Apple Rootstocks Economic Influence
Marketable yield is the driver of economic efficiency
Apple rootstocks play a very important role in your orchard, influencing apple tree growth rates, final size, precocity, fruit size, yield potential and nutritional responses. When deciding on a rootstock factoring in the scion vigour, soil vigour, climate vigour and rootstock vigour need to be reviewed to successfully achieve optimal growth and yield in your orchard.
Most growers are steering away from M.9 due to its susceptibility to fire blight and issues with sudden apple decline. Currently, growers are more inclined to try B.9, B.10 and various Geneva rootstocks such as G.41, G.935, G.65 and G.214. Some growers are experimenting with grafting, keeping the older established root system and rootstock with an interstem of the previous scion, and grafting the new scion selection on top. Although this practice is increasing in popularity, there aren’t many studies looking at the impact of economic returns regarding the comparison between pulling and replanting an orchard versus grafting onto an established orchard.
Looking further into the economic impact that rootstocks play in relation to bitter pit in ‘Honeycrisp’ apples, a preliminary study suggests that certain rootstocks can be accentuating losses in the orchard. This economic loss could be caused by the following:
1. Rootstock Selection
Less-than-optimal selection could result in less growth, height, and precocity. This then leads to a decrease in early marketable yields and slower growth to reach ideal state.
2. Rootstock Nutrient Uptake
Certain rootstocks uptake more nutrients than others, changing nutrient ratios and potentially increasing bitter pit.
3. Bitter Pit Yield
Although rootstocks may have a higher overall yield, they could also have a high bitter pit yield.
Planting rootstocks at their ideal density to maximize yield efficiency is important as well, but also in relation to the scion being selected. For example, Ambrosia grows very upright and planting at a higher density may be more ideal due to its growing habits in comparison to Gala, which has more of a horizontal growth pattern.
Depending on your orchard setup and management style, it may be beneficial to pair a low vigour cultivar with a vigorous rootstock to increase early year profitability. Keep in mind that a more vigorous rootstock may need more time to manage but would allow your scion to reach desired heights and ideal yields.
Overall, choosing your rootstock is an important decision that affects your orchard economics for the long term and is a decision that should not be taken lightly. When deciding on which rootstock will work for you, consider the following: scion growth, scion vigour, soil vigour, soil type, soil nutrient availability, rootstock nutrient uptake, rootstock vigour, orchard management and setup. Ideally, you should try to coordinate with your nursery suppliers, ordering trees well in advance so that you can get the desired rootstock that gives you and the nursery a performance edge in new orchards.
Remember, there is not one way to grow and establish a successful orchard. Do what works for you, your team, and your land, but remember that every decision is an economic one and that marketable yield is the driver of economic efficiency.