The effects of lime on pasture composition and production in western Waikato hill country

A 4-year lime rate trial was established on a hill country sheep and cattle property near Te Akau to determine lime effects on pasture utilisation. Four rates of lime were applied (1.25 t/ha, 2.5 t/ha, 5 t/ha and 10 t/ha) to 2 m × 2 m plots, from which soil Al, Ca and pH, pasture grazing heights, dry matter production, pasture species composition, feed quality and brix levels were measured. Lime application reduced soil Al (14.6 to 1.1 mg/kg), and increased Ca and pH (5.0 to 6.2) over time in the highest application rate. Dry matter production responded to all rates of lime in each year, and by the fourth year it was 27% greater (1.25 t/ha treatment), 35% greater (2.5 t/ha treatment), 69% greater (5 t/ha treatment), and 97% greater (10 t/ha treatment) than in the un-limed plots. Ryegrass and subterranean clover content increased with lime rate, whereas chewings fescue and dicot weed content declined. There were no sustained differences in pasture grazing heights, feed quality or brix levels between the control and rates of lime. On this site, all rates of lime were economic to apply by truck or plane when the benefits were spread over 4 years, with the greatest cost-benefit from thelower rates of lime.

Improving grassland/forage quality and management to reduce livestock greenhouse gas emissions

This chapter reviews grazing management strategies that can contribute to reducing livestock greenhouse gas emissions. Strategies discussed include grazing season length and timing as well as sward structure and quality, including dry matter and clover content. The chapter also discusses the use of condensed tannin legumes such as chicory and plantain, as well as measurement issues including life cycle assessment.

White clover incorporation at high nitrogen application levels: results from a 3-year study

Context High nitrogen (N)-fertiliser application levels and high stocking rates have been shown to optimise herbage dry-matter (DM) production in grass-only systems. Conversely, swards including white clover (Trifolium repens L.) are commonly suited to production systems at low N-fertiliser application levels (<150 kg N/ha) and low stocking rates (fewer than two livestock units (LU) per hectare). Despite this, the use of N fertiliser on grass–clover swards has generally increased during the past few decades, particularly in more intensively managed swards under dairy farming. Increasing inorganic N decreases sward white clover content in grass–clover swards, and increasing stocking rate on grass–clover swards can result in damage to white clover plants. However, under high N-application levels, a high stocking rate can also potentially minimise the negative effects of increased grass growth on sward white clover content. Aims The objective of the present study was to investigate the persistency of white clover in an intensive animal-grazing system, under a high N-fertiliser application level (250 kg N/ha) and at a high stocking rate (2.75 LU per hectare) over a 3-year period (2014–2016). Methods The study was a 2 × 2 factorial design, consisting of two perennial ryegrass ploidies (diploid, tetraploid) and two white clover treatments (grass-only, grass–clover). Four sward treatments (diploid-only, tetraploid-only, diploid + clover, tetraploid + clover) were evaluated over a full grazing season at a system scale. Sward measurements were taken at each grazing occasion for 3 years. Key results Over the 3 years, grass–clover swards produced an additional 1468 kg DM/ha when compared with grass-only swards. Sward white clover content decreased by 17% over the three study years. Conclusions This decrease in sward white clover content led to a decrease in contribution to cumulative herbage DM production. Implications Although the present study showed that white clover inclusion can increase herbage DM production at high N-fertiliser application levels, in association with high stocking rates, the initial extra herbage DM production on grass–clover swards decreased each year. Further studies should be undertaken to investigate whether the decline in white clover persistence observed is progressive over a longer time period.

Maximising the subterranean clover content on a summer-dry Wairarapa hill-country farm through grazing management

Tokaroa Farm is a 608-ha sheep and beef farm, in the Wairarapa. Paddock slopes range from flat to steep (>25°) with a predominance of gentler north facing slopes and steeper south facing slopes. Annual rainfall is 810 mm and average summer dry is three months. Resident subterranean (sub) clover (Trifolium subterraneum L.) populations were identified on an uncultivatable north-west facing hill slope in 2015, and a management plan devised to increase its contribution to pastures. Exclosure plots showed that an eight-week spell in spring 2016 increased resident sub clover groundcover from 13 to 54%, while in the lightly grazed paddock control sub clover increased from 10 to 28%. There was a positive linear relationship (R2=0.51) between the total number of established sub clover seedlings on 30 March 2017 and the previous spring sub clover groundcover (%) on 25 November 2016. In October 2017, the effect of the spring 2016 exclosure treatments was still evident with 57% sub clover groundcover in the eight-week spelled areas compared with 37% in the control despite all the exclosures being grazed in 2017.Sub clover management strategies were developed, using slope and aspect, and applied to a GIS map of Tokaroa Farm. This suggested that 53% of the farm could have sub clover overdrilled into it and 29% could have the resident sub clover population actively managed and/or oversown with sub clover seed.

Comparative effect of alternative fertilisers on pasture production, soil properties and soil microbial community structure

Different fertiliser products are commonly promoted for use on pastures in order to improve pasture productivity and support a more ‘healthy’ soil microbial environment. However, minimal field research has been conducted to validate such claims. A 6-year study (2009–14) was conducted on phosphorus (P)-deficient soils at three sites near Yass, New South Wales, to investigate the effect of topdressing perennial native-based pastures with a range of alternative fertilisers compared with single superphosphate and an unfertilised control treatment. The alternative fertiliser products included manures, composts, crushed rock, rock-phosphate-derived products, concentrated ash and microbial products. Annual measurements were made of soil chemical properties, botanical composition and pasture yield during spring and/or winter + spring, as well as the relative effectiveness of products per unit of pasture grown. Soil microbial community structure under each fertiliser treatment was also analysed in the sixth year of the study. Fertiliser products with substantial quantities of P increased extractable soil P and resulted in significantly higher pasture growth and clover content compared with the unfertilised control. Superphosphate was found to be the most P-effective fertiliser for increasing pasture growth, along with a range of other products that showed differential responses. However, the cost and P-effectiveness of the products in relation to pasture growth varied considerably and was a function of rate and frequency of application as well as amount and solubility of the P applied. Despite large differences in pasture growth across the various fertiliser treatments, there was no significant effect of the alternative fertiliser products on microbial community structure compared with either the superphosphate or unfertilised control treatments. The observed variation in bacterial, fungal and archaeal community structures across all fertiliser treatments was best explained by soil pH or aluminium (Al) concentration, which was influenced differentially by the fertiliser products. Fungal community structure was also correlated with pasture-productivity parameters (i.e. spring pasture yield, clover content and soil-available P). Our findings reveal a highly resilient soil microbial community that was influenced minimally by use of the alternative fertiliser products, thus highlighting that on-farm management decisions regarding fertiliser product choice should primarily focus on pasture response and cost-effectiveness.

Metabolisable energy concentration in perennial ryegrass pastures: multi-site analysis of effects of cultivar, nitrogen fertiliser and white clover content

To include metabolisable energy (ME) as a nutritive value factor for ryegrasses in the Forage Value Index (FVI) requires data for New Zealand cultivars on the effects of environmental and management factors on cultivar ranking. This study tested the hypothesis that variation among cultivars, and so ranking, is not influenced by environment, nitrogen (N) fertiliser level or the presence or absence of white clover. Eight cultivars, grown with or without white clover and at two levels of N fertiliser in grazed pastures in Waikato, Manawatū, Canterbury and Southland, were sampled seasonally over 3 years and analysed for ME. There were clover, N and cultivar main effects on ME in most seasons, however, there were no interactions that affected cultivar ranking, indicating that data from field evaluation systems based on monocultures are reliable for the purposes of the FVI. However, data for absolute ME concentration are required from multiple sites to account for the observed cultivar × environment interactions.

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.

Profitability of controlled traffic in grass silage production – economic modelling and machinery systems

Controlled traffic farming (CTF) systems aim to reduce soil compaction by restricting machinery field traffic to permanent traffic lanes. Grass-clover silage production is generally associated with intensive field traffic, resulting in reduced silage clover content. If CTF can increase yield and clover content in grass-clover leys, this would reduce the need for grain and expensive protein concentrate in dairy cow feed rations. A mixed integer programming model was developed to evaluate the potential profitability of CTF in a dairy farm context. Existing field trial data were used to calculate the expected yield outcome of CTF, based on reductions in trafficked area. The results revealed that CTF increased profitability by up to €50/ha. Total machinery costs are likely to increase on converting to CTF, but variable machinery costs are likely to decrease.

Tolerance of newly sown cocksfoot-clover pastures to the herbicide imazethapyr

In New Zealand, subterranean clover is recommended as a companion legume in mixed swards, particularly in dryland cocksfoot-based pastures. However, establishment of cocksfoot is slower than perennial ryegrass and therefore weed ingress is more common. An experiment at Lincoln University, Canterbury showed imazethapyr applied when clover was at the 3-4 trifoliate leaf stage, and cocksfoot at the 2+ leaf stage, increased the subterranean clover content of the pastures by at least 1000 kg DM/ha, despite initial visual phytotoxicity responses. Balansa and white clover pasture yields were not different to their unsprayed unweeded controls. Imazethapyr application controlled broadleaf weeds from early in the season. The herbicide application reduced cocksfoot yields by 70% in early spring, but yields recovered and were not different to the unsprayed unweeded controls at 1350 ± 260 kg DM/ha after grazing. Imazethapyr application improved subterranean clover pastures through an increase in clover content by suppressing weeds and temporarily reducing the rate of cocksfoot growth. Keywords: subterranean clover, Spinnaker herbicide, seedling, white clover, balansa clover

Improving summer and autumn feed quality in New Zealand hill country

Management of late spring surpluses to restrict reproductive growth can increase the quality of hillcountry pastures during summer and autumn. This occurs through a reduction in accumulated stem and dead material and an increase in clover content. However, there is little information on the magnitude and longevity of these effects. This trial investigated the effects of four late spring defoliation intensities on herbage quality, measured at the end of spring and during summer. Treatments were applied through regular cutting of hill pastures in areas of medium fertility and slope on two aspects in each of four geo-climatically different hill-farming regions over two years. Pasture herbage quality at the end of spring followed expected trends: defoliation to low residual pasture height led to higher quality herbage. The maximum difference in quality between the lowest cutting height and nil cutting at this time was nearly 2 MJME/kg DM. With a change to uniform cutting height across all plots in early summer, these pasture quality differences reduced and disappeared. Keywords: Pasture quality, hill country, grazing management