Nutrient Seed Dressings

Nutrient seed dressings should be a high priority for broadacre farmers as they are the most efficient and cost effective method of supplying essential trace elements like zinc & manganese to the crop. For less than $1 an acre, growers can treat their seed and expect a minimum 5% increase in grain yields in most seasons where an average crop is harvested. A recent study found that Australian wheat had the lowest zinc levels of all the major wheat producing countries and this has significant implications for both animal and human health. It also means that the seed you are planting is already low in zinc and this has potential to limit early development and yields.

Zinc seed dressings are the most commonly used due to the universal nature of zinc deficiency across most soil types in Australia and the importance of zinc for early crop development. Zinc is required for the synthesis of the growth hormone auxin which promotes root and top development. Seed dressings are also a very efficient way to supply available zinc at this early stage as zinc is immobile in the soil and availability of zinc applied with base or planting fertilizers is often limited due to precipitation in alkaline or high pH soil conditions.

Other nutrients that can aid germination and early development are manganese, copper (at low levels as it can be toxic), molybdenum & phosphorous. In legume and canola crops boron can also enhance early growth & establishment. One advantage is that many of these formulations are compatible with seed pickles (eg. bunticides, smuticides) so a separate dressing operation is usually not required. Some are also possibly compatible with legume innoculants however those containing copper may be toxic to rhizobium so care needs to be taken.

Aside from yield benefits, seed dressings usually have quite positive effects on root development and germination. Farmers often report that treated seed will emerge 2-5 days before untreated, while the image below shows the significant increase in early root development due to nutrient seed treatment (left). Obviously increased root growth is a major advantage for a plant in terms of water and nutrient availability and this tends to reduce plant stress and enhance crop tolerance to disease & pest attack. The independent scientific trials we have commissioned in NSW, VIC, SA & WA have shown grain yield increases of up 18%.

A question we are often asked is, “Do I still need to apply a zinc foliar spray if I use a seed dressing?”. There is no single answer to this question and much will depend on your soil type and yield potential. Generally we find that there is still a yield benefit with foliar sprays on deficient soils like those in SA and the Victorian Mallee and seed quality (eg. protein levels) is also enhanced. In many areas there will be a need to apply a foliar spray of manganese (eg. SA) or copper (WA) anyway as these nutrients cannot be fully supplied as a seed dressing so most growers will also top up with zinc as well. Leaf tests at 3-5 leaf stage should give you a good idea of zinc status and if extra foliar zinc is required.

SJB has several seed dressing products to suit any crop or soil type.

 

Almond Post-harvest Nutrition

Soil Nutrients – Nitrogen and potassium are the biggest nutrient requirements for almond crops and generally it is recommended that about 1/4 of the total N & K requirements are applied post-harvest, however this should be assessed based on the current season’s crop load. Almonds use these nutrients to supply energy and sugars for flower and early shoot development for the next season. It is critical to ensure soil moisture levels are optimal when N & K are applied (or any soil fertilizer for that matter) otherwise fertilizer efficiency/uptake will be low and there is also potential for root damage in dry soils due to the high salt index.

Phosphorous is essential for reproduction, energy production (eg. ATP) and cell division. While almond trees do not have a large P requirement (30 kg P/ha for maintenance in bearing trees) it is critical during the bud-burst to fruit set period so it needs to be available as soon as roots become active in late winter. If soils are low in sulphur then applying Single Super post-harvest will be beneficial, while more available forms (eg. MAP/DAP/MKP/APP) should all be applied pre-flowering & during early fruit development.

Some growers may also be applying phosphonate (eg. PHOSIC 600) post-harvest to address any phytophthora concerns. While some companies may claim that the phosphorous (eg. phosphite) in their phos acid products is available to the trees as a nutrient source, this is simply not true at least in the short to medium term. Phosphite that remains in the soil will over time (eg. 6-12 months) be converted to the plant available phosphate form, however it should not be relied upon as a P nutrient source for the coming season. Growers should also be aware that the phosphite MRL for almonds going into Europe has been lowered to 2ppm as of Dec 31 2015, so you may need to find an alternative product if your nuts are going to this market.

Post-harvest is also a good time to apply calcium if exchangeable levels are low in the soil or pH needs adjusting. While calcium may be considered a less important nutrient by many, my experience in the field indicates that there is a direct relationship between tissue calcium levels and kernel yield. Calcium is also an important nutrient for reproduction and pollen tube development, so it is essential that tree calcium levels are optimal before they go into dormancy (pre-flowering application of calcium nitrate will also be beneficial).

Zinc and boron are both essential trace elements for almond production and are required for reproduction, shoot development and fruit filling. In seasons where you have average to good yields with good shoot development, demand for boron and zinc will be high so levels in the trees may be depleted and therefore post-harvest application is even more critical in this situation. Boron is quite mobile in lighter soils & so has good availability but can also be lost through leaching if over applied. If soil boron levels are <0.5 mg/kg then look at applying 1-2 kg B/ha. If boron hull levels are also <80 mg/kg consider the higher rate. Unlike boron, zinc is basically immobile in the soil and therefore soil application is less efficient, particularly if soil pH is alkaline. Best zinc availability will be seen on sandy acid soil types where exchangeable zinc is <2 mg/kg. Young trees will usually benefit the most from regular soil zinc application. Look at applying 1-2 kg Zn/ha.

Foliar Nutrients – Post-harvest foliar sprays are essentially aimed at ‘bud building’ for the coming season and nitrogen, zinc and boron are the main nutrients of interest in this regard. Lo bi urea is used in many crops to aid bud development/health and the Almond Board recommends applying a 1% solution (eg. 1 kg urea/100L) in late April and early May. Numerous studies in almonds indicate a consistent benefit from post-harvest foliar boron sprays in terms of improved fruit set and nut retention in the following season (250-500 g B/1000L). Given the high boron requirement for almond production, I would still recommend both soil and foliar application, particularly on low boron soils. Like boron, foliar zinc has also shown to be beneficial for bud development and fruit set, mainly due to its role in auxin production (an essential plant growth hormone).

While there are various factors that determine potential fruit set, nutrition is one that (unlike the weather) can be controlled & manipulated by growers to ensure their trees have the best chance of setting an optimal crop.

Defoliation – There has been some discussion on the best option for defoliation of trees prior to dormancy. Traditionally, high or phytotoxic rates of zinc sulphate have been used and it was thought this would provide some zinc to enhance bud development for the coming season. The other alternative is to use high buiret urea (eg. 70 kg/1000L) to defoliate. In terms of foliar absorption, nitrogen is absorbed much faster (hours) than zinc (2-5 days) which only has limited plant mobility. Also the condition or health of leaves has a major effect on foliar uptake and at this time of the season the condition of leaves is usually not that suitable for foliar uptake anyhow. So the reality is that zinc sulphate will probably not supply any available zinc for the coming season, whereas urea is more likely to supply some nitrogen for bud development.

SJB Soil Applied Nutrients

Boron PLEX

Calcium + Boron PLEX

Zinc PLEX

SJB Foliar Applied Nutrients for Bud-building

LIGNO-BORON

LIG-TRACE

LIG-ZINC

LIG-ZINC + BORON

Systemic Fungicide for Phytophthora Control

PHOSIC 600 (can be applied to the soil or as a foliar spray)