Springtime Soil Fertilizer Applications for Orchards & Vineyards

BY KEN DAY 

Orchards and vineyards have two periods of root growth; one in the fall and one in the spring.  The “grand” period of root growth is in the fall just after harvest.  It continues into the fall until most of the leaves have fallen.  The second major “flush” of root growth occurs in the spring.  It begins just before bud break and continues until the fruit begins to enlarge later in the spring.  There is very little new root growth in the summer on bearing orchards and vineyards.  Neither do the roots grow during the winter while the trees and vines are dormant.

More than half of all nutrients are taken up during the fall root flush.  Hence it is recommended that half to two thirds of all soil applied fertilizers be applied post harvest in the fall.  The balance of all soil applied nutrients should be applied in the springtime during the springtime root flush.   

Foliar applications are generally more efficient for some nutrients like Calcium, Boron and Zinc.  But for the major nutrients nitrogen and potassium, the majority of these nutrients must be applied to the soil in order to fully meet the needs of the crop.  And, with highly efficient irrigation systems like drip and micro-sprinklers, it has become possible to also apply secondary nutrients like Calcium and even micro-nutrients like Zinc, as long as they are delivered in a protected or organically chelated form in order to bypass tie ups. 

What’s more, with the advent of our TRANSIT SOIL technology, all soil applied nutrients can be delivered more efficiently than ever before.  By improving the efficiency of applied nutrients, yield and quality and the bottom line can be improved as well.  A three year study on an almond orchard at the Huddleson Ranch in Hughson, California demonstrated this.  Although the same amount of nutrients were applied to the soil and foliage, yields and gross returns were increased three years in a row using a combination of Transit Soil and the FBSciences major and micro-nutrient products.

Grower returns for the FBSciences nutrient program increased by $656/acre in 2007, $560/acre in 2008 and by $209/acre in 2009 based on actual prices received by the grower.

Nitrogen

• The Nitrogen requirement of nut crops is much higher than for pome fruits or of vineyards.  But the principals are the same.  Sufficient Nitrogen is required in order to support full canopy development.  Generally a third to a half of the Nitrogen must be applied between bud break and the beginning of fruit enlargement. 
• Although slower release forms of Nitrogen can be applied in the fall, springtime Nitrogen should be mainly applied in the immediately available forms of nitrate or ammonium.  For some crops, even urea can convert too slowly in the springtime.  Organic Nitrogen converts very slowly in the spring.  It should only be applied in the fall.

Phosphorus

• Most orchard and vineyard crops do not respond to soil applied Phosphorus.  This is because the overall P requirement of these crops is low, and soil applied phosphorus is very inefficient due to tie ups. 
• Foliar applications of Phosphorus can contribute to earliness on crops where early harvest is desired.  In this case, foliar phosphorus may pay dividends.  But there is little research showing that foliar applied Phosphorus increases overall yields on permanent crops.

Potassium

• Most permanent crops require as much or more Potassium as they do Nitrogen.  Potassium is therefore the number one macronutrient for vineyards and for some orchard crops.  Because most soils have a huge capacity to fix (or bind up) Potassium, there is not an immediate yield response to soil applied Potassium in most cases.
• The general consensus among horticulturalists and viticulturalists regarding Potassium is to 1) apply bulk fertilizer Potassium mostly in the fall, 2) apply some liquid Potassium in the springtime if the soils are sandy, or if the irrigation system is highly efficient, and 3) apply foliar Potassium in the late spring and summer months to support fruit enlargement.

Calcium

• Because Calcium is not mobile within the plant, it must be supplied to the crop on a continual basis.  Supplying the crop with ample Calcium, therefore, requires an integrated approach. 
• This approach should include 1) applications of bulk Calcium amendments and fertilizers in the fall, 2) applications of highly available liquid Calcium in the spring, and 3) foliar applications during fruit development in the spring and summer months.

Zinc & The Micronutrients

• Zinc and other micronutrients (Fe, Mn, Cu) can be subject to severe tie ups when applied to the soil.  Since they are not mobile within the plant, most experts recommend frequent foliar applications of the micronutrients in the spring, early summer and fall months.  
• With the advent of highly efficient irrigation systems, it is now possible to see responses to certain forms of micronutrients through fertigation.  For Zinc and the metals, the best forms for fertigation are chelated with organic acids or with synthetic chelating agents in order to reduce the potential for tie-ups.  Our soil micronutrient range (Zicron-S, Photogreen-S and others) has been shown through numerous field trials to be more efficient than other soil applied micronutrients.