Q: My tomato plants are doing really well this year. I am giving them a small amount of liquid fertilizer and they are staked in a good sunny position. They are however getting really tall and spindly and I'm struggling to keep them from toppling over. Is there anything I can do to keep them growing too tall?
Congratulations on having good tomato plants this season!
It may be that the plants have enough fertilizer and water so they're growing vegetatively a little too vigorously. Since they're growing well, at this point they just need weekly watering and a couple of fertilizer applications during the rest of the growing season. Nitrogen is an important nutrient that tomatoes need early in their growth cycle, but after they start setting fruit, it’s important to cut back on the nitrogen because it will cause plant growth at the expense of fruit production. (Check the label on your liquid fertilizer and see what the nitrogen ratio is. For tomatoes, it should be a lower number than the other nutrients.) Once you adjust the water and fertilizer, the plants may still need some extra staking or trellising. This site has some good trellising ideas.
Additionally, you've probably noticed that when it rains, plants look greener and more lush than they do when you just irrigate them. Rain delivers nitrogen to the soil and when we have thunderstorms with lightning, this delivers even more nitrogen to the soil. This is because nitrogen in the atmosphere can be transformed into a form plants can utilize through the process of nitrogen fixation. Each bolt of lightning carries a strong electrical charge that is powerful enough to break the bonds of nitrogen molecules in the atmosphere. Once the nitrogen atoms are split, they quickly bond to oxygen in the atmosphere, forming nitrogen dioxide. In the clouds, cloud droplets and raindrops dissolve the water soluble nitrogen dioxide forming nitrates (the form of nitrogen that plants can utilize). The nitrates fall to the ground in raindrops and seep into the soil where with the help from the soil microorganisms found in a healthy organic soil, fix nitrogen to be absorbed by plants.
Our planet's atmosphere is composed of 78% nitrogen. Human bodies need proteins that contain nitrogen, but the nitrogen in the air is not readily available to our bodies to process, so our bodies evolved to get that nitrogen by eating plants (legumes and nuts) or animals that eat plants. This is why Native American farmers consider lightning sacred. They didn't need scientific evidence to understand that Nature gave us everything we need to feed everyone and be healthy and strong.