New-generative agriculture – based on science, informed by research and honed by New Zealand farmers

Highlights Regenerative agriculture is being promoted as a way to produce food sustainably while building soil carbon under high residual rotational grazing and minimising environmental impact. Research indicates that the environmental impact of conventional agricultural systems is generally lower than for alternative systems per unit of food production and sometimes per hectare. Soil carbon is higher under well-managed intensive grazing than under extensively managed systems. Adopting non-optimal grazing management decreases pasture quality and increases GHG and N losses. New Zealand has developed optimal rotational grazing and has soils with high organic-matter contents. Rather than adopting a concept developed overseas which has a fluid definition, New Zealand could promote New-generative agriculture… encapsulating what is already being done.

Impact of change in body condition score in mid-late pregnancy in ewes fed a mixed diet on lamb survival and performance

The objective of this study was to evaluate the effect that body condition score of pregnant ewes fed on turnip and swede crops during mid-late gestation had on offspring survival and performance. Data were collected from 755 multiparous mixed-age ewes carrying 1–4 fetuses. Ewes grazed a turnip crop for 1 month prior to pregnancy scanning with supplementary ryegrass/clover baleage (~75 days gestation) followed by a swede crop with supplementary Lucerne baleage for 1 month following pregnancy scanning (to ~120 days gestation). Ewe body condition score (BCS) at mating, pregnancy scanning and pre-lambing, along with lamb survival and growth rates to weaning were recorded. Lamb survival from pregnancy scanning to tailing differed by litter size (P<0.001) with lower survival in litters with 3 or more lambs compared to singles and twins which did not differ. Improving BCS from pregnancy scanning to 120 days gestation had a positive effect on lamb survival irrespective of litter size and ewe age (P<0.001). Lamb survival in ewes ≥5 years of age, irrespective of litter size, was lower (P<0.001) compared to 2 or 3–4-year-old ewes, which in turn did not differ from each other. The key finding of the study was that loss in BCS from pregnancy scanning to 120 days gestation, negatively impacted on lamb survival, especially in ewes carrying 3 or more fetuses and in ewes >5 years of age irrespective of the number of fetuses carried. Furthermore, there was high variation in BCS change observed in both early and mid-pregnancy.

Quantifying the value proposition for white clover persistence on a New Zealand summer-dry hill-country farm

The improvement in forage quality and quantity of summer-dry hill country pasture resulting from the introduction of clover is well recognised. However, ensuring the persistence of the commonly availablecultivars is challenging, in the face of seasonal moisture stress, intensive grazing, competition from established well-adapted pasture species, low soil fertility and low soil pH – conditions typical of the East Coast of the North Island. Here we quantify the value proposition associated with the introduction of white clover into a case study on a Gisborne sheep and beef farm, using a six-step process. A topographically explicit approach is taken, using an understanding of the underlying spatial variability, based on a combination of soil and pasture measurements, APSIM simulation modelling of pasture growth and farm system modelling of enterprise performance. We show that from a baseline of a typical low-fertility, diverse species hill country pasture, white clover introduction can increase spring and summer forage consumption by 17%, enabling inclusion of an additional 6-month bull finishing enterprise generating a 32% greater carcass weight production and leading to a 49% improvement in farm system EBIT. This represents a positive net present value of over $360,000 for the original investment in white clover establishment into existing pastures.

Commercial practice of out-wintering dairy heifers in Great Britain

The majority of dairy cattle in Great Britain (GB) are housed during winter but replacement heifers are out-wintered on some farms, a practice that may reduce the need for high capital-cost housing and facilitate herd expansion. Dairy farmers that were out-wintering replacement heifers in GB in 2012 were surveyed to determine current practice and attitudes. A typical system involved heifers strip grazing pasture or a crop, with baled grass silage as supplementary feed; strongly resembling outdoor wintering systems in New Zealand. Many used more than one grazed forage; predominantly, pasture on 68%, kale on 53% and fodder beet on 33% of farms. Supplementary feed was 44% of the diet in younger, and 35% in older heifers. Although farms were approximately three times larger than the national average and 60% were expanding, expanding herd size was not the primary reason for out-wintering, with the main reasons being to reduce cost and improve animal health and welfare. Farmers that out-wintered heifers typically reported good animal average dairy gain of 0.6 kg/d and high body condition, however, this contrasts with some measured performance in GB. Farmers may benefit from accurate feed allocation and monitoring heifer live weight during winter to ensure high performance.

Mitigation of saturation in satellite pasture measurement via incorporation of a statistical pasture growth model

Measurement of pasture biomass is useful to farmers, as it enables timely and accurate management decisions. Satellite pasture measurement allows this information to be obtained with minimal time and labour on the part of the farmer. However, the accuracy of satellite measurements for high levels of pasture biomass can be impacted by a phenomenon called saturation, in which the response of the satellite estimate to increased biomass is diminished in situations of high biomass. In this investigation, a statistical pasture growth model was combined with satellite pasture measurements, with the aim of mitigating the effect of saturation on estimation accuracy. Data were captured for five farms, across two regions and an 18–21 month measurement period. Where satellite measurements appeared to be saturated, the growth model estimate was substituted. This process resulted in improved accuracy (R2 improved from 0.672 to 0.703; RMSE improved from 334 to 309 kg DM/ha; and average bias improved from -62 to -9 kg DM/ha). The statistical improvements were more pronounced where terrestrial estimates were higher so the impact of saturation would be greatest. These results indicate that the problem of saturation in satellite pasture measurement can be addressed by the incorporation of modelled data. Prior research has predicted that improved accuracy of pasture measurement would be associated with increased profitability, and this work helps achieve that goal for farmers using satellite measurement services.

Can Lotus pedunculatus over-sowing in low-fertility tussock country increase farm resilience?

The range of legumes to boost farm productivity in low-fertility hill country are limited. Lotus pedunculatus (Lotus) provides an option when soil pH is below 5 but is intolerant to severe and regular grazing. However, itcan be used at sites that are only grazed occasionally during spring summer and autumn. Oversowing of Lotus pedunculatus has been used to improve 17% of the total area of Avenel Station, Millers Flat. Measurements of pasture growth and animal production were collected over three years post-sowing, indicating a doubling of pasture production from the native form while providing liveweight gains of 0.135 and 0.75 kg/d in lambs and yearling cattle respectively. Systems modelling was used to re-examine the current farm-system configuration to test the possible outcomes from implementing further enterprises that may capture the increased late spring and summer production effectively. Reducing ewe numbers and concentrating on improving lamb survival were the most cost-effective and environmentally effective options. Buying in further finishing lambs to use the summer surplus also improved profitability. Increasing cow numbers was similarly profitable. Increasing ewe numbers also required an increase in winter feed supply and was the least profitable way to capture the benefits. Testing using climatic extreme scenarios demonstrated that the oversowing of Lotus on the higher, wetter tussock country increased the resilience of the farm by providing a buffer during dry summers.

Potential profit gains from improving pasture productivity on New Zealand South Island high-country farms

Soil acidity combined with low levels of key nutrients on New Zealand hill-country farms are limiting factors for legume establishment/growth. However, legumes are a critical component of these farms as they provide nitrogen and high-quality feed. A farm-systems model was developed to estimate the impact of targeted fertiliser and lime application, combined with sowing clover, on whole-farm productivity and profitability. A base model was developed that incorporated 17 years’ worth of Beef + Lamb NZ survey data for Class 1: South Island Farms. This base model was then used investigate two lime-application/oversowing models where part of the modelled high-country farm was targeted for improvement: (1) Conservative, i.e. 0.6% farm area; and (2) Aggressive, i.e. 2.8% farm area. Three scenarios to utilise the additional pasture grown were then investigated for each model by: (a) increasing ewe numbers; (b) increasing ewe performance (lambing percentage); and (c) increasing liveweight gain of stock. Scenario 2a, generated the highest profitability level (Earnings before Interest Tax and Rent, EBITR $58,870) above the base model but became less financially attractive when the two years required to build the maternal ewe flock were factored in. Scenarios 2c and 1b generated increases in profitability (EBITR) between $33,310 and $41,290 above the base model. Variation in product prices, production levels and time to develop the final farm-management system would also influence the productivity and profitability of the scenarios. Environmental aspects, infrastructure and staff availability would affect the suitability of the development for individual farming businesses.

Persistence of perennial ryegrass, tall fescue and cocksfoot following sequential annual sowings: pasture yield, composition and density in three establishment years under cattle grazing in Waikato

Persistence is an important component of perennial pasture-grass productivity. Defining the traits that affect persistence is essential for improving pasture longevity through plant breeding and for identifying criteria that should be included in cultivar ranking indices. Compared with a conventional longitudinal study (a single study monitored over time), repeated annual sowings allow the effects on persistence of sowing year and the ensuing interactions between environment and age of pasture to be identified. An experiment commenced in 2016 in Waikato, in which eight cultivars of perennial ryegrass representing different ploidy, flowering date, and cultivar age, and one each of tall fescue and cocksfoot were sown each autumn in a randomised complete block design with four replicates in autumn 2016, spring 2017 and autumn 2018. This paper reports interim data on pasture yield, composition and density in the autumn following each sowing, and for the 2018 sowing only, in the 6 months after sowing. For the three successive autumn measurements there were significant effects due to cultivar, year of sowing and their interactions for all pasture variables. These differences in establishment may have consequences for the future resilience of these pastures under natural biotic and abiotic stressors.

Effect of deferred grazing during late spring and summer on pasture productivity in Waikato and Bay of Plenty hill country

Deferred grazing is a commonly used tool to manage feed surpluses. The effect of deferred grazing on pasture nutritive value and productivity was quantified in a split-paddock trial on three hill country farms in Waikato and Bay of Plenty from October 2018 until May 2020. Livestock were excluded from the deferred pasture between mid-October 2018 and March 2019. Thereafter, both treatments were rotationally grazed in common with cattle or sheep depending on the farm. Total annual dry matter production was 15% greater in the deferred than grazed treatment for the 12 months after deferring (8.9 vs 7.7 t DM/ha, P<0.05). Metabolisable energy (ME) values at the end of the deferred period were lower in the deferred than grazed treatment (P<0.01) but similar in both treatments thereafter. The content of legumes other than white clover (Trifolium repens) was higher in deferred than grazed pastures in spring 2019 on one of the farms (treatment × farm interaction P<0.05). Ground cover of perennial ryegrass was greater and the area of bare ground smaller, in the deferred than grazed treatment on three of five occasions from after the beginning of the deferred period until up to 8 months after deferring (P<0.05). There was no difference between treatments in decomposition and stabilisation of organic matter (P>0.05). The topsoil water content was higher in the deferred than grazed treatment for 12 months after deferring. In comparison to regular grazing between October and March, deferred pastures provided drought feed in autumn 2019. Pasture productivity was increased after the deferred period without negative impacts on ME.

Identifying morphological traits associated with vegetative persistence in the perennial ryegrass (Lolium perenne L.) cultivar 'Grasslands Samson'

Perennial ryegrass (Lolium perenne L.) vegetative persistence (maintained herbage growth and survival without reseeding) is an important economic trait for farmers in New Zealand as it decreases the frequency of reseeding pastures. Vegetative persistence is difficult to breed for due to a lack of long-term trials to observe the complex interactions between plant genotype and the environment. In a long-term trial a genetic shift in the sown cultivar population could occur as individual plants with advantageous traits outcompete other plants and survive. The objectives of our study were to investigate the occurrence of a potential genetic shift in a sample (30 plants) of a persistent population of ‘Grasslands Samson’ perennial ryegrass. Persistent plants were collected from a nine-year-old trial at Poukawa, Hawke's Bay. To identify a genetic shift, these plants were compared to a sample of 30 plants sourced from commercial seed of ‘Grasslands Samson’ representing the original population. This study estimated genotypic variation within and between the populations for eight morphological traits after 10 weeks' growth under glasshouse conditions. Phenotypic and genotypic correlations between the traits were estimated. Results showed that the persistent population had significantly (P<0.05) greater means for tiller number, reproductive tiller number, lamina sheath length, and dry weight. Future research studying these traits across farm environments would further understanding of their roles in vegetative persistence of ryegrass.