Appendix 1 to Environmental Benchmarks for Arable Crop Production Project ES0112
1 Introduction 4
1.1 Drivers for environmental change in arable agriculture 4
1.2 Benchmarks for environmental change 4
1.3 Regional differences 4
1.4 The Benchmarking Process 5
1.5 MEASURES 5
1.6 Aims and Objectives 6
2 Method 6
2.1 How MEASURES works and what it does 6
2.1.1 The long term 7
2.1.2 Soil, rain and crop interactions. 7
2.1.3 Optimal timing 7
2.1.4 Mixed farms 8
2.1.5 The N cycle, P and K 8
2.1.6 Rotational N transfers 9
2.1.7 N losses 9
2.1.8 The overall balance 10
2.1.9 P & K 10
2.1.10 Reprise 10
2.2 Improvements to MEASURES since the original report 10
2.2.1 Reconciliation of N balances at the rotational level 11
2.2.2 Grass production and environmental emissions 11
2.2.3 Partitioning of leaching and denitrification from arable crops 12
2.2.4 Improved emission terms from animal husbandry for ammonia, methane and nitrous oxide 13
2.2.5 A Revised soil erosion equation, incorporating a variable slope term 16
2.2.6 Determination of pesticide inputs 16
2.3 Regions and current arable practices 17
2.3.1 Definitions of Regions 17
2.4 Regional spatial data gathering and processing 20
2.4.1 Rain 20
2.4.2 Reasons for excluding certain 5 km grid squares and soil angles. 22
2.4.3 Soils 23
2.4.4 Slope 26
2.4.5 Summary of regional physical properties 27
2.5 Running MEASURES to produce a regional farm 27
2.6 Definitions of farm types 28
2.6.1 Appropriate farm sizes 28
2.6.2 Farm enterprises 29
2.6.3 Appropriate stocking rates 32
2.7 Current Practices 34
2.7.1 Critical practices and regional variation 39
3 Results 42
3.1 Validation & Benchmarking 42
3.1.1 Predicted cropping patterns 42
3.2 Predicted environmental outcome - The Benchmarks 46
3.2.1 Baseline combineable only arable 46
3.2.2 Roots vs. combineable only 46
3.2.3 Combineable and potatoes only 47
3.2.4 Dairy Error! Bookmark not defined.
3.2.5 Pigs 48
3.2.6 Broilers 49
3.2.7 Iso-nitrogenous excretory loadings from livestock 50
3.2.8 Sectorial and regional differences 51
3.2.9 Combinable cropping farm type 52
3.2.10 Combinable with root cropping farm type 54
3.2.11 Combinable with root cropping (no Potatoes) farm type 56
3.2.12 Combinable cropping with dairy farm type, 200 head plus followers on 300ha 57
3.2.13 Combinable cropping with dairy farm type, 100 head plus followers on 300ha 58
3.2.14 Combinable cropping with dairy farm type, 200 head plus followers on 300ha, No Maize 59
3.2.15 Combinable cropping with pigs farm type, 1500 pig places on 300ha 60
3.2.16 Combinable cropping with pigs farm type, 500 pig places on 300ha 61
3.2.17 Combinable cropping with pigs farm type, 2500 pig places on 300ha 62
3.2.18 Combinable cropping with pigs farm type, 1560 pig places on 300ha 63
3.2.19 Combinable cropping with broilers farm type, 50,000 broiler places on 300ha 64
3.2.20 Combinable cropping with broilers farm type, 100,000 broiler places on 300ha 65
3.2.21 Combinable cropping with broilers farm type, 200,000 broiler places on 300ha 66
3.2.22 Combinable cropping with broilers farm type, 70,000 broiler places on 300ha 67
3.2.23 Combinable cropping with pigs farm type, weighted average stocking on 300ha 68
3.2.24 Combinable cropping with broilers farm type, weighted average stocking on 300ha 69
3.3 Evaluation of [future] improved practices 70
3.3.1 Delaying Ploughing for spring crops until the New Year 70
3.3.2 Winter crops established by 4th November 71
3.3.3 Sown cover cropping 71
3.3.4 Restricted winter cropping 71
3.3.5 Minimum tillage 71
4 Discussion 74
5 Conclusions 75
6 References 75
24487
Appendix 1 ES0112 - 48 -
1 Introduction
1.1 Drivers for environmental change in arable agriculture
A range of current and future international agreements and EU directives exist to control or reduce a range of environmental burdens to land air and water:
· EU Nitrates Directive
o Protects drinking water and waters vulnerable to eutrophication (estuarine and coastal) from nitrate pollution.
· The Kyoto protocol
o Limits greenhouse gas emission
· Integrated Pollution Prevention and Control
o Limits emission, especially ammonia, from large pig and poultry facilities
· National Emissions Ceilings Directive
o Limits ammonia emission from agriculture
· EU Water Framework Directive
o Limits the loss of Phosphorus to water vulnerable to eutrophication and integrates with the Nitrate Directive
Before progress in achieving environmental impact reduction can be assessed, we need to quantify the present state, set achievable objectives as targets and have the means of measuring progress towards these targets. Defra has a set of indicators that will help towards this but some assessment of what really happens on farms is needed to provide a benchmark against which to measure change. Benchmarking arable agriculture was the highest rated research priority in the Defra project “Scoping study to identify new research opportunities in the area of arable crops and environmental interactions” (IS0103)
1.2 Benchmarks for environmental change
In order to implement environmental change, it is necessary to quantify the environmental burdens that currently arise from arable crop production and to use these measures as benchmarks or baselines against which change can be explored and measured.
The main environmental measures that are required are:
· Nutrient pollution in the form of nitrates and phosphates
· Greenhouse gases, such as methane and nitrous oxide
· Ammonia
1.3 Regional differences
Current arable practice varies between geographical regions of England and Wales. This is partly a result of weather and soil combinations, which will favour some crops over others, as
well as different traditional approaches to farming, the size of each farm and the blend of arable and animal enterprises. Other factors may influence crop choice, e.g. the proximity of a sugar beet processing factory as well as quota to grow sugar beet as well as special equipment for harvesting certain crops (e.g. potatoes). In all cases, there will be a level of crop production and associated environmental burdens. These will vary with climatic region and soil type, so that a unit mass of wheat grown on thin soil over chalk or limestone in a wetter part of the UK is likely to be associated with more nitrate leaching that the same crop on a deep loam in a drier part of the UK
Emissions and crop output will also be influenced by factors, such as the use of manures (and the allowance made for its nutrients) together with external constraints, like Nitrate Vulnerable Zones (NVZs) and Integrated Pollution Prevention and Control (IPPC). Emissions from arable crops with manure (and hence less mineral fertiliser) must be balanced against emissions from arable crops with more fertiliser. Manure and manurial crops, as sources of fertiliser for arable crops, have largely been replaced by mineral fertilisers, because (a) there is insufficient and (b) mineral fertilisers are more reliable and les liable to losses, such as ammonia volatilisation and nitrate leaching. Nevertheless, where manure does exist, it is a valuable fertiliser and soil improver as much as a waste product of animal production and is a major contributor to recycling.
There are many alternative practices that could be considered to improve agricultural efficiency and/ or reduce environmental burdens. Not all will work for all circumstances and not all generate reduced emissions per unit of functional output, e.g. 1 kgwheat.
1.4 The Benchmarking Process
Benchmarking, as a process, is a method of comparative analysis where one set of measures is compared to another. The difference identifies areas where improvement could be or have been made. The process is iterative and interactive, working as an action learning cycle. Benchmarking can also bring many benefits by encouraging critical thinking about the situation, finding out what is really important and how it is done.
An important feature of the benchmarking process is the ability to investigate the differences between systems in a manner that allows you to determine the mechanistic explanation as to how an improvement can be achieved or what is causing the problem. In agriculture, many comparative data are averages and, as such, represent systems that do not literally exist and are, thus, of limited use in determining what should be done differently.
1.5 MEASURES
The MEASURES (Multiple Environmental Outcomes from Agricultural Systems) project (WA0801) had produced a framework to evaluate farm practise to meet multiple environmental objectives. This is a whole farm systems model (Audsley, 1981). It allows different farming practices to be examined in terms of both impacts on yield and the costs of production as well as on the environment (including emissions to air and water of ammonia, nitrous oxide, methane, nitrate and phosphate).
The core of the MEASURES model is the Silsoe Whole Farm Model (SWFM), with its detailed database of crop options, interactions, inputs, labour and machinery requirements as functions of soil type, climate and level of intensification (Annetts and Audsley, 2002). Detailed relationships describing environmental burdens have been added to it, making allowances for the need to consider a long-term steady state for true sustainability. These have been derived from process models (e.g. SUNDIAL, Smith et al., 1996) that simulate environmental processes as well as from national inventories.
The MEASURES model can both quantify the current state of a wide variety of farms with respect to multiple environmental objectives, economics and labour and predict the impact on farms of setting new targets. The MEASURES model is, thus, a very suitable tool to use to quantify environmental benchmarks for regionally distinct farming systems and to permit the
mechanistic investigation of the systemic causes of the environmental-burdens of arable farming.
1.6 Aims and Objectives
The main purpose of this project is to quantify the baseline emissions associated with arable production per unit of functional output as it is now and with improved techniques. Defra and other stakeholders will, thus, be informed about the current levels of emissions and the likely impact of different agricultural practices on the environment and overall sustainability.
The individual objectives are:
1. Define current arable practices in regions of England and Wales (excepting organic systems)
2. Evaluate current practices on a regional basis with the MEASURES framework in terms of burdens, crop outputs and interactions
3. Define improved practices that could be utilised by farmers at little or no extra cost to themselves
4. Evaluate future practices with MEASURES framework in terms of burdens, crop outputs and interactions.
This approach will quantify any environmental benefits of new farm practices and help prioritise research and development into new farm practices
The main body of the report is laid out using the above four objectives.
2 Method
Appendix 1 ES0112 - 48 -
2.1 How MEASURES works and what it does
MEASURES takes the definition of a whole farm, which is described in a set of equations and information in databases, and calculates the most profitable cropping rotation for that farm. It also calculated a variety of environmental burdens from that farm as well as indicators, such as the soil phosphate balance. The farm may be arable only or mixed and the animal enterprise can be housed-only livestock (e.g. finishing pigs) or grazing animals with forage requirements.
A farm is principally described in terms of area, soil texture (one only per farm), rainfall and animal types and numbers. The user can specify a selection of crops, each of which has a set of time-bound cultivation requirements that require inputs of labour, machinery, fertilisers, pesticides etc. Each crop is defined by a growth equation, which links yield to the input of N fertiliser (essentially N) and rainfallsoil texture. Yield and /or cost penalties are applied if a crop is established too late [or too early?] and if cereals [or any other crops?] are grown in successive years. Various rules determine the level of penalty and some crop successions are prohibited to minimise disease transfer. If grazing livestock are included, part of the farm must provide the forage component of their diet. Manure from all livestock is applied to the land and nutrients contained therein are accounted for within the estimation of fertiliser requirements. The model finds the best optimum plan by for the farm by maximising the whole farm net profit (all farm income minus the costs of inputs, labour and machinery – it does include general farm overheads or rent)[defined as …]. Within this process, it assimilates the costs of all inputs for the possible crops, the timings and time taken for each operation together with yields as affected by non-optimal activities. This process also calculates the actual inventory and labour requirements for the whole farm. The process of optimisation is achieved with linear programming.
Figure 1
The long term
MEASURES, like the Silsoe Whole Farm Model, analyses farm with a long term view, which requires operating in a steady state manner. This is manifested, for example, by the N balance being maintained over a whole rotation, although variations in soil N status may be inferred within a rotation. Am implication of this is that we oblige all N losses to reach the environment, rather than being locked up in short or medium term soil pools. This can cause emissions like nitrate leaching to be a bit larger than is normally expected. The philosophy behind this is that organic N (e.g. from crop debris or manure) will eventually be mineralised and partitioned between useful crop offtake and wastage by denitrification or leaching (Appendix 1).
Soil, rain and crop interactions.
Crop yields depend on soil texture and, in the case of grass, on rainfall. Soil texture is defined by a numerical index (0.5 to 2.5) representing the range of textures from sandy to heavy clay and yields increase with the soil index, because the water retentiveness increases, so supporting better growth in the summer. Working heavier soils, however, require more effort in terms of time and fuel than lighter ones. The hours that a soil is workable decreases as soil index and rainfall increases. The extra flexibility and economy in cultivation given by a lighter soil is thus offset by lower revenue from reduced yields.
Optimal timing
There is an optimum time to establish a crop in terms of profitability (fig x). Premature establishment reduces yield by disease and late establishment reduce yield through a shortage of light and growing time (and possibly poorer germination in winter crops). Establishing all of a crop at the ideal time for maximum yield requires a large input of labour and machinery and so would increase the cost, while spreading out the time of establishment will reduce both yield and costs and this usually provides the optimum approach (Fig x). Most operations are time-bound within seasonal windows and some must fit into particular sequences, e.g. drilling must follow cultivation. Additional constraints, like NVZ regulations, can impose restrictions on the timings or duration of operations, e.g. manure spreading. Since these operations are time-bound, the constraints will impose a stress on the whole farm system. A consequence is likely to be a change in the crop rotation to accommodate the constraint. This is a particular strength of the whole farm approach as apparently counter-intuitive responses can result from it with good reason.