• The Complex Pathway towards Farm-Level Sustainable Intensification: An Exploratory Network Analysis of Stakeholders’ Knowledge and Perception

      Micha, Evgenia; Fenton, Owen; Daly, Karen M.; Kakonyi, Gabriella; Ezzati, Golnaz; Moloney, Thomas; Thornton, Steven; European Union; 675120 (MDPI AG, 2020-03-25)
      Farm-level sustainable intensification of agriculture (SIA) has become an important concept to ensuring food security while minimising negative externalities. However, progress towards its achievement is often constrained by the different perceptions and goals of various stakeholders that affect farm management decisions. This study examines farm-level SIA as a dynamic system with interactive components that are determined by the interests of the stakeholders involved. A systems thinking approach was used to identify and describe the pathways towards farm-level SIA across the three main pillars of sustainability. An explanatory network analysis of fuzzy cognitive maps (FCMs) that were collectively created by representative groups of farmers, farm advisors and policy makers was performed. The study shows that SIA is a complex dynamic system, affected by cognitive beliefs and particular knowledge within stakeholder groups. The study concludes that, although farm-level SIA is a complex process, common goals can be identified in collective decision making.
    • Ecosystem function enhanced by combining four functional types of plant species in intensively-managed grassland mixtures: a three-year continental-scale field experiment

      Finn, John; Kirwan, Laura; Connolly, John; Sebastia, Maria Teresa; Helgadottir, Aslaug; Baadshaug, Ole; Belanger, Gilles; Black, Alistair D; Brophy, C.; Collins, Rosemary; et al. (Wiley-Blackwell, 22/02/2013)
      1. A co-ordinated continental-scale field experiment across 31 sites was used to compare the biomass yield of monocultures and four-species mixtures associated with intensively managed agricultural grassland systems. To increase complementarity in resource use, each of the four species in the experimental design represented a distinct functional type derived from two levels of each of two functional traits, nitrogen acquisition (N2-fixing legume or non-fixing grass) crossed with temporal development (fast-establishing or temporally persistent). Relative abundances of the four functional types in mixtures were systematically varied at sowing to vary the evenness of the same four species in mixture communities at each site, and sown at two levels of seed density. 2. Across multiple years, the total yield (including weed biomass) of the mixtures exceeded that of the average monoculture in >97% of comparisons. It also exceeded that of the best monoculture (transgressive overyielding) in about 60% of sites, with a mean yield ratio of mixture to best-performing monoculture of 1.07 across all sites. Analyses based on yield of sown species only (excluding weed biomass) demonstrated considerably greater transgressive overyielding (significant at about 70% of sites, ratio of mixture to best-performing monoculture = 1.18). 3. Mixtures maintained a resistance to weed invasion over at least three years. In mixtures, median values indicate <4% of weed biomass in total yield, whereas the median percentage of weeds in monocultures increased from 15% in year 1 to 32% in year 3. 4. Within each year, there was a highly significant relationship (P<0.0001) between sward evenness and the diversity effect (excess of mixture performance over that predicted from the monoculture performances of component species). At lower evenness values, increases in community evenness resulted in an increased diversity effect, but the diversity effect was not significantly different from the maximum diversity effect across a wide range of higher evenness values. The latter indicates the robustness of the diversity effect to changes in species’ relative abundances. 5. Across sites with three complete years of data (24 of the 31 sites), the effect of interactions between the fast-establishing and temporal persistent trait levels of temporal development was highly significant and comparable in magnitude to effects of interactions between N2-fixing and non-fixing trait levels of nitrogen acquisition. 6. Synthesis and applications. The design of grassland mixtures is relevant to farm-level strategies to achieve sustainable intensification. Experimental evidence indicated significant yield benefits of four-species agronomic mixtures which yielded more than the highest-yielding monoculture at most sites. The results are relevant for agricultural practice, and show how grassland mixtures can be designed to improve resource complementarity, increase yields and reduce weed invasion. The yield benefits were robust to considerable changes in the relative proportions of the four species, which is extremely useful for practical management of grassland swards.
    • The Effect of Chemical Amendments Used for Phosphorus Abatement on Greenhouse Gas and Ammonia Emissions from Dairy Cattle Slurry: Synergies and Pollution Swapping

      Brennan, Raymond B.; Healy, Mark G.; Fenton, Owen; Lanigan, Gary; European Union; Teagasc Walsh Fellowship Programme; FP7-KBBE-2010-4 (PLoS, 08/06/2015)
      Land application of cattle slurry can result in incidental and chronic phosphorus (P) loss to waterbodies, leading to eutrophication. Chemical amendment of slurry has been proposed as a management practice, allowing slurry nutrients to remain available to plants whilst mitigating P losses in runoff. The effectiveness of amendments is well understood but their impacts on other loss pathways (so-called ‘pollution swapping’ potential) and therefore the feasibility of using such amendments has not been examined to date. The aim of this laboratory scale study was to determine how the chemical amendment of slurry affects losses of NH3, CH4, N2O, and CO2. Alum, FeCl2, Polyaluminium chloride (PAC)- and biochar reduced NH3 emissions by 92, 54, 65 and 77% compared to the slurry control, while lime increased emissions by 114%. Cumulative N2O emissions of cattle slurry increased when amended with alum and FeCl2 by 202% and 154% compared to the slurry only treatment. Lime, PAC and biochar resulted in a reduction of 44, 29 and 63% in cumulative N2O loss compared to the slurry only treatment. Addition of amendments to slurry did not significantly affect soil CO2 release during the study while CH4 emissions followed a similar trend for all of the amended slurries applied, with an initial increase in losses followed by a rapid decrease for the duration of the study. All of the amendments examined reduced the initial peak in CH4 emissions compared to the slurry only treatment. There was no significant effect of slurry amendments on global warming potential (GWP) caused by slurry land application, with the exception of biochar. After considering pollution swapping in conjunction with amendment effectiveness, the amendments recommended for further field study are PAC, alum and lime. This study has also shown that biochar has potential to reduce GHG losses arising from slurry application.
    • Effects of multi-species swards on dry matter production and the incidence of unsown species at three Irish sites

      Connolly, John; Finn, John; Black, Alistair D; Kirwan, Laura; Brophy, C.; Luscher, A.; European Union; Science Foundation Ireland; COST Action 852; 09/RFP/EOB2546 (Teagasc (Agriculture and Food Development Authority), Ireland, 2009)
      Recent ecological research provides evidence that an increased number of plant species in natural grasslands is associated with increased biomass productivity, and provides a wide range of other ecosystem benefits. This suggests that increases in species diversity in agricultural ecosystems may similarly lead to increased benefits. The work reported below was part of the COST 852 Agrodiversity experiment, carried out at 34 sites across Europe. In Ireland, the effects of four-species grass-clover mixtures on herbage production, species persistence and unsown species suppression at three sites over multiple years, were investigated under growing conditions that were intensive relative to unfertilised natural grassland systems. The design included a range of four-species mixtures and monocultures of perennial ryegrass, timothy, cocksfoot, white clover, red clover and Caucasian clover. Several harvests were taken at each site for two or three years. Species diversity had a strong, persistent and positive effect on overall yield and the yield of sown species, and enhanced resistance to the growth of unsown species. Mixtures generally yielded well when compared with the best monoculture, and sometimes out yielded it. These effects on total yield declined over time but were still important at the end of the experiments. The diversity effects on sown species yield and on resistance to unsown species increased with time. Diversity effects were robust to changes in species composition, and persisted for the duration of the experiments across mixtures and over time. Virtually every mixture had a higher yield, and suppressed unsown species better, than monocultures of perennial ryegrass. These patterns were broadly consistent across sites. The persistence of species varied widely and was not consistent across sites.
    • A Field-Scale Decision Support System for Assessment and Management of Soil Functions

      Debeljak, Marko; Trajanov, Aneta; Kuzmanovski, Vladimir; Schröder, Jaap; Sandén, Taru; Spiegel, Heide; Wall, David; Van de Broek5, Marijn; Rutgers, Michiel; Bampa, France; et al. (Frontiers Media SA, 2019-08-05)
      Agricultural decision support systems (DSSs) are mostly focused on increasing the supply of individual soil functions such as, e.g., primary productivity or nutrient cycling, while neglecting other important soil functions, such as, e.g., water purification and regulation, climate regulation and carbon sequestration, soil biodiversity, and habitat provision. Making right management decisions for long-term sustainability is therefore challenging, and farmers and farm advisors would greatly benefit from an evidence-based DSS targeted for assessing and improving the supply of several soil functions simultaneously. To address this need, we designed the Soil Navigator DSS by applying a qualitative approach to multi-criteria decision modeling using Decision Expert (DEX) integrative methodology. Multi-criteria decision models for the five main soil functions were developed, calibrated, and validated using knowledge of involved domain experts and knowledge extracted from existing datasets by data mining. Subsequently, the five DEX models were integrated into a DSS to assess the soil functions simultaneously and to provide management advices for improving the performance of prioritized soil functions. To enable communication between the users and the DSS, we developed a user-friendly computer-based graphical user interface, which enables users to provide the required data regarding their field to the DSS and to get textual and graphical results about the performance of each of the five soil functions in a qualitative way. The final output from the DSS is a list of soil mitigation measures that the end-users could easily apply in the field in order to achieve the desired soil function performance. The Soil Navigator DSS has a great potential to complement the Farm Sustainability Tools for Nutrients included in the Common Agricultural Policy 2021–2027 proposal adopted by the European Commission. The Soil Navigator has also a potential to be spatially upgraded to assist decisions on which soil functions to prioritize in a specific region or member state. Furthermore, the Soil Navigator DSS could be used as an educational tool for farmers, farm advisors, and students, and its potential should be further exploited for the benefit of farmers and the society as a whole.
    • Functional Land Management: Bridging the Think-Do-Gap using a multi-stakeholder science policy interface

      O'Sullivan, Lilian; Wall, David; Creamer, Rachel E.; Bampa, Francesca; Schulte, Rogier P.; European Union; National Development Plan 2007–2013.; 635201; 677407; 13S468 (Springer, 2017-11)
      Functional Land Management (FLM) is proposed as an integrator for sustainability policies and assesses the functional capacity of the soil and land to deliver primary productivity, water purification and regulation, carbon cycling and storage, habitat for biodiversity and recycling of nutrients. This paper presents the catchment challenge as a method to bridge the gap between science, stakeholders and policy for the effective management of soils to deliver these functions. Two challenges were completed by a wide range of stakeholders focused around a physical catchment model—(1) to design an optimised catchment based on soil function targets, (2) identify gaps to implementation of the proposed design. In challenge 1, a high level of consensus between different stakeholders emerged on soil and management measures to be implemented to achieve soil function targets. Key gaps including knowledge, a mix of market and voluntary incentives and mandatory measures were identified in challenge 2.
    • The Impact of Policy Instruments on Soil Multifunctionality in the European Union

      Vrebos, Dirk; Bampa, Francesca; Creamer, Rachel E.; Gardi, Ciro; Ghaley, Bhim Bahadur; Jones, Arwyn; Rutgers, Michiel; Sandén, Taru; Staes, Jan; Meire, Patrick; et al. (MDPI, 2017-03-09)
      Agricultural ecosystems provide a range of benefits that are vital to human well-being. These benefits are dependent on several soil functions that are affected in different ways by legislation from the European Union, national, and regional levels. We evaluated current European Union soil-related legislation and examples of regional legislation with regard to direct and indirect impacts on five soil functions: the production of food, fiber, and fuel; water purification and regulation; carbon sequestration and climate regulation; habitat for biodiversity provisioning; and the recycling of nutrients/agro-chemicals. Our results illustrate the diversity of existing policies and the complex interactions present between different spatial and temporal scales. The impact of most policies, positive or negative, on a soil function is usually not established, but depends on how the policy is implemented by local authorities and the farmers. This makes it difficult to estimate the overall state and trends of the different soil functions in agricultural ecosystems. To implement functional management and sustainable use of the different soil functions in agricultural ecosystems, more knowledge is needed on the policy interactions as well as on the impact of management options on the different soil functions.
    • Methodological tests of the use of trace elements as tracers to assess root activity

      Hoekstra, Nyncke J.; Finn, John; Buchmann, Nina; Gockele, A.; Landert, L.; Prill, N.; Scherer-Lorenzen, M.; Luscher, L.; European Union; Irish Research Council; et al. (Springer, 2014-03)
      Background and aims There is increasing interest in how resource utilisation in grassland ecosystems is affected by changes in plant diversity and abiotic conditions. Research to date has mainly focussed on aboveground responses and there is limited insight into belowground processes. The aim of this study was to test a number of assumptions for the valid use of the trace elements caesium, lithium, rubidium and strontium as tracers to assess the root activity of several grassland species. Methods We carried out a series of experiments addressing the reliability of soil labelling, injection density, incubation time, application rate and the comparability of different tracers in a multiple tracer method. Results The results indicate that it is possible to achieve a reliable labelling of soil depths. Tracer injection density affected the variability but not the mean level of plant tracer concentrations. Tracer application rates should be based on pilot studies, because of site- and species-specific responses. The trace elements did not meet prerequisites to be used in a multiple tracer method. Conclusions The use of trace elements as tracers is potentially a very useful tool to give insight into plant root activity at different soil depths. This work highlights some of the main benefits and pitfalls of the method and provides specific recommendations to assist the design of tracer experiments and interpretation of the results.
    • Multiple factors control the environmental effectiveness of agri-environment schemes: implications for design and evaluation

      Finn, John; Kurz, Isabelle; Bourke, David; European Union; European Commission; SSPE-CT-2003-502070 (School of Agriculture, Food Science and Veterinary Medicine, University College Dublin in association with Teagasc, 2008)
      Achieving and evaluating the environmental effectiveness of agri-environment schemes (AESs) has proven difficult. The design and ex ante evaluation of AESs is a crucial phase for ensuring effectiveness, but seems to receive relatively little attention. We propose a programme theory (a structured description of the various cause-and-effect relationships that underpin and achieve a policy initiative) for AESs that considers multiple factors that drive environmental performance at farm-scale (appropriate farm-level objectives, farmer compliance, implementation by institutions, and cause-and-effect relationship between management prescriptions and environmental objectives), and factors that determine how farm-scale performance aggregates to produce scheme-scale performance (participation rate, targeting, and threshold effects). These factors can be used as assessment criteria with which to pinpoint specific causes of AES failure, and thereby offer a practical approach to complement the design and evaluation of the environmental effects of AESs.
    • Nitrogen yield advantage from grass-legume mixtures is robust over a wide range of legume proportions and environmental conditions

      Suter, Matthias; Connolly, John; Finn, John; Loges, R.; Kirwan, Laura; Sebastia, Maria Teresa; Luscher, A.; European Union (Wiley, 28/01/2015)
      Current challenges to global food security require sustainable intensification of agriculture through initiatives that include more efficient use of nitrogen (N), increased protein self-sufficiency through home-grown crops, and reduced N losses to the environment. Such challenges were addressed in a continental-scale field experiment conducted over three years, in which the amount of total nitrogen yield (Ntot) and the gain of N yield in mixtures as compared to grass monocultures (Ngainmix) was quantified from four-species grass-legume stands with greatly varying legume proportions. Stands consisted of monocultures and mixtures of two N2 fixing legumes and two non-fixing grasses.The amount of Ntot of mixtures was significantly greater (P ≤ 0.05) than that of grass monocultures at the majority of evaluated sites in all three years. Ntot and thus Ngainmix increased with increasing legume proportion up to one third of legumes. With higher legume percentages, Ntot and Ngainmix did not continue to increase. Thus, across sites and years, mixtures with one third proportion of legumes attained ~95% of the maximum Ntot acquired by any stand and had 57% higher Ntot than grass monocultures.Realized legume proportion in stands and the relative N gain in mixture (Ngainmix/Ntot in mixture) were most severely impaired by minimum site temperature (R = 0.70, P = 0.003 for legume proportion; R = 0.64, P = 0.010 for Ngainmix/Ntot in mixture). Nevertheless, the relative N gain in mixture was not correlated to site productivity (P = 0.500), suggesting that, within climatic restrictions, balanced grass-legume mixtures can benefit from comparable relative gains in N yield across largely differing productivity levels.We conclude that the use of grass-legume mixtures can substantially contribute to resource-efficient agricultural grassland systems over a wide range of productivity levels, implying important savings in N fertilizers and thus greenhouse gas emissions and a considerable potential for climate change mitigation.
    • Risk Assessment of E. coli Survival Up to the Grazing Exclusion Period After Dairy Slurry, Cattle Dung, and Biosolids Application to Grassland

      Ashekuzzaman, S.M.; Richards, Karl G.; Ellis, Stephanie; Tyrrel, Sean; O'Leary, Emma; Griffiths, Bryan; Ritz, Karl; Fenton, Owen; European Union; 265269 (Frontiers in Sustainable Food Systems, 10/07/2018)
      Grassland application of dairy slurry, cattle dung, and biosolids offers an opportunity to recycle valuable nutrients (N, P, and K), which may all introduce pathogens to the soil environment. Herein, a temporal risk assessment of the survival of Escherichia coli (E. coli) up to 40 days in line with the legislated grazing exclusion time points after application was examined across six scenarios: (1) soil and biosolids mixture, (2) biosolids amended soil, (3) dairy slurry application, (4) cattle dung on pasture, (5) comparison of scenario 2, 3, and 4, and (6) maximum legal vs. excess rate of application for scenario 2 and 3. The risk model input parameters were taken or derived from regressions within the literature and an uncertainty analysis (n = 1,000 trials for each scenario) was conducted. Scenario 1 results showed that E. coli survival was higher in the soil/biosolids mixture for higher biosolids portion, resulting in the highest 20 day value of residual E. coli concentration (i.e., C20, log10 CFU g−1 dw) of 1.0 in 100% biosolids or inoculated soil and the lowest C20 of 0.098 in 75/25 soil/biosolids ratio, respectively, in comparison to an average initial value of 6.4 log10 CFU g−1 dw. The E. coli survival across scenario 2, 3, and 4 showed that the C20 value of biosolids (0.57 log10 CFU g−1 dw) and dairy slurry (0.74 log10 CFU ml−1) was 2.9–3.7 times smaller than that of cattle dung (2.12 log10 CFU g−1 dw). The C20 values of biosolids and dairy slurry associated with legal and excess application rates ranged from 1.14 to 1.71 log10 CFU ha−1, which is a significant reduction from the initial concentration range (12.99 to 14.83 log10 CFU ha−1). The E. coli survival in un-amended soil was linear with a very low decay rate resulting in a higher C20 value than that of biosolids or dairy slurry. The risk assessment and uncertainly analysis showed that the residual concentrations in biosolids/dairy slurry applied soil after 20 days would be 45–57% lower than that of the background soil E. coli concentration. This means the current practice of grazing exclusion times is safe to reduce the risk of E. coli transmission into the soil environment.
    • Risk Assessment of E. coli Survival Up to the Grazing Exclusion Period After Dairy Slurry, Cattle Dung, and Biosolids Application to Grassland

      Ashekuzzaman, S.M.; Richards, Karl G.; Ellis, Stephanie; Tyrrel, Sean; O'Leary, Emma; Griffiths, Bryan; Ritz, Karl; Fenton, Owen; European Union; 265269 (Frontiers, 2018-07-10)
      Grassland application of dairy slurry, cattle dung, and biosolids offers an opportunity to recycle valuable nutrients (N, P, and K), which may all introduce pathogens to the soil environment. Herein, a temporal risk assessment of the survival of Escherichia coli (E. coli) up to 40 days in line with the legislated grazing exclusion time points after application was examined across six scenarios: (1) soil and biosolids mixture, (2) biosolids amended soil, (3) dairy slurry application, (4) cattle dung on pasture, (5) comparison of scenario 2, 3, and 4, and (6) maximum legal vs. excess rate of application for scenario 2 and 3. The risk model input parameters were taken or derived from regressions within the literature and an uncertainty analysis (n = 1,000 trials for each scenario) was conducted. Scenario 1 results showed that E. coli survival was higher in the soil/biosolids mixture for higher biosolids portion, resulting in the highest 20 day value of residual E. coli concentration (i.e., C20, log10 CFU g−1 dw) of 1.0 in 100% biosolids or inoculated soil and the lowest C20 of 0.098 in 75/25 soil/biosolids ratio, respectively, in comparison to an average initial value of ~6.4 log10 CFU g−1 dw. The E. coli survival across scenario 2, 3, and 4 showed that the C20 value of biosolids (0.57 log10 CFU g−1 dw) and dairy slurry (0.74 log10 CFU ml−1) was 2.9–3.7 times smaller than that of cattle dung (2.12 log10 CFU g−1 dw). The C20 values of biosolids and dairy slurry associated with legal and excess application rates ranged from 1.14 to 1.71 log10 CFU ha−1, which is a significant reduction from the initial concentration range (12.99 to 14.83 log10 CFU ha−1). The E. coli survival in un-amended soil was linear with a very low decay rate resulting in a higher C20 value than that of biosolids or dairy slurry. The risk assessment and uncertainly analysis showed that the residual concentrations in biosolids/dairy slurry applied soil after 20 days would be 45–57% lower than that of the background soil E. coli concentration. This means the current practice of grazing exclusion times is safe to reduce the risk of E. coli transmission into the soil environment.
    • Sustainability indicators for improved assessment of the effects of agricultural policy across the EU: Is FADN the answer?

      Kelly, Edel; Latruffe, Laure; Desjeux, Yann; Ryan, Mary; Uthes, Sandra; Diazabakanab, Ambre; Dillon, Emma; Finn, John; European Union; 613800 (Elsevier, 2018-06)
      Policy reform of the CAP and society’s expectations of agriculture have resulted in a growing need for improved information on the effectiveness of policy in achieving high-level objectives for more sustainable practice in agriculture. This is a high priority given its importance for consumers, public policy and private industry. Data collection programmes will need to adapt their scope if their information is to adequately address new information needs about high-level objectives. Assessment of sustainability at the farm level is hindered by the lack of data with which to derive appropriate, meaningful, and relevant indicators. This is particularly problematic for assessment of agricultural sustainability across the European Union (EU). Various databases exist at the EU scale regarding agricultural data sources and we identify one of these, the EU Farm Accountancy Data Network (FADN), as having considerable potential to assess farm-level sustainability at EU level. We critique several examples of published work that has attempted to assess agricultural sustainability using: FADN data alone; FADN data in combination with data from supplementary surveys, and; FADN data in combination with data from other EU databases. We conclude that the FADN would need to broaden its scope of data collection if it is to address the new information needs of policy, and we discuss the challenges in expanding FADN with a view towards wider farm-level assessment of sustainability. These include careful selection of indicators based on various criteria, the representativeness of the FADN, and the need to include new themes to address environmental, social, and animal welfare effects of policy.
    • Using machine learning to estimate herbage production and nutrient uptake on Irish dairy farms

      Nikoloski, Stevanche; Murphy, Philip; Kocev, Dragi; Džeroski, Sašo; Wall, David; Teagasc Walsh Fellowship Programme; European Union; 635201 (Elsevier for American Dairy Science Association, 2019-08-22)
      Nutrient management on grazed grasslands is of critical importance to maintain productivity levels, as grass is the cheapest feed for ruminants and underpins these meat and milk production systems. Many attempts have been made to model the relationships between controllable (crop and soil fertility management) and noncontrollable influencing factors (weather, soil drainage) and nutrient/productivity levels. However, to the best of our knowledge not much research has been performed on modeling the interconnections between the influencing factors on one hand and nutrient uptake/herbage production on the other hand, by using data-driven modeling techniques. Our paper proposes to use predictive clustering trees (PCT) learned for building models on data from dairy farms in the Republic of Ireland. The PCT models show good accuracy in estimating herbage production and nutrient uptake. They are also interpretable and are found to embody knowledge that is in accordance with existing theoretical understanding of the task at hand. Moreover, if we combine more PCT into an ensemble of PCT (random forest of PCT), we can achieve improved accuracy of the estimates. In practical terms, the number of grazings, which is related proportionally with soil drainage class, is one of the most important factors that moderates the herbage production potential and nutrient uptake. Furthermore, we found the nutrient (N, P, and K) uptake and herbage nutrient concentration to be conservative in fields that had medium yield potential (11 t of dry matter per hectare on average), whereas nutrient uptake was more variable and potentially limiting in fields that had higher and lower herbage production. Our models also show that phosphorus is the most limiting nutrient for herbage production across the fields on these Irish dairy farms, followed by nitrogen and potassium.
    • Using machine learning to estimate herbage production and nutrient uptake on Irish dairy farms

      Nikoloski, Stevanche; Murphy, Philip M.; Kocev, Dragi; Džeroski, Sašo; Wall, David; European Union; 635201 (Elsevier, 2019-08-22)
      Nutrient management on grazed grasslands is of critical importance to maintain productivity levels, as grass is the cheapest feed for ruminants and underpins these meat and milk production systems. Many attempts have been made to model the relationships between controllable (crop and soil fertility management) and noncontrollable influencing factors (weather, soil drainage) and nutrient/productivity levels. However, to the best of our knowledge not much research has been performed on modeling the interconnections between the influencing factors on one hand and nutrient uptake/herbage production on the other hand, by using data-driven modeling techniques. Our paper proposes to use predictive clustering trees (PCT) learned for building models on data from dairy farms in the Republic of Ireland. The PCT models show good accuracy in estimating herbage production and nutrient uptake. They are also interpretable and are found to embody knowledge that is in accordance with existing theoretical understanding of the task at hand. Moreover, if we combine more PCT into an ensemble of PCT (random forest of PCT), we can achieve improved accuracy of the estimates. In practical terms, the number of grazings, which is related proportionally with soil drainage class, is one of the most important factors that moderates the herbage production potential and nutrient uptake. Furthermore, we found the nutrient (N, P, and K) uptake and herbage nutrient concentration to be conservative in fields that had medium yield potential (11 t of dry matter per hectare on average), whereas nutrient uptake was more variable and potentially limiting in fields that had higher and lower herbage production. Our models also show that phosphorus is the most limiting nutrient for herbage production across the fields on these Irish dairy farms, followed by nitrogen and potassium.
    • Yield of temperate forage grassland species is either largely resistant or resilient to experimental summer drought

      Hofer, Daniel; Suter, Matthias; Haughey, Eamon; Finn, John; Hoekstra, Nyncke J.; Buchmann, Nina; Luscher, A.; European Union; 266018 (Wiley, 17/06/2016)
      1.Due to climate change, an increasing frequency and severity of drought events are expected to impair grassland productivity, particularly of intensively managed temperate grasslands. 2.To assess drought impacts, a common field experiment to manipulate precipitation was set up at three sites (two Swiss and one Irish) using monocultures and mixtures with two and four key forage species. Species differed in their functional traits: a shallow-rooted non-legume (Lolium perenne L.), a deep-rooted non-legume (Cichorium intybus L.), a shallow-rooted legume (Trifolium repens L.) and a deep-rooted legume (Trifolium pratense L.). A 9-week summer drought was simulated, and soil water status, above-ground biomass yield and plant nitrogen (N) limitation were compared to a rainfed control. 3.Based on soil water measurements, the drought induced severe stress at both Swiss sites and extreme stress at the Irish site. Under severe stress, the legumes were more drought resistant and showed an average change in above-ground biomass (CAB, compared to rainfed control) of only −8% and −24% (for the two Swiss sites), while the non-legumes had an average CAB of −51% and −68%. The lower resistance of non-legumes coincided with an apparent limitation of plant N, which further increased under drought. Under extreme drought (Irish site), growth nearly ceased with an average CAB of −85%. 4.During a 6-week post-drought period with adequate water supply (Swiss sites), formerly drought-stressed species were highly resilient and either attained (legumes) or clearly outperformed (non-legumes) the yield level of the rainfed controls. This outperformance coincided with post-drought reductions in N limitation in formerly drought-stressed species. As a result, aggregated over the drought and the post-drought periods, a negative drought impact was found only for the shallow-rooted L. perenne at one of the severely stressed sites. 5.Significant overyielding by multispecies mixtures was evident under rainfed control conditions (+38% across all three sites, P < 0·05) and was equally apparent under severe drought (+50%, P < 0·05). This overyielding was greatest in mixtures with approximately equal species proportions and was sufficiently large that drought-stressed mixtures at least attained the same yield as the average of the rainfed monocultures. Under extreme drought, growth almost ceased in monocultures and mixtures. 6.Synthesis and applications. Yields of selected species of intensively managed temperate grasslands are either resistant to a single severe drought or are highly resilient as soon as soil moisture levels recover after the drought event. However, these forage species seem unable to cope with an extreme drought event. Combining species in mixtures can compensate for yield reductions caused by severe drought and it offers a practical management tool to adapt forage production to climate change.