Nitrogen Deficiency in Tomato
Nitrogen deficiencies are characterized by a widespread chlorosis of leaves together with a light red discoloration of veins and petioles. Symptoms develop first in older leaves and move gradually up to the younger ones. In mild cases, the older mature leaves turn pale green. As the deficiency progresses they first become uniformly yellow, yellowish-white later (veins included). Leaf deformation may occur. Young leaves remain pale green and grow smaller than usual. Plant have a spindly aspect due to the reduced branching but their height is normal. Plants become more susceptible to water stress and the wilting of leaves is common. Premature death and shedding may happen. Recovery after application of nitrogen becomes evident after a few days.
High rates of nitrogen are important during the vegetative growth of the plant. In periods of favorable weather, it is important to provide the fast growing crops with a good nitrogen supply, so that they can reach their maximum fruit production potential. Nitrogen deficiencies can be observed in sandy soils with little organic matter as they are prone to leaching of nutrients. Frequent rainfalls, flooding or heavy irrigation wash down nitrogen into the soil and can also lead to deficiencies. Periods of drought stress hinder the absorption of water and nutrients, resulting in unbalanced nutrient supply. Finally, the soil pH also plays a role in the availability of nitrogen to the plant.
High levels of organic matter in soils can enhance soil structure and improve the capacity of the soil to retain water and nutrients. Organic matter can be added to soils as manure, compost, or peat.
Recovery of tomato plants after application of nitrogen becomes evident after a few days. Amendments can be done using products based on urea, ammonium or nitrate. Nitrogen is often provided as part of base fertilization products containing different rates of this nutrient together with phosphorus and potassium (the so-called N-P-K base trio). Several products are available on the market. The recommended grade depends on the soil type and the growth stage of the plant.