An examination of the effect of autumn closing date on over-winter herbage production and spring yield

Altering autumn management affects the herbage mass available in spring. An experiment was established to determine the effect of five autumn closing dates (CDs) on herbage production, herbage quality, leaf, stem and dead proportions and tiller density over winter. In the study 50% of the herbage available in spring was accounted for by autumn CD. Each 1 d extra a sward was closed from 25 September to 9 December increased herbage mass by 16 kg DM/ha in spring. Swards closed earlier (25 September–26 October) had consistently higher herbage masses in spring (1,301 kg DM/ha) compared to swards closed later (11 November–9 December; 703 kg DM/ha). Later closed swards had greater herbage quality compared to earlier closed swards (organic matter digestibility = 852 and 825 g/kg DM, respectively) due to increased stem and dead material in the grazing horizon of earlier closed swards. There was no effect of autumn CD on sward quality in the subsequent defoliation in spring. However, following the initial spring grazing there was an effect of autumn CD on subsequent grass growth rates; swards closed in October had a lower growth rate (33 kg DM/ha per day) compared to swards closed in November and early December (49 kg DM/ha per day). Results indicate that earlier autumn closing is beneficial to meet high-feed demand in spring but can affect sward quality and growth rates in spring.

Can Grazing Moderate Climatic Effects on Herbage Nutritional Quality?

In Mediterranean grasslands, the composition of vegetation and its nutritional quality for animals are strongly affected by the climatic conditions prevailing during winter and spring. Therefore, these seasonal ecosystems provide an opportunity to examine how variability in climatic conditions affects the regeneration and quality of pasture vegetation. The intensity of grazing in this seasonal system can moderate, or alternatively exacerbate, climatic effects on the nutritional quality of the vegetation. Herein, we analyzed the interactive effects of climate variables, grazing intensity, and grazing exclusion on herbage quality parameters using long-term vegetation and climate data collected during 2005–2018 from an extensive experiment in Galilee, Israel. We evaluated the contribution of different climate variables to the prediction of herbage quality parameters. Our results showed that climate variables have a dramatic effect on herbage quality and that this effect interacts with grazing intensity. Herbage quality improved in temperate rainy years compared to warm and dry years. High grazing intensity improved herbage quality under temperate climate conditions, but this effect was moderated or completely disappeared as winter conditions become warmer and drier. The results of the study foresee negative effects of warming and drying on the carrying capacity of natural pastures.

Selection for resistance to fungal diseases and other desirable traits in kikuyu grass (Cenchrus clandestinus)

While kikuyu (Cenchrus clandestinus) is an important grass for dairy and beef production in the subtropical region of Australia and the world, the most common cultivar, Whittet, is seriously affected by the fungal diseases, kikuyu yellows (Verrucalvus flavofaciens) and black spot (Bipolaris spp.). Thus resistance to these diseases is a priority in selecting a better kikuyu cultivar, along with higher herbage quality and yield and better winter growth. A study was conducted to identify suitable candidates from kikuyu ecotypes collected along the east coast of Australia plus lines obtained by subjecting Whittet to a mutagenic agent. Initial glasshouse studies identified 19 lines that were resistant to the KY1A strain of kikuyu yellows and 4 of these, with forage quality and yield superior to Whittet, were further evaluated in the field at 2 sites using Whittet as the control. At Site 1, line 12A demonstrated a much higher level of resistance to kikuyu yellows than Whittet, with 85% of plants resisting infection compared with only 15% of Whittet plants. At Site 2, the numbers of 12A and Whittet plants infected were similar. Further tests, using kikuyu yellows inoculum collected from 11 sites along the east coast of Australia, found that only 15% of 12A plants became infected compared with 61% of Whittet plants. Thus, kikuyu line 12A was resistant to most, but not all, strains of the kikuyu yellows pathogen. Annual yield of 12A (19,008 kg DM/ha) was 24% higher than that of Whittet and 12% higher than Acacia, but the difference was significant only for Whittet. During summer, 12A produced 10,212 kg DM/ha (24% higher than Whittet), was more active in early spring, had slightly higher dry organic matter digestibility (66.7 vs. 64.0%) and was resistant to black spot infection.

Interactions between biogeochemical and management factors explain soil organic carbon in Pyrenean grasslands

Grasslands are one of the major sinks of terrestrial soil organic carbon (SOC). Understanding how environmental and management factors drive SOC is challenging because they are scale-dependent, with large-scale drivers affecting SOC both directly and through drivers working at small scales. Here we addressed how regional, landscape and grazing management, soil properties and nutrients, and herbage quality factors affect 20 cm depth SOC stocks in mountain grasslands in the Pyrenees. Taking advantage of the high variety of environmental heterogeneity in the Pyrenees, we built a dataset (n=128) that comprises a wide range of environmental and management conditions. This was used to understand the relationship between SOC stocks and their drivers considering multiple environments. We found that temperature seasonality (difference between mean summer temperature and mean annual temperature; TSIS) was the most important geophysical driver of SOC in our study, depending on topography and management. TSIS effects on SOC increased in exposed hillsides, slopy areas, and relatively intensively grazed grasslands. Increased TSIS probably favours plant biomass production, particularly at high altitudes, but landscape and grazing management factors regulate the accumulation of this biomass into SOC. Concerning biochemical SOC drivers, we found unexpected interactive effects between grazer type, soil nutrients and herbage quality. Soil N was a crucial SOC driver as expected but modulated by livestock species and neutral detergent fibre contenting plant biomass; herbage recalcitrance effects varied depending on grazer species. These results highlight the gaps in knowledge about SOC drivers in grasslands under different environmental and management conditions. They may also serve to generate testable hypotheses in later/future studies directed to climate change mitigation policies.

The effect of stage of regrowth on the physical composition and nutritive value of the various vertical strata of kikuyu (Cenchrus clandestinus) pastures

A plot study was conducted at the Gatton Research Dairy, Queensland, Australia, to quantify the effects of 5 regrowth periods (9, 11, 14, 16 and 18 days) and 4 vertical strata on the composition and nutritive value of kikuyu (Cenchrus clandestinus) pastures using a block factorial design with 4 replicates. Pasture samples were analyzed for crude protein (CP), ethanol-soluble carbohydrates (ESC), acid detergent fiber (ADF), neutral detergent fiber (aNDFom), in vitro indigestible neutral detergent fibre (iNDF240) and minerals. Metabolizable energy (ME) was then calculated from the concentrations of other nutrients. Regardless of the stage of regrowth, stems were located mainly in the bottom 1 or 2 strata, while leaves were present mainly in the top 2 or 3 strata. CP, ESC and ME declined, but aNDFom, ADF and iNDF240 increased with stage of regrowth and from top to bottom of the swards (P<0.05). While herbage quality variables were affected by both factors, vertical stratum had a much larger impact on quality than stage of regrowth. These results indicate that grazing management of kikuyu pastures should be based not only on stage of regrowth but also on level of defoliation, as both have strong impacts on the nutritive value of the consumed forage.

Interacting abiotic, biochemical and management factors explain soil organic carbon in Pyrenean grasslands

&lt;p&gt;Grasslands are one of the major sinks of terrestrial soil organic carbon (SOC). Understanding how environmental and management factors drive SOC is challenging because there are scale-dependent effects, and large scale drivers affecting SOC both directly and through drivers working at fine spatial scales. Here we address how regional and landscape factors, and grazing management, soil properties and nutrients, and herbage quality factors affect SOC in mountain grasslands in the Pyrenees. Taking advantage of the high variety of environmental heterogeneity in the Pyrenees, we fitted a set of models with explicative purposes including variables that comprise a wide range of environmental and management conditions. We found that temperature seasonality (MMT) was the most important abiotic driver of SOC in our study. MMT was positively related to SOC but only under certain conditions: exposed hillsides, steep slopes and relatively highly grazed areas. High MMT conditions probably are more favourable for plant biomass production, but landscape and grazing management factors buffer the conversion of this biomass into SOC. Concerning biochemical SOC predictors, we obtained some unexpected interaction effects between grazer type, soil nutrients and herbage quality. Soil N was a crucial factor modulated by effects of livestock species and neutral-detergent fibre content of vegetation. Herbage recalcitrance effects varied depending on grazer species. These results highlight the need to expand knowledge about grassland SOC drivers under different environmental and management conditions.&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;

Interactions between biogeochemical and management factors explain soil organic carbon in Pyrenean grasslands

Grasslands are one of the major sinks of terrestrial soil organic carbon (SOC). Understanding how environmental and management factors drive SOC is challenging because they are scale-dependent, with large scale drivers affecting SOC both directly and through drivers working at detailed spatial scales. Here we addressed how regional, landscape and grazing management, soil properties and nutrients and herbage quality factors affect SOC in mountain grasslands in the Pyrenees. Taking advantage of the high variety of environmental heterogeneity in the Pyrenees, we fit a set of models with explicative purposes using data that comprise a wide range of environmental and management conditions. We found that temperature seasonality (MMT) was the most important geophysical driver of SOC in our study. MMT was positively related to SOC but only under certain local conditions: exposed hillsides, steep slopes and relatively highly grazed areas. High MMT conditions probably are more favourable for plant biomass production, but landscape and grazing management factors buffer the accumulation of this biomass into SOC. Concerning biochemical SOC predictors, we obtained some surprising, interactive effects between grazer type, soil nutrients and herbage quality. Soil N was a crucial factor modulating effects of livestock species and neutral detergent fibre content of plant biomass and herbage recalcitrance effects varied depending on grazer species. These results highlight the gaps in the knowledge about SOC drivers in grassland under different environmental and management conditions, and they may serve to generate testable hypothesis in latter studies directed to climate change mitigation policies.

An on-farm study of the herbage quality and sward characteristics of plantain-clover mixes during late summer and autumn and resulting lamb growth rates

An on-farm study investigated the herbage quality and sward characteristics of plantain-clover mixes and resulting lamb growth rates during late summer and autumn. Three farms were chosen, each with a minimum of 10 ha of plantain-clover mix (Plantago lanceolata ‘Ceres Tonic’, Trifolium pratense, Trifolium repens) used for lamb finishing. Each farm managed the plantain-clover mix area using their routine management without advice or comment from research staff. Throughout autumn, at approximately monthly intervals on the three farms, the pre- and post-grazing herbage masses, botanical composition, herbage quality, plantain dry matter content, secondary chemical composition and lamb growth rates were monitored. A low percentage of clover in the sward, a high percentage of dead stem material and a low crude protein concentration in plantain during dry periods, were identified as the most likely causes of low lamb liveweight gains during autumn. Grazing management during spring that maintains control of plantain stems and encourages the presence of clover, appears to be a key management technique for ensuring high lamb liveweight gains on plantain-clover mixes in late summer and autumn.

Production and quality benefits of white clover inclusion into ryegrass swards at different nitrogen fertilizer rates

A 4-year (2010–2013) plot study was undertaken to evaluate the effect of nitrogen (N) fertilizer rate (0, 60, 120, 196 and 240 kg N/ha/year) on seasonal responses and species persistency in frequently and tightly grazed (⩽4 cm) grass-only (GO) and grass white clover swards (GWc). Increasing N application rate increased herbage removed and pre-grazing sward height. Cows frequently grazed the GWc tighter than the GO. Increasing N rate reduced clover content, especially during the warmest months of the year, but less so up to 120 kg N/ha/year. The GWc had greater amounts of herbage removed than GO in the May–September period but the effect was less as N rate increased. Cumulative herbage removed from GWc was greater than GO swards receiving the same N rate and herbage quality was better in GWc than GO. Such effects were reduced as swards aged and with increasing N rate. It was concluded that under frequent and tight grazing management: (1) clover inclusion increased annual herbage removed; (2) herbage removed from GWc swards receiving no N was the same as the GO sward receiving 240 kg N/ha, and greater for the 240 GWc swards than the 240 GO swards; (3) clover inclusion benefits were mainly from summer onwards; (4) the management strategy applied in the current experiment may be capable of alleviating the detrimental effect of N fertilizer on clover, to a point between 60 and 120 kg N/ha.