Tuesday, June 7, 2016

Vineyard Health: Being a Dietitian to Plants and Soil

So if you're new to my blog, you may know know that I practiced as a clinical and long term care dietitian for many years before transitioning full time to our family farm. I still use these skills day in and day out as the science of nutrition is still the same,  I'm just applying it to a different biological system. If you haven't found me yet on Facebook, I'm known as The Foodie Farmer. I post almost daily what I'm doing on the farm and use Facebook as my mini-blog or "view from the office" and general stuff of interest in ag and random topics.

Today I walked up and down and up and down about 20+ acres of grapes in our vineyard. This is a critical time of year for grapes as the plants are in bloom. The blossoms need to be pollinated in order for fruit to developed. Cultivated grapes are hermaphroditic, meaning they have both the male and the female parts needed to self-pollinate. Pollinators like bees are not required for grapes to be pollinated. Bees seldom visit grape blossoms, probably because they are near microscopic, not very floral, not very attractive, and offer little nectar for the bee. There are much bigger blossoms around that would be less work for the bee that's for sure.

Chardonnay blooms

Chardonnay blooms

Plant and soil health tools of the trade
 My goal for today is the pull soil samples to check for nematodes and petiole samples to check the nutrient uptake of the plant at this stage of growth. I need a bucket for collecting soil cores, a soil sampler, and a paper bag for collecting petioles.

Pulling a soil core
 I need about a pint of soil per sample and I've divided my vineyard into blocks basically by variety so I know what I need to do where when the test results come back. I pull more soil than I need, mix it together in a bucket and pour about a pint of soil into a ziplock bag.

4-10" of a soil core is recommended for nematode sampling in a vineyard.
Soil cores taken at random intervals from the root zone of the grapevine.
Rapeseed cover crop to remediate for nematodes

I want to know what level of nematode pressure there is in my vineyard and what types of nematodes are present at what levels. Not all nematodes are bad, some are beneficial. So my approach to remediation has been to plant a cover crop of rapeseed which is in the brassica family. When it is rototilled into the soil and decomposes, it releases glucosinolate, a biofumigant that helps lower nematode populations. In addition, rapeseed is great for breaking up compaction and improving soil filtration. It has a really long taproot that will loosen the soil and improve the soil tilth. So for me, its doing a couple of jobs to help me improve the soil health of my vineyard. We also use it pretty widely as a cover crop before many of our crops for that reason.

Not only am I sampling for nematodes, but I am also sampling soil nutrient tests. So when I get the results back for the petioles, I know what nutrients were present in the soil at what levels and comparing that info to the nutrients in the petiole analysis, tells me what the plant is able to utilize from the soil. Many factors influence how a plant is able to utilize nutrients from the soil. Just because a nutrient is present in the soil, does not mean is is automatically available to the plant. Things like pH, moisture, temperature, the cation exchange capacity (CEC) of the soil, physiologic issues with the plant, and the nutrient must be in the chemical form that the plant can utilize. For example, plants can only utilize nitrogen in the form of ammonium or nitrate. Another nutrient, phosphorus, is only available to the plant if the soil pH is between 5.5 and 7. Outside those parameters, and the plant cannot take up phosphorus as well as other nutrients.

Sampling petioles
 Petioles are the stems of the grape leaf. At bloom, I want to sample the petiole across from the developing cluster. This will tell me what the cluster is receiving in vine nutrition by sampling the petiole across from it. The analogy I use is that this is like going to the doctor for a blood test. There's a lot of information we health care practitioners can gleen from lab results - plant or human.

My petiole samples separated in bags by variety.

Off to the Post Office with my samples!

Anxious to know my results for the petioles as it will tell me if I need to make any nutrient adjustments in the different varietal blocks. It will also give me a chance to compare the previous year's results to know what direction the different nutrients are headed in so I can see if my long term plant health and nutrition plan is working (see I can still be a dietitian, just with plants and soil instead of humans).

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