How to feed your crops

If you have a soil bed which you’ve treated with high-quality organic matter, then the need to feed your plants is greatly reduced. Good soil quality, in terms of structure, is the backbone of growing plants. Only once you have this established, can plant food be added to your routine. This is much like supplementing a diet with vitamins which may be lacking from your normal intake.

Plants require more nitrogen than any other nutrient as it’s a vital component of chlorophyll, used for photosynthesis.

However, the only way that plants can absorb nitrogen from the soil is if it’s in mineral form.

And these only make up 2% of the nitrogen present in the ground.

The other 98% is nitrogen stored in organic forms. Soil microorganisms convert organic forms of nitrogen to mineral forms.

They do this when they decompose organic matter and fresh plant residues. This is called mineralising.

You can see why most gardeners aim to boost the number of microorganisms living in the soil through soil conditioning. The fastest way to do this is by adding compost, manure, plant cuttings, or wood chip mulch into the soil. This is food for the microbes and will boost their activity as well as the levels of minerals they excrete.

We now know that soil conditions are proven to affect the plant’s ability to provide us nourishment, too. A healthy plant makes for hefty doses of nutrition given to us at dinner time. Nitrogen is a necessary component of several vitamins, so our food’s vitamin content is made from the ground up. Research also suggests that food grown to be larger and faster producing may have lower nutritional content. There’s also evidence that suggests soil tainted with chemicals or pollutants will struggle to produce its highest potential yield.

Sufficient all-around plant health is necessary for it to produce enough energy, much like humans need.

And this especially applies when it comes time to divert resources for fruiting. This means your plant’s health will contribute towards how your crops look, how large they grow, and how good they taste.

With this in mind, studies have shown that plants stressed by disease are often more susceptible to insect damage.

So, poor soil conditions can have knock-on effects far greater than you might believe. Luckily, you can prioritise plant health through soil care.

When we feed our crops, we cut into the end part of the mineralising process to boost levels of mineral nitrogen for plants to take up immediately. This means fast results for your plants. Try to think of the soil as a bank. Withdrawals are made by the plant from the soil (like mineral nitrogen) much like we would from a bank account.

The pool of unused soil nutrients (like organic nitrogen) is like a savings account.

When bank funds are low, transfers are made from savings.

When a bank account is flush, resources can be moved to savings for long-term retention.

Soils do this with excess nutrients, binding some to the soil to become temporarily unavailable as insoluble minerals.

These can be dissolved again later when needed.

NPK formulas make up most of our garden feeds because these are the three most beneficial nutrients for plant growth.

And they aren’t always naturally accessible. Nitrogen has been shown to affect the quality and quantity of dry matter in leafy vegetables and protein in grain crops.

Phosphorus is known for its sun-harnessing capabilities. Using energy from the sun to put down root growth and support new shoots.

Finally, research by Colorado State University PhD soil microbiologists suggests that potassium is considered second only to nitrogen when it comes to nutrients needed by plants.

And it is commonly considered as a “quality nutrient”. This helps to finish crops that need a little extra to get them across the line.

Some nitrogen-fixing bacteria, such as Rhizobium, live in the root nodules of legumes. They form a mutualistic relationship with the plant, producing ammonia in exchange for carbohydrates.

Legumes may divert up to 30% of their energy to the root zone to make food for microbes. This is why it can be a good idea to plant legumes in plots in need of a nutrient boost.

If you are not regularly feeding plants, and instead relying on the 2% of mineral nitrogen that’s naturally available, there’s no guarantee that your plants are actually receiving this. Coarse textured soils may leach nitrate, so alternative supplies (given by hand) can be useful to supplement the stores for hungry plant roots.

Now, you can buy products with specific needs in mind. Superphosphate offers a feed solely rich in phosphate for fruit and veg ripening, while Miracle-Gro® All Purpose concentrated plant food is a great all-round product that delivers a higher nitrogen level NPK ratio for flowers and veg in pots or beds.

Soil texture contributes to whether nutrients leach out through the bedrock layer into waterways. Thus, wasting vital mineral sources, so misuse of fertilisers may cause environmental and water quality issues.

Generally speaking, sandy soils can be given a moderate nitrogen supply, while loam and clay soils are most suited to a high soil nitrogen supply.

Due to the complex eco-system that lives within our garden soils, little and often or slow release products during the growing season is the best policy.