ANL has supplied commercial growing media, composts and mulches to a wide range of intensive horticultural sectors for decades. Specialist blends are available to specifically meet the needs of the growing environment, the grower and the stock turns set by the grower. A range of hydroponic mixes is also available and we recommend discussing available options with one of our qualified horticulturalists.
In-ground annual growers may wish to consider one our Compost and Humus products either as an annual or biannual amendment to boost soil productivity. Perennial growers may also consider these to reinvigorate longer term permanent plantings or to recondition soil prior to replant. Where weed suppression or moisture retention is paramount then our Mulch products may best suit. Specific blends of composts and mulches are also available.
ANL manufactures growing media under a number of products certifications including AS3733 (Potting Mix) and NASAA certified media for certified organic growers. Where specific media parameters are required to meet the needs of particular crops we recommend consulting our qualified horticulturalists for technical support and advice.
The performance of any growing media is a reflection of how well the relationship between air, water and nutrition meets the specific needs of the particular crop and growing environment. In addition, growers needs vary with regard to crop turns, shelf life, nutrient use efficiency and the cost and availability of water. Our advice is to consult one of our qualified horticulturists to determine the properties and mix formulation that most effectively meets the range of crop and grower needs.
As a general rule the more open a mix is, i.e., the higher the Air-filled porosity (AFP), then the faster the plant will grow assuming that adequate water and nutrition is provided. The faster it reaches a saleable size then the sooner it can be sold and another grown in its place. The down-side to this is that there must be available market demand to purchase the stock. For growers who have a reduced or intermittent market demand, then there is some advantage in reducing the AFP to slow the rate of growth. This also has the advantage of reducing the irrigation load since the mix will almost invariably have a great water-holding capacity (WHC) and also reduce fertiliser loss through leaching under irrigation.
Composts For Horticultural Production
One of the key productivity issues faced by many intensive horticultural production systems in-ground is particularly low soil organic matter (OM). The intensive nature of crop rotations gradually degrades OM as a consequence of regular and aggressive soil disturbance, significant irrigation and nutrient applications.
OM is a structural driver of soil water holding capacity (WHC) and nutrient use efficiency and of particular importance is the productivity benefits associated with the soil microflora. Plant availability of nutrients is not necessarily determined by the amount of nutrient present in the soil, but how the nutrients are released by the soil to the plants. Farm and soil management practices that include the management of microbiology will offer improvements in nutrient use efficiency and the recovery of N, P & other minerals and are typically associated with higher grain yields and protein levels.
Nutrient Use Efficiency
Where there is rapid uptake of nutrients around the root zone, the region close to the roots can become depleted and slow uptake and growth. This may be related to low moisture content however it can simply be a reduced nutrient concentration resulting from the speed of plant nutrient uptake during peak growing periods.
Plants can form a mutually beneficial or symbiotic relationship with microorganisms, particularly fungi, in which the fungi is able to access plant sugars from the plant root zone whilst it assists in releasing minerals and nutrients tied up in the soil, making them readily plant available.
Mycorrhizae: The Symbiotic Relationship between Fungi and Roots
A nutrient depletion zone can develop when there is rapid soil solution uptake, low nutrient concentration, low diffusion rate, or low soil moisture. These conditions are very common; therefore, most plants rely on fungi to facilitate the uptake of minerals from the soil. Mycorrhizae, known as root fungi, form symbiotic associations with plant roots. In these associations, the fungi are actually integrated into the physical structure of the root. The fungi colonize the living root tissue during active plant growth.
Through mycorrhization, the plant obtains phosphate and other minerals, such as zinc and copper, from the soil. The fungus obtains nutrients, such as sugars, from the plant root. Mycorrhizae help increase the surface area of the plant root system because hyphae, which are narrow, can spread beyond the nutrient depletion zone. Hyphae are long extensions of the fungus, which can grow into small soil pores that allow access to phosphorus otherwise unavailable to the plant. The beneficial effect on the plant is best observed in poor soils. The benefit to fungi is that they can obtain up to 20 percent of the total carbon accessed by plants. Mycorrhizae function as a physical barrier to pathogens. They also provides an induction of generalized host defence mechanisms, which sometimes involves the production of antibiotic compounds by the fungi. Fungi have also been found to have a protective role for plants rooted in soils with high metal concentrations, such as acidic and contaminated soils
Many perennial horticultural cropping systems utilise mulch as a weed suppressor and moisture retention agent. Depending upon the soil type and vigour, some growers prefer a blend of coarse mulch and fine compost which provides the soil conditioning of the compost in conjunction with the weed management and moisture retention benefits of the mulch.
As a rule, the type of mulch used depends on the health and quality of the soil. Where soils are depleted with low O.M. and poor nutrient retention then it is common to use a composted mulch such as Vine Mulch as has been applied to the apple orchard below. Where soil health or improvement in O.M. is the primary objective then on occasions compost is used as a mulch such as with the Macadamias below, to drive improvement in soil texture and structure rather than weed suppression.
Where there is no concerns regarding nutrition such as in a container production environment then uncomposted mulches are commonplace. The key objective in most of these applications is weed suppression.
Mulches vary in their effective life span. Being organic they will naturally decompose over time and as a general rule, the coarser the grade the longer it lasts. Much of the decomposition is done by saprophytic wood fungi which may strongly populate woody mulches in particular. If the environment is right and the mulch is applied at a relatively high application rate of 100mm then the fungi may grow excessively and develop an extensive network of hyphae throughout the mulch. Where the hyphal growth is excessive, the mulch can become tightly matted and hydrophobic (water repellent).
To counter this, likely tine the mulch to break the fungal hyphae and allow air and water to penetrate. In addition, some seaweed based products may contain chemicals which effectively act as natural surfactants or wetting agents. Watering with seaweed extract fertilisers may help reduce the water repellence while adding liquid fertiliser to the soil.