Yes, you can sprinkle fertilizer on top of soil and it works for many crops. The key is watering well after so nutrients move down to where your roots can reach them.
I tested both methods in my own beds two seasons ago. Half got surface feeding while the other half got the same amount mixed into the top few inches. The results taught me when each method works best for different situations.
Surface fertilizer application works great for your plants with roots in the ground. Your tomatoes, peppers, and other growing crops grab nutrients as they wash down. This method saves you time and avoids root damage from digging near your plants.
The science behind this is simple. Nitrogen moves through soil fast when you add water. A good soak after top dressing garden beds pushes nitrogen right down to where roots wait. Your plants can use it within a few days.
Phosphorus acts different from nitrogen in your soil. It stays put near where you drop it and moves slow over time. Surface spread phosphorus takes months or years to reach deep roots. Mix it into soil before planting if your dirt needs it.
New transplants and direct seeded crops do better with fertilizer mixed in. Young roots sit near the surface and need food right where they grow. You need to work fertilizer into the top 4-6 inches (10-15 cm) of soil before planting new beds.
My test beds showed about 20% better growth when I mixed fertilizer in. This held true for the first month only. After your plants mature, surface feeding catches up fast. Grown roots spread wide enough to find nutrients wherever they land.
Water makes surface feeding work or fail for you. You need to soak your beds well within a day of spreading granules. A light misting does nothing for moving nutrients down. I use my drip system for 30-45 minutes right after each surface application.
Hot dry weather calls for extra care with surface application. Granules sitting on dry soil can burn your plant stems if they touch. Keep a gap of 2-3 inches (5-8 cm) between fertilizer and plant bases when you top dress.
Rain right after surface feeding is ideal but risky to time. A gentle rain washes nutrients down while a heavy storm washes them away from your beds. Check your forecast before you spread fertilizer on top of the soil.
Slow release granules work better on the surface than quick release types. They feed your plants over weeks instead of dumping all nutrients at once. I switched to slow release for all my surface work and saw steadier growth with less burn risk.
Read the full article: Fertilizing Vegetable Garden: Boost Your Harvest
