This situation in tomato, cucumber and lettuce is unexpectedly due to poisoning caused by excessive boron fertilization.

Boron is an indispensable trace element in crop growth. Many plants that are sensitive to boron, such as tomatoes and cauliflower, will grow poorly in boron-deficient land, or even reduce their yields.

However, too much boron can also cause poisoning, such as chlorosis, yellowing or scorching of the middle and lower leaves, and brown spots or patches on the leaf surface. Let's take a look at the specific manifestations and solutions of excessive boron in these three common vegetables.

Manifestations of excess boron:

Tomato: scorched brown necrotic spots appeared on the leaf margin and part of the mesophyll of the middle and lower leaves, and developed from the lower leaves to the upper part, and the whole plant withered in severe cases.

Cucumber: the edge of the middle and lower leaves is golden, sometimes brown spots appear on the leaf surface, and the growth of the terminal bud is inhibited, browning and dying in severe cases.

Lettuce: the middle and lower leaf margin is green and yellowing, and white or brown spots appear. In severe cases, the leaf margin is scorched and broken, and the leaf vein is dark brown.

Solution:

For the prevention and control of excess boron, boron damage can be alleviated by using lime, solidifying and reducing boron activity. The effectiveness of boron will decrease during drought, so applying too much boron to control watering can reduce the movement of available boron, avoid and reduce boron poisoning and retting roots.