Charlie Starr - Wine grape grower

Nutrient Management planning

Charlie Starr grew up around vineyards; today, together with his father and father-in-law, the family oversees around 100 acres of vines in Acampo, California. Since the 1960s, the families have been expanding vineyard acreage, with the oldest Zinfandel dating back to the 1960s and the youngest vines planted in 2005. The majority of their vines are Zinfandel, with about 10% Syrah. They currently sell their fruit to various wineries, including Sutter Home, Bogle, and Lange Twins.

In addition to the family vineyards, Charlie’s has been an Independent Pest Control Advisor for winegrape growers since 1998. In this position, he will consult on nutrient management practices, but it is really at his own vineyards that he manages all aspects of on-farm fertility. Charlie is also an active member of the Lodi Rules Research and Education Committee.

The nutrient management plan for Charlie’s family vineyards is based off of petiole samples, soil samples, and the inspection of the vines for visual symptoms of deficiencies.

“Nutrient management should never be reactionary, you need to have a plan,” Charlie says. “If you already see a deficiency, it may be too late to correct it that season.”

Creating a Nutrient Management Plan

Developing a nutrient management plan for grapevines requires testing vine nutrient status and understanding the nutrient requirements of the plant. Like most plants, grapevines take nutrients from the soil based on the stages of their development, and nutrient uptake curves have been developed to assist growers. By comparing the nutrient needs of the plant based on development stages with the results of the petiole samples from the vineyard, Charlie creates a nutrient management plan to provide the grapevines with the right amount of nutrients at the right time.

Generally, Charlie will take one petiole sample a season after bloom in mid-June. Viticulturists usually suggest taking the first petiole sample at bloom and others at critical stages of development through the growing season if needed, but Charlie has found that given his history with the fields 1 sample later in the season is adequate to keep a pulse on the nutrient status of the vines. Moreover, a single sample taken at bloom may not be able to predict potential deficiencies in his vines at veraison or beyond. If he detects any visual symptoms of deficiencies, he will take additional petiole samples during the season to determine how to correct for the deficiency.

Soil samples are taken in the winter about once every four years. Charlie has found that with the soil variability of his vineyards, these samples are not as accurate as petiole samples. Therefore, he prefers to invest in petiole samples instead of yearly soil samples. Both petiole samples and soils samples are compared from previous results in order to observe any long term trends in nutrient status.

With the petiole samples and the grapevine nutrient uptake curve, Charlie can determine the timing and rate of nutrient applications. Generally, application timings are:

May-June: Charlie limits nitrogen early in the season, since grapevine requirements are low. If needed, he will use multiple small applications of nitrogen during that time.

July-August: Around veraison, grapevine potassium requirements are high, at this time, Charlie will fertigate with liquid potash to meet those requirements.

October: Post harvest, Charlie will use a fertilizer mix that is heavy on potassium to help replace what was removed during harvest.

Nitrogen and potassium are the two nutrients that are added most frequently, but he may also add calcium, in the form of gypsum, boron, zinc, and phosphorus as needed.

Charlie will use yield information to determine how much potassium was removed at harvest to inform his potassium budget. In years when he has a heavy crop that is pulling large amounts of potassium, Charlie has used potassium foliar sprays pre-bunch closure or has banded dry potash on the vineyard plots with the above-ground drip irrigation system to meet potassium requirements.

Challenges with Nutrient Applications

Charlie’s vineyards are irrigated with either above ground or subsurface drip. These drip lines are used to fertigate the vines, and there are some challenges and trade-offs to these methods.

Fertigation allows for the targeted application of nutrients, increasing the efficiency of nutrient application. However, fertigation only applies nutrients to the roots below the drip emitters, and grapevines generally have root systems that move out into the soil underneath the vineyard rows. In years when the crop is large and the potassium requirement is high, Charlie has preferred to apply dry potash in a banded application. First, because dry fertilizer is less expensive than liquid based on a per unit cost; it is more economical to band large amounts of dry potash then to fertigate liquid potash. And second, the banded application increases the soil and rooting area that are exposed to the potash. Through this method, he has seen a faster uptake of the potassium. However, he will only use the banded application in the vineyards with above ground drip, as he can use the irrigation water to help the dry potash sink into the soils, as well as winter rains and tillage. This is not as effective with subsurface drip.

Fertigation is his preferred method of nutrient application unless large quantities of nutrients are needed. Fertigation is more efficient in its application of nutrients, allowing for less overall fertilizers to be used. It also reduces the amount of time and equipment needed for applications which keeps costs down with smaller applications. In 2012 and 2013, Charlie averaged $250 per acre on fertility.

Charlie has also experienced problems with his subsurface drip- mainly gophers- who will chew and puncture the drip tape. This will create leaks in the drip tape, which causes water and nutrient losses, but the leaks may also get plugged by root growth, which causes blockages in the tape. To combat this, Charlie and his family have put out owl boxes and traps for the gophers. Typically on a 17 acre block with underground drip about 30 gophers are eliminated throughout the year, but in the past as many as 300 have been trapped in a year.

Soil Management

Charlie uses a cover crop mix on a few of his vineyard fields. The cover crop is used to increase organic matter, increase nutrient availability, and to improve water holding capacity. Cover crops are not used on every vineyard.

Where he uses a cover crop, every other row is seeded and the cover crop is left to grow through to the next season. The other rows are disked 3 to 5 times depending on the year. The following year, the cover crop row will be switched.

On the fields without cover crops, he lets the native vegetation grow during the winter and early spring. Depending on the field, every row or every other row is disked 3 to 5 times a year starting in March.

Vineyard Irrigation

Charlie has neutron probes to monitor soil moisture levels, down to 5 feet deep. He checks these once a week to guide his irrigation events.

Irrigation events are scheduled using evapotranspiration calculations and irrigation formulas that allow for the replacement of certain percentages of vine water use depending on the stage of development. Charlie also directly observes the water status of the vines.

The Environment

With careful monitoring of irrigation events and with his nutrient management plan, Charlie is able to reduce the runoff and nutrient leeching from his vineyards. “I’m pretty sure we are doing a good job! We can use the neutron probes to see that the water isn’t moving beyond the rooting zone of the vines,” he says, “Fortunately, we are also on land that isn’t prone to runoff.” By matching his irrigation schedule to the evapotranspiration of the vines, and by using petiole samples and the nutrient uptake curves of the vines, Charlie is able to optimize his applications of nutrients and water to make sure that water and nutrients are staying on farm.

Advice for other growers

• “You have to be in the field, constantly!” says Charlie. Know your vines and vineyard so that you can use visual observation to detect any problems.

• Water and nutrients will move through soil types differently, so know your soils. Charlie indicates that his vineyards are on sandy soils and sandy-loam soils with clay layers. The different soil types will affect his irrigation and nutrient management decisions.

• Grapevines will take up nutrients differently based on rootstock and that will affect your nutrient management. Charlie’s oldest vines are planted on Dog Ridge, while the newer vines are on Freedom, O3916, and SO4. And he sees a difference in how fast the vines will take up potassium based on the rootstock.