In an effort to manage climate variability, whilst increasing production, more and more attention is being to what’s under our feet. Understanding soil biology is embracing a dynamic environment that will ultimately provide us with increased performance that is sustainable.
This article is about considering the role machinery can play in overcoming soil compaction and improving soil health.
1. Soil Compaction
(a) Remedial action
2. Conservation Agriculture
(a) Minimum tillage
(b) Minimum tillage machinery
1. Soil Compaction
Soil compaction is an increase of density as a result of repeated passes of heavy machinery over the field. This can be compounded if the machinery is used when the soil is loaded water. The side effects are a negative impact on soil porosity impacting the movement of air and water as well as microbial activity. The movement of roots is also impeded due to increased mechanical resistance due to increased soil density.
Interestingly research suggests that microbes play a crucial role in this ecosystem, regulating over 80% of all chemical reactions taking place in soil. These reactions break down complex chemical compounds, producing essential nutrients for plants and soil-dwelling animals. [ 1 ]
As a result of soil compaction crop yield is severely due to the side effects mentioned.
In modern farming it’s not possible to eliminate compaction altogether. However, conservation tillage practices can be utilised to minimise damage, improve soil porosity and increase microbial activity.
1 (a). Remedial action is often necessary
If it is established that compaction is an issue, then consideration needs to be given to remedial action. The most effective method is to assist natures work by subsoiling. The intention of sub soiling is to create vertical cracks and shatter the soil. This mechanically reintroduces porosity achieving better air movement, water penetration and microbial activity. It also allows a plants roots to grow and travel more freely thereby accessing moisture and nutrients.
Timing is everything – if the soil is too wet it will more like plasticine and won’t shatter. If there is a hard pan, then setting the machine depth is critical to get below the pan to break it up.
2. The role of minimum tillage in conjunction with Conservation Agriculture (CA)
Conservation Agriculture has three pillars
Pillar 1 – Minimum mechanical soil disturbance: Minimum soil disturbance refers to low disturbance no-tillage and direct seeding. The disturbed area must be less than 15 cm wide or less than 25% of the cropped area (whichever is lower). There should be no periodic tillage that disturbs a greater area than the aforementioned limits. Strip tillage is allowed if the disturbed area is less than the set limits.
Pillar 2- Permanent soil organic cover: Three categories are distinguished: 30-60%, >60-90% and >90% ground cover, measured immediately after the direct seeding operation. Area with less than 30% cover is not considered as CA.
Pillar 3 – Species diversification: Rotation/association should involve at least 3 different crops. However, repetitive wheat, maize, or rice cropping is not an exclusion factor for the purpose of this data collection, but rotation/association is recorded where practiced. [ 2 ]
In preparing the ground for a crop it is acknowledge cultivation physically disrupts the soil, exposing the soil surface to erosive forces, and facilitating the oxidation of organic materials. Cultivation can include reduced infiltration, erosion, crusting, and reduced plant growth.[3 ]
2 (a). Minimum tillage – minimum mechanical soil disturbance
In relation to minimum tillage which reduces mechanical soil disturbance, there are some key objectives.
Minimise damage to soil structure, avoid the loss of soil, and reduce the evapo-transpiration of soil water. Conservation tillage leaves 30 % or more of the soil surface covered with crop residue. Minimum tillage simply describes the aim of conservation tillage. It involves three or less tillage passes (including seeding).
What are the benefits of minimum till systems?
Stubble retained as ground cover steadily adds to the reservoir of soil organic matter. This in-turn will lead to improved soil structure and increased aggregate stability. Ground cover also decreases erosion with less exposure of the soil to erosive forces. Another significant benefit to minimum tillage systems are the savings on machinery hours and fuel. The economic benefit of minimum tillage will vary from farm to farm but savings on inputs are in the order of 15 % to 30 % Yields will not alter much for the first few years but histories show gradual yield increase from the fourth or fifth year and continuing up to 30 % (Tullberg et al. 2003). If combined with controlled traffic farming this can further increase input savings and yields. Various experiments across Australia are showing the potential for yield increase with the intelligent use of minimum tillage.
As an example of how soil type affects the management of soil, red loamy soils, unlike sandy soils, do not respond to cultivation. Even a zero-disturbance triple disc drill produced yields equal or better than cultivation, especially when adequate nitrogen was applied. With no benefit evident from cultivation of these soils, the system of lowest cost and superior erosion prevention is the best option (Anderson 2000).
Are there any limitations to minimum tillage systems?
Limitations of a minimum tillage system are weed management, herbicide resistance, machinery suitability, and occasional outbreaks of pests.
The pioneers and other long-term practitioners of minimum tillage cropping (particularly no-till systems) have developed strategic and effective herbicide management and application. This includes timely control of any summer weeds and a grass control product in a mix with a knockdown product in front of the seeder, then early application of any in-crop weed control if required. [ 4 ]
2 (b). Minimum tillage machinery
There are a number of machines capable of achieving cultivation to a shallow depth whilst incorporating crop residue. With a working depth of up to 100mm and a ground speed of around 10 km/hr these machines are a highly effective option for crop preparation. With the aim of improving crop yields and reducing the cost of crop establishment the use of minimum tillage machinery is a worthwhile consideration.
More information can be found at:
[ 1 ] https://microbiologysociety.org/blog/under-pressure-how-do-microbes-grow-in-compacted-soil.html
[ 2 ] http://www.fao.org/conservation-agriculture/overview/principles-of-ca/en/
[ 3 ] http://vro.agriculture.vic.gov.au/dpi/vro/vrosite.nsf/pages/soilhealth_cultivation
[ 4 ] http://vro.agriculture.vic.gov.au/dpi/vro/vrosite.nsf/pages/soilhealth_cultivation