Soil test results told a different story. Howard broached the issue with Knox, who pointed out that the soils in Howard’s fields were a patchwork mix of a red clay and a gray, sandier soil. These soil types had different capacities to retain phosphorus. Knox suggested that Howard should consider using the poultry house litter from his own farm for areas needing extra phosphorus.

Howard was hesitant. He knew the litter would be a good source of phosphorus, but he was afraid it would provide too much nitrogen for strawberries. Cautiously, he put out litter in the fall nearly a year before planting strawberries. That winter and spring, he let a neighbor grow barley in the field to deplete some of the nitrogen. The strawberry crop did not incur any problems with excess nitrogen.

Howard is glad he followed up on Knox’s recommendation. His current routine is to apply litter to a ryegrass cover crop in March or April when the layer houses are cleaned out. He still likes the fact that the ryegrass cover crop uses some of the excess nitrogen before strawberries are planted in September. And after strawberries are harvested, he can plant yet another crop — pumpkins — directly into the existing plastic.

The amount of litter the Howards apply depends jointly on the results of the waste analysis and soil test reports. Due to the different soil types, they often spot-apply commercial fertilizer — putting it out only where it is needed based on soil test results. Before planting, they also use a nematode assay to establish whether pre-plant treatment is necessary and solution analysis to check the pH and salt content of their irrigation water source.

“Plasticulture is a hard job and a big expense,” Howard said. “The farmer is dependent on an entire system working. If it doesn’t, he could lose his whole crop. It pays to take precautions. I’m not a gardener. I need to make a living.”

Knox said tissue analysis is one of the best tools available to plasticulture growers.

“Test results are available within a couple of days and give a precise snapshot of the nutrient needs of each crop,” Knox said. “The test can even detect deficiencies before symptoms appear and losses occur. For high-value, intensively managed crops, tissue testing is the best way to optimize fertilizer input costs and obtain desired yields. It is particularly useful for Mike since he grows two successive crops on plastic. By monitoring nutrient use with tissue testing on a bi-weekly basis, he knows exactly how and when to adjust fertigation.”

The Howards are firm believers in the benefits of agronomic testing. But even more than the testing, they appreciate being able to talk to a real person about what their report results mean.

“The good thing about working with regional agronomists is that they know all about sampling procedures, test results and nutrient management,” said Howard’s son Brian, “and . . . they answer their phone after hours.”

The NCDA&CS Agronomic Division has 13 regional agronomists who are striving to lend special assistance to plasticulture growers this year. Thanks to a grant from the North Carolina Tobacco Trust Fund Commission, the Division has been able to hold two plasticulture training workshops, offer growers free vouchers for plant tissue analysis, and offset the travel costs involved in on-site visits by regional agronomists. Growers with an interest in plasticulture are encouraged to contact their regional agronomist for advice. Visit for contact information.