The spring of 2019 has been challenging for almond growers with greater than average rainfall and cooler than normal soil temperatures. Access to apply timely fungicides has been poor due to excess soil moisture. Nitrogen and potassium applications following leaf-out were pushed back up to two weeks in some cases. This has put many growers in a position where they are scrambling and adjusting to get the needed quantity of nitrogen on by the typical June 1st cutoff that many are adhering to currently. Though it doesn’t require a hard cutoff like nitrogen, potassium is also in very high demand at this time and compatibility of some potassium sources can exacerbate this logistical compression.
In years like this, it is imperative to maintain good agronomic practices and not lose sight of nutrient dynamics. There may be intent to limit the number of applications using larger volumes of nitrogen fertilizer, particularly UAN-32, to catch up on amount of N needed to produce the crop. While this practice may work in some high CEC (Cation Exchange Capacity) soils, it can be wasteful, detrimental to groundwater, and limiting to overall production in other cases. Trees have a limited ability to take up and utilize nutrients. This is similar to the human diet where gorging followed by fasting may provide the necessary calories on average but will produce an internal imbalance on both ends of the swing that will impede proper development. Trees require and demand specific nutrients for specific functions at specific times. Providing readily available nutrition during critical demand periods will facilitate nitrogen uptake leading to optimum tree health and ultimately yield. Nitrate-nitrogen fits well in a sound fertility program. Split applications of nitrate-N during peak demand can ensure trees have readily available nitrogen in the soil solution when they need it. Splitting applications of nitrogen not only extends the availability of nitrogen to the tree but also provides the amount of nitrogen the tree can effectively take up and limits the amount of nitrogen that can leach past the active root zone. The increase in plant available nitrogen in the anionic nitrate form can also increase the uptake of positively charged cations such as calcium, potassium, and magnesium into the plant roots.
Improved root growth in citrus trees fertilized with YaraLiva CALCINIT
Quaggio et al., unpublished data.
Potassium demand is similar to nitrogen demand in almonds because it is required in greater proportions early in the growing season. This period of nitrogen and potassium demand coincide with the major root growth period for the year. In the same way nitrate-nitrogen provides readily available nitrogen in the soil-solution, the nitrate form of potassium can supply immediately available potash for tree roots to pick up. Adequate supplies of potassium have been linked to increasing fruiting spurs, facilitating carbohydrate metabolism, transporting sugars, promoting root growth, and regulating leaf stomata. One of the most important factors at this stage of development is promoting root growth. Superior root growth will pay dividends because it enhances the tree’s ability to then mine more nutrients and moisture from the soil, better protect itself from disease, and more effectively mitigate abiotic stresses. Calcium also plays a significant role in the process of the tree defending itself from disease and abiotic stresses, but it must be taken up by the actively growing roots that we are supporting. It is imperative to have soluble calcium available during this period of vigorous root growth as the calcium ion is taken up just above the active root tip and when root tip activity is limited so is calcium uptake.
At this point, the picture of how all these interactions are intertwined should be coming into focus. Supplying each required nutrient at the appropriate time, in the appropriate amount, in the appropriate form, and delivered to the appropriate location allows those applied nutrients to pay dividends and increase your return on investment. At this stage of development, the most critical soil-applied nutrients are readily available forms of nitrogen, calcium, and potassium Products such as YaraLiva CN-9, potassium nitrate or YaraTera 5-0-7 are ideal to supply your trees with these critical nutrients.
We are now in the full swing of irrigation season and it is important to note that effectively managing irrigation and fertigation events are the key components to a successful nutrient management program. There is no easier way to compromise a well-developed nutrition program than to mismanage the water that is expected to deliver those nutrients to the tree. Feed your almond trees responsibly!
Crop Manager, Tree Nut
With 40 acres of fertigated and established almonds, and 40 acres of irrigated and established walnuts, the Yara Incubator Farm in Modesto, California is a center for research, solution trials and knowledge sharing.