreased ADF and NDF concentrations. The forecasted increase in air temperature in eastern Canada over the next 100 years will result in lower yields and nutritive value of timothy.

Effects of tractor wheeling on root morphology and yield of lucerne (Medicago sativa L.)

SummaryThe purpose of this study was to determine the effect of soil compaction on the herbage yield and root growth of lucerne (Medicago sativa L.). A field experiment was conducted on a silty loam Mollic Fluvisols soil in 2003–2006. Herbage yield and root morphology, in terms of root length density, mean root diameter, specific root length and distribution of dry matter (DM) in roots, were measured. Four compaction treatments were applied three times annually by tractor using the following number of passes: control without experimental traffic, two passes, four passes and six passes. The tractor traffic changed the physical properties of the soil by increasing bulk density and penetration resistance. Soil compaction also improved its water retention properties. These changes were associated with changes in root morphology and distribution of the DM in roots. Soil compaction resulted in higher proportions of the DM in roots, especially in the upper, 0–10 cm, soil horizon. Decreases in the root length density were observed in a root diameter range of 0·1–1·0 mm. It was also found that roots in a more compacted soil were significantly thicker. An effect of the root system of lucerne on soil compaction was observed. The root system of lucerne decreased the effects of soil compaction that had been recorded in the first and the second year of the experiment. An increase in the number of passes resulted in a decrease in the DM yield of herbage in the second and third harvests each year.

Benefits of winter legume cover crops require early sowing

Winter cover crops are beneficial, especially legumes that can supply nitrogen (N) to the next crop. The purpose of this study, involving separate experiments carried out at 2 different locations in north-eastern Slovenia, was to determine the most appropriate sowing time (early, early autumn SD1; late, mid autumn SD2; very late, late autumn SD3) for winter legumes (Trifolium subterraneum L., T. incarnatum L., T. pratense L., and Vicia villosa Roth) for the optimal yield of beneficial dry matter and soil N cycling. The control treatment used Lolium multiflorum Lam. For legume cover crops in SD1, from 915.0 (T. subterraneum) to 2495.0 (V. villosa) kg herbage dry matter yield (HDMY)/ha, 52.3 (T. pratense) to 148.4 (T. incarnatum) kg accumulated N (AN)/ha, and 14.5 (T. pratense) to 114.5 (T. incarnatum) kg symbiotically fixed N (Nsymb)/ha was obtained to the end of autumn. Until the spring ploughing-in, which was before maize sowing, legume cover crops in SD1 yielded 1065.0 (T. subterraneum) to 4440.0 (T. incarnatum) kg HDMY/ha, 74.9 (T. subterraneum) to 193.0 (V. villosa) kg AN/ha, and 4.7 (T. subterraneum) to 179.0 (V. villosa) kg Nsymb/ha. All parameters in SD2 were significantly lower than in SD1, whereas the SD3 sowing was not suitable for the legumes. The benefits of legume winter cover crops with regard to symbiotic N fixation were achieved only by early sowing; however, the amount of soil mineral N in late autumn and in early spring was decreased under L. multiflorum more than under the legumes.

Quantifying the damage of red deer (Cervus elaphus) grazing on grassland production in southeastern Slovenia

The influence of red deer (Cervus elaphus) grazing on grassland production for forage conservation at the forest border during the vegetation period was studied on three locations (Mala gora, Cvislerji, and Mackovec) in the Kocevje region (SE Slovenia). The experiment lasted from the 25th of March until the 8th of October 2002. Portable cages were used to exclude red deer from grazing the herbage. At four sampling dates in the season, herbage air dry matter (DM) yield was measured at three different observations (cage-protected plot, cage-protected plot only two to three weeks before sampling date, otherwise freely grazed (removed), and unprotected plot). The results from the experiment showed that red deer grazed on grassland through the entire season and that the regeneration capability of sward was the highest in summer, middle in spring and smallest in autumn. On unprotected plots, an average reduction of 50% of herbage DM yield was found with the most damaged sites also up to 80% reduction.

Variation of productivity and nutritive values of oat (Avena sativa) with geographical locations in Gansu Province of Northwest China under irrigation and fertilization conditions

Field experiments were conducted in low, medium and high sites; Jingqianghe, Huangzangsi and Lanzhou areas of Gansu Province, China from 2000 to 2001 to investigate the effects of geographical locations on herbage dry matter (DM) yield and nutritive values of oat. It was found that the plant growing in Jingqianghe area yielded the highest forages (16046.0 DM/hm2) at high accumulation rate (300 kg ha-1d-1) and within long growing season (120 d), the plant growing in Huazangsi area produced medium quantity of forages (13020.3 DM/hm2) at low accumulation rate (200 kg ha-1d-1) but within long growing season (120 d), and the plant growing in Lanzhou area had the lowest forage yield (12505.7 kg DM/hm2) at relatively high accumulation rate (270 kg ha-1d-1) but within extremely short growing season (50 d). The highest seed production of 3789.3 kg DM/hm2 annually was observed in Huangzangsi area, the lowest seed production of 933.7 kg DM/hm2 annually was found in Jingqianghe area, and the medium seed production of 1632.7 kg DM/hm2 annually was recorded in Lanzhou area. The plant growing in high site of Jinqianghe area concentrated more (P growing in low site of Lanzhou area, and no significant difference in organic matter (OM), crude protein (CP) and crude fibre (CF) concentrations of the plant was observed among different growing sites. No significant difference (P > 0.05) in in sacco degradability (ISD) of the plant among different growing sites was observed in the whole growing season. It was concluded from this study forage production should be conducted in high site of Jingqianghe area and seed production of oat should be conducted in low site of Lanzhou area with enough water and fertilizer supply.

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

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