Published: August 24, 2007 11:07 pm            

Area farmers look to irrigation

Browned and withered corn crops, extreme heat and a record-breaking drought brought agricultural experts, farmers and gardeners together Tuesday evening under the shade of pecan trees at the North Alabama Horticulture Experiment Station to hear a talk by an irrigation specialist.

Before the meeting started Tim Scott, Cullman County Soil and Water Conservation District project manager, pointed to a corn crop and said it will only yield about 35 bushels an acre. Normal yield is 85 to 100 bushels per acre.

“That right there, we would normally pick at the end of September,” Scott said. “We will pick it in a week to a week and a half.”

Tom Williamson with the North Alabama Agriplex Committee said he didn’t remember a time when agricultural experts and farmers had to have a meeting like this.

“We are the No. 1 agriculture county in the state,” he said. “It is so much a part of our lives.”

Williamson said the goal of the talks was to improve profits and stay in business.

“Everybody is pulling together because they know how important it is to them,” he said.

Robin Franks, district sales manager with Netafim, was the keynote speaker. He is from South Africa originally but currently lives in the United States. He has taught irrigation and designed systems worldwide for 45 years. He also spoke with an accent.

Drawing immediate laughter from the crowd, Franks said, “We’ve got to get the rules straight for us. Alright. You all have got a really bad accent. Okay. You have no idea how bad they are.”

Netafim means “little drops of water” in Hebrew.

“A lot of the world is not blessed with a lot of water, and this year unfortunately and a little bit last year, you’ve experienced some of the conditions that prevail in parts of Africa where I am from,” said Franks.

Franks said said he wanted more about irrigation than a specific drip irrigation system. If growers understand irrigation, then they can move toward planning an irrigation system.

“First of all, how many of you are irrigating now?” he said. “Quite a few of you. How many of you plan your irrigation? Not too many.”

The first rule is it takes 100 gallons of water to make 1 pound of sugar, Frank said. The sugar can be a gallon of orange juice or a bag of tomatoes.

“What this means is that each plant needs a requirement of water to produce its optimum yield,” said Franks. “When we talk about irrigation practice, we need to insure that we provide the plant with this 100 gallons of water, and it’s just a figure, sometimes more, sometimes less.”

Growers tend to do a number of things wrong including over irrigating, under irrigating or planters tend to have a poor system and while they water, there is runoff. There is also something called depercolation. In normal plant growth, water percolates below the ground and then evaporates off. In depercolation, the process is hindered.

“We put the water on for so long or misapply those that are on sandy ground so the water is beyond the root zone,” said Franks.

Franks talked about field capacity.

“That means the water stops going into the ground or the bucket is full,” he said. “Field capacity means when all the soil pores in that bucket are full or all the air is out of the water.”

Once oxygen depletion occurs, the plant stops growing. Franks called this stage the minus oxygen stage.

The other extreme is the wilting point.

“That is at the point when that plant falls over because it can’t get any more water out of the soil,” said Franks.

Franks called this stage the minus H2O stage.

Taking a question from Festhalle Market Platz exhibitor Beth Haynes, Franks said of the H2O stage, “Once you’re beyond that, you are in the compost business,” drawing more laughter.

Fifty percent of the time, growers are somewhere between 70 and 90 percent of the field capacity for their soil.

“The goal of a good irrigator is to have targeted moisture,” said Franks.

In the beginning, growers irrigate with a higher regime because plants are in the vegetative stage.

“We want to encourage the plant to be healthy and grow up; and then as we reach maturity, we will start reducing the water somewhat,” he said.

The goal is to give the plant what it needs each day.

“What that means is in this root zone of your crop, you have oxygen. As soon as that oxygen is in the plant, that plant will start growing, photosynthesizing and moving,” he said.

Franks said growers need to wait for the water to percolate below their crop and then to evaporate it off.

“If we leave room for the plant to grow while we’re watering it, we’re going to get better productivity,” said Franks. “We’re also going to reduce the wastage.”

Planters need to keep in mind what happened yesterday when thinking about how much water to add today.

“We now get into this adding to that 100 gallons of water. We’re short of water. This is the basis of all irrigation design worldwide,” said Franks.

Based on USDA research, the sun burns off 3/10 of an inch of water a day, said Franks. That translates into approximately 9,000 gallons of water a day.



Following the Numbers

When planning irrigation, growers need to plan where the plants will be placed. If a plant is in 1/3 canopy as opposed to 2/3 canopy or full canopy, it will lose less water than the other two stages.

“If you watch on a really hot day, when you go back to water your crop and it’s only 1/3 canopy, it does not need as much as your crop at full canopy,” said Franks.

Broad leaf and grasses requires 80 percent of what the sun burns off. Corn, maize and sweet corn require 100 percent water replacement.

“So if you’re losing 3/10s of an inch, the sun burns off 3/10s of an inch, you need to put 3/10s of an inch back into your crop,” said Franks. “But if you put that same 3/10s on your cabbages, you’ll flood them because they don’t use that much water.”

Cotton is 80 percent of corn.

“If you irrigate corn at 1/3 inch a day, you would only put 80 percent of that back on a cotton patch,” said Franks. “That is why cotton is very favorable. It uses less water.”

When watering lawn around the house, homeowners need to put 4/10s because of the amount of leaf matter they are dealing with, said Franks.

If your planning a garden, don’t mix your crops because they have different water requirements.

“If you get 1 inch of rain on 1 acre, you’ve got 27,154 gallons. If the sun bakes off 1/3 of that today, that is 9,000 gallons,” said Franks.

He explained how to size an irrigation system.

The primary number for irrigation is 450 gallons per minute which equals 1 inch per acre per hour or 24 inches in 24 hours.

“If you are planning a crop in this environment here where we need 1/3 inch per acre per day, if we have 450 gallons, the smart farmer would never design for more than 76 acres of irrigation. You can’t stretch the water,” said Franks.

If a grower can only get 15 gallons of water a minute out of the city water supply pipe, then multiply 15 by 60 minutes by 24 hours which equals 21,600 gallons.

“That will tell you exactly how much water you have available to you and the size of irrigation accordingly,” said Franks.

        

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