Effects of Different Organic Fertilization Regimes on Soil Physicochemical Properties and Bacterial Community Assembly to Promote Greenhouse-Cultivated Aloe vera Growth

Imagine the soil beneath our feet not as just dirt, but as a bustling, invisible city. In this city, tiny living creatures called bacteria are the workers, the builders, and the recyclers. They break down food, recycle nutrients, and keep the environment healthy for the plants growing above them. Just like a human city needs good roads, clean water, and plenty of food to thrive, this underground city needs the right conditions to keep its population diverse and its workers happy. When we grow plants in greenhouses, we are essentially managing this city. If we feed the plants the wrong way, we might accidentally starve the bacteria or build a city where only a few types of workers survive, making the whole system fragile.

One of the best ways to feed both the plants and the bacteria is with organic fertilizer—think of it as a gourmet meal made from natural leftovers like compost or manure, rather than a chemical supplement. But here's the big question: does it matter what kind of organic meal we serve? Does a standard compost work the same as a special mix made just for a specific plant? Scientists have long known that organic fertilizer is good, but they haven't fully understood how different types of these "meals" change the bacterial city over a long time, especially for a plant that is famous for its healing powers: Aloe vera. This plant is used in everything from sunburn creams to health drinks, but to make good Aloe, you need healthy soil.

A team of researchers decided to play the role of "soil chefs" to find out which recipe works best. They set up a four-year experiment in a greenhouse in China, growing Aloe vera plants under four different feeding plans. They compared a control group that got no fertilizer at all against three different types of organic fertilizers: a standard "conventional" mix, a special "Aloe-specific" mix, and a unique "earthworm manure" mix. They didn't just look at how tall the plants grew; they dug into the soil to see how the bacterial city changed. They measured the nutrients in the dirt and used high-tech DNA sequencing to count and identify the different types of bacteria living around the plant roots.

The results were like discovering that the earthworm manure was the "superfood" of the soil world. The study found that while all the fertilized plants grew better than the ones with no food, the plants fed with earthworm manure (called the QY treatment) were the champions. These plants grew significantly taller—reaching 39 cm compared to 28 cm for the unfertilized plants. More importantly, the soil itself transformed. The earthworm manure treatment boosted the soil's organic matter by 40.76%, essentially turning the dirt into a much richer, more fertile environment.

But the real magic happened underground. The researchers discovered that the earthworm manure didn't just feed the plants; it threw a massive party for the bacteria. The soil treated with this manure had the most diverse and abundant bacterial community. It was like the difference between a quiet town with only a few families and a vibrant, bustling metropolis with people from all walks of life. The study showed that this specific fertilizer encouraged a wider variety of bacterial species to move in and set up shop, creating a more complex and resilient ecosystem.

The scientists also figured out why this happened. They found that the amount of organic matter in the soil and the availability of phosphorus (a key nutrient) were the main drivers that decided which bacteria would live there. The earthworm manure treatment created the perfect balance of these ingredients, acting like a master key that unlocked the door for a diverse bacterial community. Interestingly, while the plants fed with earthworm manure grew taller, they actually had slightly narrower leaves and crowns compared to the unfertilized plants. This suggests that the plants were putting all their energy into growing upward rather than spreading out sideways, likely because the rich soil gave them the resources to shoot for the sky.

In the end, this paper suggests that if you want to grow healthy, thriving Aloe vera in a greenhouse, you shouldn't just throw any old fertilizer at it. The specific type of organic food matters a lot. The earthworm manure treatment proved to be the most effective strategy, not only for making the plants taller but for building a stronger, more diverse underground bacterial city that supports the plant's long-term health. It's a reminder that in the world of farming, sometimes the best way to feed the plant is to feed the invisible city living right beneath its roots.