Saturday, 21 September 2013

Windbreak/Shelterbelt Design

Shelterbelt/Windbreak

Protecting your garden from the wind will increase productivity and decrease workload. Often overlooked, it should be one of the first things you consider when designing your garden or choosing a site. Wind can be a major suppressant of plant growth desiccating the soil and increasing the transpiration rates (water loss) of  plants considerably. Strong winds can cause soil erosion, damage to plants and deter beneficial winged insects.

This tree signifies a prevailing wind coming from the right side of the picture. The growth directly exposed to the wind has been suppressed.    

The advantages of a windbreak are many, however there are some disadvantages and if designed poorly one can create a bigger problem rather than finding a solution. So lets take a look at the potential problems first.
    Frosts
    Poorly designed windbreaks can encourage frosts and although generally are no problem during the winter as the plants have adapted protection, late spring frosts can be a problem for sensitive plants.
    On a cold night the air nearest the ground is colder than that up above. The wind mixes it up preventing the lower layer from reaching freezing point. Sheltered areas are at more risk of frost than exposed areas. A windbreak that stops wind completely can increase the risk of frost and may even do more damage than good to the land it is protecting. By thinning out the shelter belt as it develops we can provide enough air flow to prevent this.

    Root competition 
    The plants used within the shelter belt will obviously require their share of ground water and nutrients. The root system of certain trees can be prolific and extend way beyond the visible above ground spread. Care should be taken to avoid planting too close to the edge of the shelter belt especially if heavy demanding crops are the intended beneficiaries of the shelter belt. A good understanding of the root systems of the plants you are using can ensure that invasive and heavy feeding plants are kept away from the leeway edge. On larger sites the inside edge is sometimes used for road access thereby making use of the land that would otherwise give a poor return. 

    Pests and diseases
    Consideration should be given to the ecology of the windbreak and how this may affect the surrounding areas. Certain trees will attract insects and wildlife not necessarily beneficial to other plants and trees. For example, Prunus cerasifera - Myrobalan Plum makes a great windbreak tree, growing fast, tolerating drought and wind. However fruit  from these trees, if not collected, may provide breeding grounds for large populations of  fruit boring organisms, such as Grapholita funebrana (Plum Moth), to establish. Once established these organisms may spread  to all other Prunus spp. in the garden and surrounding areas.      

    Shading 
    Bear in mind the shadow the shelter belt will create when mature. The shadow cast, root competition and the space taken by the belt itself will use a considerable amount of viable land and this will need to be weighed up from the benefits gained from a shelter belt.

    As mentioned above, if designed well, these potential problems can be avoided leaving you with all the advantages of a windbreak such as
    • Protection of plants
    • Preventing/reducing, wind erosion
    • Reducing evaporation from the soil
    • Reducing transpiration from plants
    • Protecting buildings (reducing fuel and maintenance needs)
    • Providing habitat and increasing biodiversity 
    • Creating soil fertility 
    • Productive potential, food, fodder, fuel, biomass, mulch, timber etc
    • Ornamental value 
    • Moderating extreme temperatures 

    Design - Where to Start 

    Before establishing a windbreak or shelter belt it is important to make a thorough study of the local winds and to plot on a map the direction and strength of the winds.

    Observing the wind 
    Wind can flow from any direction from horizontal to vertical depending on the energy balance. Wind can also curve or even rotate, a tornado for example. The units of measurement for wind speed is normally km/hr (kilometres per hour). Direction of wind is determined as a bearing angle from N. It is sufficient to use the eight points of the compass as a basis for determination of wind direction. Wind direction is noted from where it approaches, not where it is heading. There are many different types of instruments that measure wind speed and direction. However, the most common instrument used is known as an anemometer. It consists of three cups on arms that can rotate measuring wind speeds based on rate of rotations and a vane which indicates the wind direction.

    Basic forms of estimating wind strength and direction.


    The movement of fast moving low clouds normally indicates the approximate direction of the wind. Fog also will move in the direction of the wind.
    Wind can raise dust and other light objects and therefore following this movement is yet another technique that can help you estimate the strength and direction of the wind. It also can reveal eddies created by objects as wind flows around them. The same technique applies for blowing snow but this normally requires higher wind speeds.

    If you are around a body of water, it is possible to observe surface flow of wind based on the changes in water texture or ripples. Relatively stronger winds will disturb the water surface causing ripples. This region of ripples or darker texture can be observed moving as the wind progresses.

    Signs and patterns to help you determine the direction of prevailing winds

    Often you will find higher vegetation such as trees and tall shrubs seemingly leaning in one direction as shown in the picture above. This neatly signals the occurrence of a prevailing wind. Weather vanes and Wind Socks are easily accessible tools for measuring wind direction

    Wind in mountainous areas  
    Wind traveling across a mountainous region will move in waves. When clear of obstruction the wind can continue its wave motion creating eddies in the open plains.


    Motion of wind blowing across mountainous terrain

    Design - Essential Points 

    Windbreaks can be effective on a small and large scale. They can be used for the temporary protection of annual crops and in this case can be as simple as a row of Helianthus tuberosum - Jerusalum artichoke planted to screen wind sensitive crop or they can be as complex as a multi-row perennial plantation of trees, shrubs ,herbs and ground covers to shield a broad acre plantation.
    • When considering windbreak or shelter belt planting, three zones can be recognized: the windward zone (from which the wind blows); the leeward zone (on the side where the wind passes); and the protected zone (that in which the effect of the windbreak or shelterbelt is felt)
    • A barrier should be established perpendicular to the direction of the prevailing wind for maximum effect. A checkerboard pattern is required when the winds originate from different directions. This applies mainly to broad acre sites.  
    • The effectiveness of the windbreak or shelter belt is influenced by its permeability. If it is dense, like a solid wall, the airflow will pass over the top of it and cause turbulence on the leeward side giving a comparatively limited zone of effective shelter  compared to the zone that a permeable shelter creates. 
    • Optimum permeability is 40 to 50 percent of open space, corresponding to a density of 50 to 60 percent in vegetation.
    • It is generally accepted that a windbreak or shelter belt protects an area over a distance up to its own height on the windward side and up to 20 times its height on the leeward side, depending on the strength of the wind.

    • Gaps in the barriers should be avoided as they tend to channel accelerated wind through causing damage. If a gap is needed for access then further shelter should be provided to mitigate the wind passing through the gap.  

    Design - Selection of tree and shrub species

    When selecting plant species for windbreaks or shelter belts, start by observing plants in your area that are in windy positions already. Look for healthiest specimens and if possible propagate from these specimens or obtain the same specie from a nearby nursery. 
    You may desire a larger diversity of plants within your design. When selecting plants the following characteristics should be sought:
     
     
    • Rapid growth
    • Straight stems
    • Wind firmness
    • Good crown formation
    • Deep root system, which does not spread into nearby fields
    • Resistance to drought
    • Desired phonological characteristics (leaves all year long or only part of the year).
    • Productivity: timber, fruits, nuts, medicine, biomass, fertility  



    Design - Layout of Plants 

    There are a number of different ways to build a Shelter belt. It is generally accepted that multiple rows of plants provide increased protection. If using multiple rows, there is greater opportunity to obtain significant amount of food and resources from  within the shelter belt as well as creating excellent habitat for a range of organisms many of which are beneficial allies to the gardener/farmer. 
    One method, pictured below, includes a windward row of small- med  wind-firm trees with row of taller trees behind on the leeward row.

    Windward Row 

    If the prevailing wind is blowing from the north then the windward row should be established first as the faster growing central trees will reduce light availability. The plants in this row need to be somewhat shade tolerant, fast growing and wind firm. Plants already growing in windy positions around your site should be first choice. A selection of nitrogen fixers, evergreens and wildlife plants should be selected. This layer needs to provide a lower screen for the higher canopied next layer so should consist of bushy trees and shrubs that fill out low to the ground.

    Suitable Plants for Windward Row
    Aronia melanocarpa - Black Chokeberry  


    Leeward  Row 

    The leeward row should consist of fast growing taller trees and include nitrogen fixers , conifer species and tree’s that sucker freely. This area can provide coppice wood for fence posts or fuel and consist of upper canopy fruit trees such as White Mulberry-Morus alba and Hackberry-Celtis occidentalis.      

    Possible species selection for a three row Windbreak/Shelter belt 






























     
    You can also find a good selection of suitable plants at the plants for a future database .


    Interested in Ecological methods of growing food? Check out our Upcoming Courses and Events



    Our plant and seed orders are coming in for Autumn delivery. If you would like to purchase some plants this year to avoid disappointment order early as we have limited stock available.



     Balkan Ecology Project Bio-Nursery 


    Sunday, 15 September 2013

    Plant Elements (Nutrients)

    Essential Elements

    There are seventeen elements known to be necessary for plants to complete their life cycle,  the essential elements.

    The Primary and Secondary Nutrients labelled in this diagram I collectively refer to as Macronutrients

    Of the seventeen essential elements, hydrogen (H), oxygen (O), and carbon (C) come from the air and water and are readily available.  Although nitrogen can also be found in the air, its gaseous form is not useable by plants.  Along with nitrogen, the rest of the elements are found in the soil.  Depending on the soil properties, however, some of these elements may be present but not in forms that are useable for plant use.   Still some soils may lack one or more of these elements.  

    When one or more of the essential elements is deficient, plants cannot complete their life cycle.  Such deficiency will be expressed in deformed plant growth and a supply of the lacking elements will need to be provided in order for the plant to survive.



    Macronutrients  

    Macronutrients are essential elements that are required by the plants in large quantities (parts per 100 of dry plant matter).  Macro nutrients are not more important than the other essential elements they are simply required in larger quantities. 

    1. Nitrogen (N)
    2. Phosphorous (P)
    3. Potassium (K)
    4. Calcium (Ca)
    5. Magnesium (Mg)
    6. Sulfur (S)

    Micronutrients

    Micronutrients also known as trace elements are elements that are required by plants in small quantities (parts per million of dry plant matter).  Micronutrients should not be mistaken as less important than their macro counterparts. 
    1. Boron (B)
    2. Chlorine (Cl)
    3. Copper (Cu)
    4. Iron (Fe)
    5. Manganese (Mn)
    6. Molybdenum (Mo)
    7. Nickel (Ni)
    8. Zinc (Zn)

    There are also other elements that although not essential to plants can be considered beneficial

    Beneficial Elements

    Beneficial Elements are elements that help optimize the growth and development of plants but they are not essential for growth.  When they are absent in the soil, plants can still live a normal life.  Here are some criteria that separate beneficial element from the essential ones:

    1. It can compensate for the toxic effects of other elements.

    2.  May replace mineral nutrient in some other less specific function such as the maintenance of osmotic pressure.

    3.  May be essential to some but not to all plants.
    Examples of beneficial elements are:

    Silicon (Si)
    Silicon increases the resistance of plants to pathogen and pests.  It also increases drought and heavy metal tolerance of plants.  Overall it improves the quality and yield of agricultural plants.

    Cobalt (Co)
    Cobalt is essential for the growth of Rhizobium bacteria for N fixation and thus beneficial for the plant.  Nitrogen fixation is the process by which the atmospheric molecular nitrogen (N2) is reduced to form ammonia (NH3).  This process is carried out by nitrogen-fixing bacteria which are found in the roots of most leguminous plants.  Ammonia is the form of nitrogen that is used by plants and other living systems in the synthesis of organic compounds.

    Lithium (Li)
    Affects transport of sugars from leaves to roots.  Production of food (carbohydrates and sugars) happens in the leaves during photosynthesis.  This food will be transported to the different parts of the plant such as the roots, fruits, new shoots, and stems.  Lithium enhances the transport of such food to the roots.

    Mature compost can provide all the essential and beneficial elements to your garden soil where your plants can access them. Growing certain plants and using them for mulch can also provide more of certain elements that may be needed for certain types of crop production and i'll be posting more on the details of this in the future.


    Fortunately  there is a very simple and effective means to ensuring an adequate supply of these elements to you garden ecosystem. Compost  :)


     Roles of Essential Elements in Plant Growth  - Macronutrients  

    NITROGEN
    • · Necessary for formation of amino acids, the building blocks of protein 
    • · Essential for plant cell division, vital for plant growth 
    • · Directly involved in photosynthesis 
    • · Necessary component of vitamins 
    • · Aids in production and use of carbohydrates 
    • · Affects energy reactions in the plant 
    PHOSPHORUS · 
    • Involved in photosynthesis, respiration, energy storage and transfer, cell division, and enlargement 
    • · Promotes early root formation and growth 
    • · Improves quality of fruits, vegetables, and grains 
    • · Vital to seed formation 
    • · Helps plants survive harsh winter conditions 
    • · Increases water-use efficiency 
    • · Hastens maturity 
    POTASSIUM 
    • · Carbohydrate metabolism and the break down and translocation of starches 
    • · Increases photosynthesis 
    • · Increases water-use efficiency 
    • · Essential to protein synthesis 
    • · Important in fruit formation 
    • · Activates enzymes and controls their reaction rates 
    • · Improves quality of seeds and fruit 
    • · Improves winter hardiness 
    • · Increases disease resistance 

    CALCIUM
    • · Utilized for Continuous cell division and formation 
    • · Involved in nitrogen metabolism 
    • · Reduces plant respiration 
    • · Aids translocation of photosynthesis from leaves to fruiting organs 
    • · Increases fruit set 
    • · Essential for nut development in peanuts 
    • · Stimulates microbial activity 

    MAGNESIUM
    •  · Key element of chlorophyll production 
    • · Improves utilization and mobility of phosphorus 
    • · Activator and component of many plant enzymes 
    • · Directly related to grass tetany 
    • · Increases iron utilization in plants 
    • · Influences earliness and uniformity of maturity 

    SULPHUR
    •  · Integral part of amino acids 
    • · Helps develop enzymes and vitamins 
    • · Promotes nodule formation on legumes 
    • · Aids in seed production 
    • · Necessary in chlorophyll formation (though it isn’t one of the constituents) 

    Roles of Essential Elements in Plant Growth - Micronutrients


    BORON
    • · Essential of germination of pollen grains and growth of pollen tubes 
    • · Essential for seed and cell wall formation 
    • · Promotes maturity 
    • · Necessary for sugar translocation 
    • · Affects nitrogen and carbohydrate
     
    CHLORINE
    •  · Not much information about its functions 
    • · Interferes with P uptake 
    • · Enhances maturity of small grains on some soils 

    COPPER 
    • · Catalyzes several plant processes 
    • · Major function in photosynthesis 
    • · Major function in reproductive stages 
    • · Indirect role in chlorophyll production 
    • · Increases sugar content 
    • · Intensifies colour 
    • · Improves flavour of fruits and vegetables 

    IRON 
    • · Promotes formation of chlorophyll 
    • · Acts as an oxygen carrier 
    • · Reactions involving cell division and growth 

    MANGANESE
    • · Functions as a part of certain enzyme systems 
    • · Aids in chlorophyll synthesis 
    • · Increases the availability of P and CA 

    MOLYBDENUM 
    • · Required to form the enzyme "nitrate reductas" which reduces nitrates to ammonium in plant 
    • · Aids in the formation of legume nodules 
    • · Needed to convert inorganic phosphates to organic forms in the plant 

    ZINC 
    • · Aids plant growth hormones and enzyme system 
    • · Necessary for chlorophyll production 
    • · Necessary for carbohydrate formation 
    • · Necessary for starch formation 
    • · Aids in seed formation

     NICKEL 
    • -Nickel is a co-factor or a way of helping to initiate the activity of particular enzyme that's important in the metabolism of nitrogen.




    As mentioned above, in addition to the 14 nutrients listed above, plants require carbon, hydrogen, and oxygen, which are extracted from air and water to make up the bulk of plant weight.


    Mineral Accumulators 


    The Zeus of  Mineral Accumulators - Comfrey - Symphytum uplandicum 

    Water moving through the soil via precipitation or irrigation will  inevitably wash mineral nutrients down the soil profile. Certain plants (often deep, tap rooted ones) will draw up these nutrients from the lower layers of the soil, and fix them into the plant tissue. As plant tissue is shed throughout the year, particularly,  in autumn and winter, the tissue is decomposed by the soil life and the nutrients captured from the sub soil  are incorporated back  into the upper layers of the soil and readily available to the plants.

    These plants are often refereed to in permaculture literature as dynamic accumulators and referred to in other literature as mineral accumulators. It is an area of botany with very little research to date.

    Our plant and seed orders are coming in for Autumn delivery. If you would like to purchase some plants this year to avoid disappointment order early as we have limited stock available.


     Balkan Ecology Project Bio-Nursery 

    Sunday, 1 September 2013

    Rain Water Harvesting on a 11.9 Hectare site " Dulga polyana"

    I am currently working as part of a design team for a 11.9 hectare farming project here in Bulgaria. The project will consist of an  Organic Cherry Orchard designed by  The Research Institute of Organic Agriculture (FiBL)  and a Forest Garden with Cherry featuring as the dominant Upper Canopy specie. My role is to design a Forest Garden area as well as looking into the rainwater harvesting potential of the site.

    View from the top of the watershed looking South
    The immediate challenge is to provide an irrigation solution that will meet the water needs for the whole site. Its a difficult site in that although flanked by two streams to the east and west and the river Chervishtitsa  to South , the land is like a huge wedge rising up above the flanking streams. Relying solely on water from the streams is not feasible or desirable, as water levels are very low in the dry months. Interception will inevitably disrupt the existing ecosystems and expensive pumping will be necessary to get the water uphill.

    There are over 5000 Cherry trees to be planted on this land and all will need irrigating, particularly in the early years. We estimated the water needs of the site to be 3300-3500m3 per year based on cultivating approx 7 ha of the 11.9 ha site.

    Annual Average Rainfall data for the region along with favorable topography indicates good potential for harvesting rainwater and storing it on the land in one or more reservoirs. My mission is to establish the practicalities of this.  

      
    A View from the South East / Boundaries marked with green line 
    My main focus during my first two day field trip was to get an impression of how water is interacting with the site. I walked the perimeter of the site marking on a GPS any signs of water erosion i.e rills and gullies and looked for patches of vegetation that stood out in the landscape such as dry or lush patches. I logged the elevation of key points throughout the site and tracked the source of perennial water flows i.e streams and rivers around the land. The aim was to build a picture of how the rainfall would move across the land , where it would settle, where it would drain and identify where best to intercept and store this water. 
    Once back to the computer I uploaded the GPS data to google earth and proceeded to sketch out my observations from the field onto the satellite image. I included erosion rills and gullies, elevation readings, slopes, current drainage channels etc. All this info on the map helps to build a vision of rainwater catchment potential of the site. With rainwater catchment the idea is to prevent water from draining off the site (causing erosion in this case) and divert it to an area where it can be stored. The ideal area to store the water should be the highest point on the land in order for the water reserve to be able to irrigate the largest percentage of crops via gravity. 


    The next step was to know what quantity of water is available to store. To work this out I needed to identify the watershed, i.e the area of surrounding land that contributes to a surface flow of water from rainfall events.

    Watershed above The Site
    Topographic maps are a great way of indicating the slope of the land. OpenStreetMap provides contour mapping for the world with 10m contour intervals, i.e each contour line is a difference of 10m elevation   from each other. This contour mapping can also overlay onto google earth. You can also adjust the appearance of the terrain on Google earth  if you would like the elevation to appear more pronounced in your views by modifying the 'Elevation Exaggeration value'. The default value is set to 1, but you can set it to any value from 1 to 3, including decimal points. Go to "Tools"  than to "Options" and you will see 'Elevation Exaggeration value' field under the Terrain section. This is great for getting a general overview of the terrain.   

    1.5000 Contour Map of the site. The narrow contour lines indicate that the land slopes sharply  into the flanking streams 


    Calculating Potential Rainwater Harvesting from Surface Runoff Annually

    The rainwater catchment area above the site is approx 59624m2. This figure only includes the area of land  that slopes towards the eastern and western streams and provides a conservative estimate of land that will contribute surface flow to the drainage channels that provide input to the reservoirs

    Taking a low estimate of the average annual rainfall for the region at 527mm. This indicates that the area can be expected to receive approx 527mm of rain per year
    By multiplying annual average rainfall (527mm) with the area of the watershed, (59624m2), we can estimate how much rain can be expected to fall on the watershed in an average year.

    59624m2 x 527mm = 31421848 L per annum

    Taking into account the absorption and evaporation rates of this water into the soil I have used a conservative Runoff Coefficient Value of 0.1 in order to obtain the expected amount of surface runoff that can be expected to drain from the watershed.  

    59624 x 527 x 0.1 = 3142184.8 L per annum

    3142184.8 L = 3142m3


    The next step is to establish a means to harness that water and store it on the landscape. 

       

    Interested in Ecological methods of growing food? Check out our Upcoming Courses and Events