Nitrogen is one of the most important nutrients required for optimum crop growth and high tomato crop yields. Tomato crops remove around 2.2-2.4kg for every tonne of fruit produced, therefore high rates of 250kg/ha or above are needed for average 100t/ha field crops. However, too much nitrogen can depress tomato yields, so it is important to confirm rates following local trials.
A balanced crop nutrition throughout root development, early growth, flowering and fruiting is fundamental in achieving high marketable tomato yields. High field yields are obtained on freely drained soils where water is not limiting.
Crop nutrition is also essential for increasing tomato yield.
Crop Nutrition and Tomato Yield
Correct form is critical, ammonium can restrict growth and adversely affect overall quality.
Phosphorus is important for early growth and root development of the establishing seedling. It is also essential at the stage of fruit set. In soils with low available phosphorus, fertilizer phosphate increases tomato fruit yield and ripening, reducing the number of rejected fruit at harvest.
Tomatoes have a relatively high potassium requirement with over 300kg/ha of potassium typically being utilized. High potassium levels provide high tomato yields. Balance to other nutrients such as calcium and magnesium is also important.
Calcium is required in the tomato for canopy growth, root development and yield. Mid-season availability is critical for high tomato crop yield. Continuous supply throughout the season is also important, balanced along potassium and magnesium.
Sulfur is important for overall tomato yield. Sulfur application is required throughout the whole season. Soils are often sulfur-deficient: Foliar applications can be more effective than soil applied fertilizer.
Unavailability of any micronutrients will limit tomato yield. It is important though to make sure that manganese and boron are not present in excess as this can lead to toxicity and restricted growth. The most important micronutrient is boron, which if in short supply, will result in fruit with corky areas on the shoulders and in severe deficiency instances may restrict fruit formation.
Other Crop Management Practices Influencing Tomato Yield
- Plant density and spacing are critical to ensure crops make the best use of environmental, especially light conditions, so that tomato yield potentials are reached.
- Maintenance of optimum soil pH ensures nutrients are readily available. The use of herbicides or cultivation will remove any weed competition.
- Temperature and light intensity are critical at flowering to ensure unhindered flower formation, good pollination, fertilization and fruit set.
- High temperature stress can lead to bud abscission prior to flowering. The same conditions at flowering will lead to abnormal flower development and death.
- Growers can minimize the competitive effects of excessive vegetative development by leaf pruning – most commonly by removing the lower leaves to allow more light to reach the ripening fruit. This also provides better air movement around the lower stem, reducing the impact of stem disease. It is important to avoid excessive leaf pruning in high light environments as the crops can be at risk of sunscald.
- Carbon dioxide enrichment in greenhouse corps increases individual fruit weight and total tomato yield. This is especially true in greenhouses with limited ventilation.
- The control of salinity by good leaching practices within the root environment and water supply management will maximize growth and ensure good nutrient availability.