HFIT

Herbicide, Fertilizer, Irrigation, Tillage

Herbicide

Overview

There are many pros and cons to using herbicides to help your shelterbelt grow. Before planting, herbicides can be applied to the soil to control many annual grasses and broad-leaved weeds. Be cautious though! Excessive levels of normally helpful herbicides can harm shelterbelts. Herbicides can also be dangerous from second-hand sources (spray drift). 

There are many pros and cons to using herbicides to help your shelterbelt grow. 

Herbicides can be bought at agricultural crop protection suppliers and can be applied in late fall or early spring. Before planting your seedlings, a herbicide can be applied to the soil to control many annual grasses and broad-leaved weeds from growing. A herbicide for this purpose can and should be trifluralin (Treflan or Rival). Trifluralin inhibits proper cell division and formation and mainly affects root production . Other weeds that cannot be controlled by trifluralin, such as weeds in the mustard family, can be controlled by other herbicides after planting. Another herbicide popularly used to control Canada thistle is Clopyralid. These other herbicides include clopyralid, dichlobenil, linuron, simazine, fluazifop-p-butyl, sethoxydim, amitrole, glyphosate and paraquat. 

On the other hand, some herbicides can leave harmful residues on shelterbelts (especially young ones). Excess levels of normally helpful herbicides can also harm shelterbelts. 

Herbicides can also be dangerous from second-hand sources; this meaning that spray drift from nearby fields can damage shelterbelts. Some shelterbelt species are more susceptible than others. The most effective way to reduce spray drift potential is to use spray with larger droplets, which can be varied through nozzle selection and spray pressure. This way, droplets less than 150 um in diameter are reduced. This is important and useful since smaller droplets travel further by wind.

Some of the most threatening herbicides to most trees include phenoxys, dicamba, bromoxynil and picloram. One product specifically dangerous is Estaprop. These herbicides can come in different re-mixed formulas as well. Take extra caution when using these herbicides near shelterbelts as they can be damaged if the herbicide is improperly or overly used. 

Herbicide application equipment

Overview

Equipment used to apply herbicides mainly includes field sprayers attached to tractors, spray guns, and spray booms. It is useful to spot-spray herbicide only onto the areas that have proven to need it. Granular herbicides can also be applied to the area by hand-operated applicators. 

Equipment used to apply herbicides mainly includes mainly field sprayers attached to tractors, spray guns, and spray booms. Spray booms and spray guns are used in the same fashion: simply spraying the herbicide around the shelterbelt while following package instructions. Spray guns and booms are useful for smaller scale herbicide applications, and field sprayers are used for larger operations such as entire fields, so field sprayers may not successfully apply herbicide to all spots around a shelterbelt. 

Spray booms and guns are useful for shelterbelt areas. Spray guns often consist of a spray nozzle and backpack, which make it easy for herbicide application to be a simple, one man job. Spray booms are a larger version of the same type of tool. They are often pulled by tractor and consist of a tank of herbicide and spraying materials used to spray the herbicide over larger areas. When applying herbicide, it is recommended to wear face protection as to not ingest any herbicide and to protect one’s eyes (see image 1).

Image 1. A spray gun with nozzle and backpack being used to apply herbicide.
Source: https://cdn.the-scientist.com/assets/articleNo/30308/iImg/1481/605af452-974f-4063-8f1e-2869d2007bac-roundup-man-full.jpg

It is useful to spot-spray herbicide only onto the areas that have proven to need it. This is also beneficial since it reduces the risk of over-application. 

Granular herbicides can also be applied to the area by hand-operated applicators. There is risk of human error here to over- or under-apply different areas, so care must be taken to apply a uniform and correct amount of herbicide in this fashion. 

Fertilizer

Overview

Fertilizers have some pros and cons as well. Many shelterbelt enthusiasts believe the use of chemical fertilizers has far more cons than pros because it is often misused. Some believe the use of chemical fertilizers is not recommended because incorrect use can be very common. Nutrient additions or bone meal can sometimes be more appropriate. In general, fertilizers are acceptable as long as proper application of proper amounts are consistently maintained. A rule of thumb is that fertilizer should only be applied where absolutely necessary. 

Image 2. Fertilizer (white granules) in soil.
Source: https://www.biovoicenews.com/wp-content/uploads/2016/11/Fertilizers.jpg

Some believe the use of chemical fertilizers is not recommended for new seedlings because incorrect use can be very common. Over-application is especially common and can kill the new trees. Nutrient additions or bone meal can be more appropriate alternatives if soil amendment is wanted. These amendments can promote faster root development and subsequent above-ground tree growth. These can be bought at stores such as Home Depot or Canadian Tire. Simply follow package instructions. Fertilizers, if incorrectly used, can also promote suckering of the trees. Tree suckers are additional growths from the main tree stem, and are not normally wanted. The environment is more controlled when suckers are not present. 

Others believe that fertilizers are acceptable during this stage as long as proper application of proper amounts are consistently maintained. These are applied of course where soil nutrient levels are low. Fertilizers this way can aid in establishment of the seedling.

An overall rule of thumb is that fertilizer should only be applied where absolutely necessary. Fertilizers should not be routinely applied to healthy areas or fields that receive constant and/or proper management already. 

Irrigation

Drip irrigation overview

Drip irrigation is a very popular agricultural method of supplying water to crops or other plants, such as a shelterbelt. A drip irrigation system consists of two main parts which are the “head” and the subsequent distribution pathway. Drip irrigation is suitable for many environments and is an efficient way to water plants since there is very little seepage and evaporation. Drip irrigation can be used throughout the shelterbelt lifetime. 

A drip irrigation system consists of two main parts which are the head and the distribution pathway. 

  • The head includes the water source, pump, pressure regulator, etc.
  • The distribution pathway includes the main water distribution line and smaller lateral dripper lines which are situated near the base of the plant.
Figure 1. An example of a drip irrigation system.
Source: https://www.agr.gc.ca/resources/prod/img/agrofor/planning_establish_fig11_eng.jpg

Drip irrigation consists of laying down a water emitter such as a small PVC or polyethylene pipe directly near the plant which supplies water to the adjacent area in small drips. By this method there is very little seepage and evaporation; therefore there is little water loss in drip irrigation. Avoidance of water loss is tremendously beneficial.

Drip irrigation can be used from the moment a seedling is planted until the end of its life. Drip irrigation has been seen to be especially helpful in drier areas to establish coniferous species such as the Colorado spruce.

Surface/Flood Irrigation

An older method of irrigation is surface or flood irrigation. This method consists of flowing water down trenches that run adjacent to shelterbelts, providing water by gravity. The trenches can be dug with machinery or tools such as shovels, and water can be transported to these trenches by means such as by handheld water buckets, pipes, or more (see image 3).

Image 3. An example of surface irrigation (specifically, furrow irrigation) with trenches and pipes. This same irrigation method that this crop is receiving can be applied to a shelterbelt area.
Source: https://www.mississippi-crops.com/wp-content/uploads/2015/12/0004.jpg

The water is directly poured onto the trench area on the ground surface. Because of the relatively uncontrolled water application technique, surface irrigation is naturally less efficient than drip irrigation due to water waste and loss from runoff. Therefore, surface irrigation is not normally as popular as drip irrigation in Canada. However, it is a cheaper and less technological way to irrigate a shelterbelt, which can be convenient for some shelterbelt planters. There are also ways to prevent surface runoff, such as levelling the ground area where the shelterbelt will be, before planting. One can also collect the runoff water and reuse it.

Tanker and Sprinkler Irrigation

Tanker irrigation is a type of irrigation system including either an underground or aboveground tank.

  • An underground system includes an underground water tank located nearby the shelterbelt roots. Attached to the tanker is a pipe leading up to the ground surface where water is fed into the system by hose or other means. The water travels through the pipe to the tanker where it is released around the plant roots. A slow release system can be installed to control water release to the shelterbelt. This controlled watering results in proper, healthy plant growth and increased longevity due to the avoidance of under- or over-saturation.
  • An aboveground system includes an aboveground water tank and trailer normally hauled by tractor. Water application can be either manual or automatic. To be done manually, a tube can attach to the water tank leading to a handheld hose or sprinkler head that a person can hold and spray the area with. To be done automatically, a motor and pump could be attached to the tank in to automatically apply water on the area through sprinkler heads on the back end of the water tank (see image 4).
  • A sprinkler system can be installed around the shelterbelt to provide controlled watering to the area as well.
Image 4. An example of an aboveground tanker irrigation system with automatic sprinkler heads on the back end of the water tank.
Source: https://www.abiattachments.com/wp-content/uploads/2019/05/500-water-trailer-image-2.jpg

Tillage

Overview

Tillage includes multiple types of land preparation for agricultural areas in order to successfully grow crops. Tillage controls the amount of crop residue removed or left for the next crop. Since shelterbelts are not crops, the areas mainly take advantage of tilling practices for weed control. There is human-powered/hand tillage, animal-powered tillage, and mechanical/industrial-scale tillage (the most popular of the three). There are different rates of tillage, including “conservation”, “intensive” and “zone” tillage.

As a physical alteration, tillage has many implications to the soil. Tillage can also have costs implemented from energy, fuel use, machinery, labour, etc. However, tillage has valuable benefits such as the promotion of biological activity and reduced soil degradation (regarding conservation tillage).  

Cultivated land is tilled, meaning dug into, stirred and overturned, normally in order to control the amount of crop residue removed or left for the next cropping season. This is done to create a suitable seedbed, eliminate weeds and therefore competition, and improve soil conditions and productivity. These benefits towards crops can also be seen in shelterbelt areas that are tilled.

Image 5. A first-person view from a tractor of the process of tilling soil.
Source: Colin Laroque

There is human-powered or hand tillage, but this type of tillage continues to lose popularity in industrial agriculture. Although this, hand tillage could be very useful for smaller-scale shelterbelt projects. Methods of human-powered tillage methods using hand tools include shoveling, picking, hoeing and raking. 

Animal-powered tillage was also popular in the past and includes rototilling and plowing. This method could also be used for small-scale shelterbelt projects, although not terribly popular. 

  • Rototillers and plows are both types of machinery that use blades to cut into and churn (i.e., cultivate) soil before planting a shelterbelt.

Mechanical/industrial-scale tillage can come in many shapes and forms, including and mainly rototilling and plowing as well. These include different degrees of tillage as well, meaning how much of the crop (or shelterbelt) residue is left in the soil for the following year. There is conservation tillage (at least 30% of residue is left in place), reduced tillage (15-30% of residue is left in place), intensive tillage (less than 15% of residue is left in place), and zone tillage (modified, narrow strips of land are tilled, leaving soil between rows untilled). Mechanical tillage is driven by machinery such as tractors that pull tillage equipment behind them to cultivate the landscape. 

Energy requirements can be high for intensive tillage; this rate of tillage may not be suitable for everyone and all projects.

Of course, since shelterbelts are not crops, shelterbelt areas mainly take advantage of tilling practices for weed control. This can be done before the seedlings are planted, and during and after the site preparation stage. The area can be tilled the year before the seedlings are planted. By tilling the land, weed competition is limited or eradicated, and the nutrients present in the soil are thereby available solely to the new seedlings. This is important, since seedlings are very sensitive to external influences such as competition.

Tillage has many implications to the soil. 

  • Leaving the soil surface bare after tillage can subsequently be very susceptible to erosion. Be careful of this especially if your soil area is already endangered by erosion.
  • These implications can be different with different tillage operations. For example, preplant tillage disturbs the entire soil surface by other operations such as cultivation between rows only alters said soil between rows. 

Conservation tillage can lessen the soil degradation that other tillage practices may result in. 

Tillage can have costs implemented from fuel use, machinery, and labour.

Tillage tends to reduce SOM since it incorporates air in the soil. This promotes biological activity. The carbon in the organic matter is food for the microorganisms which leads to a loss of SOM as CO2. Of course OM is important for soil health, but maintaining good aggregate structure with this method is also important. 

Certain herbicides cannot be coupled with conservation tillage, but instead with other forms of tillage that protrude into the soil, due to the need for physical incorporation. 

Image 6. Tilled land surrounding a shelterbelt.
Source: Colin Laroque

Additional Information:

References: