Investigation of Potential Climatic and Nutritional Causes of Grape Chlorosis
- Research Status: Completed 2005
Joan R. Davenport
Robert G. Stevens
Analysis of six different vineyards with varied chlorosis histories was examined for climatic and nutrient soil and petiole deficiencies across four growing seasons. Researchers found that grape chlorosis is associated with high soil moisture at bloom. In addition, both surface and root zone soil temperatures were lower in chlorotic locations than in non-chlorotic from bud break through the bloom period. The data collected on both soil moisture and temperature combined all years and sites, and therefore makes a very compelling argument that cool moist soil conditions early in the season are triggers for chlorosis.
From a vine and soil nutrition analysis sites with chlorosis were found to have higher soil calcium (Ca) and magnesium (Mg) concentrations and lower iron (Fe), manganese (Mn) and aluminum (Al) concentrations than non-chlorotic sites. Both leaf blade and petiole tissue Mn concentrations were lower at chlorotic locations, which is consistent with the pattern of soil Mn. However, tissue Al concentration was slightly higher in chlorotic vs non-chlorotic sites, which is inverse to the pattern in the soil. It is noteworthy that these tissue nutrient concentrations are of unaffected tissue. Analysis of affected and unaffected tissue from sites with chlorosis did not show any nutrient concentration differences. Mn would be expected to be more available in the wetter (reducing) conditions associated with chlorosis. The research finds that the cool, wet conditions potentially impede new root development and subsequent nutrient uptake. Additionally, nutrient concentrations of Ca and, to a lesser extent, Mg which can interfere with Mn uptake (which plays an essential role in photosynthesis or ripening of grapes) need to be monitored and adjusted in cool wet Springs.
