Maximum Yield Australia/New Zealand July/August 2020 | Page 48

“ PEven if your soil has high levels of phosphorus, compacted soil, herbicide damage, and root-feeding insects can decrease root growth and dramatically reduce a plant’s ability to uptake phosphorus.” Preventing and Treating Deficiencies Phosphorus content in Australian soil varies considerably, with the entire continent having naturally low phosphorus content due to weathering. The amount of phosphorus in the soil is influenced by many factors, including the material the soil was derived from, climatic conditions, amount of weathering and erosion, as well as crop removal and fertilisation. The best way to prevent a phosphorus deficiency is to test your soil at a reputable lab and amend it if necessary. Sources of phosphorus for your garden include manure, bone meal, rock phosphate, and phosphate fertilisers. Chicken manure is particularly high in phosphorus. Phosphorus availability is another important factor to consider. Just because phosphorus shows up on a soil test doesn’t mean it is available to your plants. Soil pH, temperature, moisture, and compaction will affect absorption rates. Ideal soil pH should be between 6.0-7.0 for maximum availability. Adding lime will raise the pH of your soil over time, if needed. Low soil temperature, excessive soil moisture, and soil compaction will decrease availability. Root growth can have a major impact on phosphorus uptake. Because phosphorus is very immobile in soil, it is important that the plant’s roots can grow through the soil to find the phosphorus it needs. It is important to consider all factors that affect root growth if you don’t want to end up with a deficiency. Even if your soil has high levels of phosphorus, compacted soil, herbicide damage, and root-feeding insects can decrease root growth and dramatically reduce a plant’s ability to uptake phosphorus. The soil environment in early spring, with its cold temperatures and water-logged soil, can cause roots to grow slowly. For this reason, many gardeners find that young seedlings can benefit from extra starter fertilisation when planting even if phosphorus levels in the soil are high. Increase Phosphorus Availability with Beneficial Microbes Microorganisms are key to making sure your plants get enough phosphorus. Soil that contains a healthy population of beneficial bacteria and fungi will promote strong root growth so there is more surface area for nutrient uptake. These microbes also break down unavailable forms of phosphorus into plant available forms. Phosphate solubilising bacteria (PSB) have been introduced to the agricultural community as phosphate biofertiliser and have been proven to improve nutrient uptake and reduce the use of synthetic fertilisers and pesticides. Three bacteria strains in particular have proven beneficial: Pantoea agglomerans, Microbacterium laevaniformans and Pseudomonas putida. Researchers at Colorado State University have shown that multiple strains of bacteria solubilise phosphorus more effectively than any one strain alone. You can apply PSB by inoculating seeds before planting, through fertilisation, and in hydroponic nutrient solutions. Compost and compost tea are additional ways to increase microbial communities in your soil, although if you want the PSB strains, you’ll need to buy a mycorrhizal inoculant with those specific strains included. Phosphorus is essential to healthy, vibrant plants, and maximum yields. It drives energy production and storage, which is the foundation of just about all the chemical reactions and processes throughout a plant’s lifetime. With these basic techniques, you can guarantee your garden will always have an available source of phosphorus and thrive. 48 Maximum Yield