Analysis of Why Fertilizer Burn Causes Severe Soil Contamination

Fertilizer burn refers to the visible damage done to plants and soil when too much fertilizer is applied, or when fertilizer is applied in an overly concentrated way. Abusing fertilizer can cause severe contamination of the land. Here "fertilizer" means not only chemical fertilizers but also organic fertilizers! Although soil degradation is not caused only by severe soil contamination from fertilizer burn, there is no doubt that properly controlling fertilizer-burn contamination will help maintain a soil environment in which crops can grow healthily.

1. Causes of soil degradation

1. Heavy use of chemical fertilizers, which causes the soil to become compacted and airless.

2. Heavy use of poor-quality organic fertilizers, such as uncomposted chicken manure, sludge that has not been treated for heavy metals, and industrial by-products that have not been further processed.

3. Long-term continuous cropping of a single crop, which causes replant problems.

Among these, the heavy use of poor-quality organic fertilizers is by far the most harmful.

2. Causes of fertilizer burn

1. Blind application of nitrogen fertilizer.

In production, people always assume that crops have a large demand for nitrogen fertilizer, so whenever a crop grows poorly, they apply nitrogen regardless of what is actually lacking; the more nitrogen they apply, the more it builds up, leading to nitrogen excess and fertilizer burn. This is especially true for volatile nitrogen fertilizers such as ammonium bicarbonate and ammonia water, which easily cause fertilizer burn in crops; applying too much nitrogen fertilizer can also cause nitrate accumulation in plants and yellowing of the leaves. Applying too much nitrate nitrogen fertilizer easily causes chlorosis and molybdenum deficiency in crops.

2. Applying too large a topdressing amount.

Applying too large a single dose of chemical fertilizer causes the fertilizer concentration in the soil to become too high, which blocks the crop roots from absorbing nutrients and water, resulting in fertilizer burn.

3. Applying uncomposted organic fertilizer.

During decomposition, uncomposted organic fertilizer produces large amounts of organic acids and heat, which easily causes root burn.

4. Topdressing placed too close to the crop roots.

Because chemical fertilizers break down quickly and have a strong effect, using them as topdressing too close to the roots easily causes fertilizer burn in crops.

3. The harm of uncomposted organic fertilizers such as chicken manure that have not been thoroughly sterilized or treated to kill insects and eggs

1. An increase in soil-borne diseases

Manure often contains large amounts of bacteria, parasites and insect eggs. If it is not thoroughly composted, sterilized and treated to kill insects, these bacteria and parasites will be carried into the soil and damage the crop roots.

In addition, manure contains pathogens and pests such as coliform bacteria and nematodes; using it directly will lead to the spread of pests and diseases, cause crops to become diseased, and also affect the health of people who eat agricultural products; when uncomposted organic matter ferments in the soil, it easily breeds pathogens and pests, leading to plant pests and diseases.

2. Heat released during fermentation causes root burn and seedling burn

Organic fertilizer releases heat during fermentation, so organic fertilizer is fully fermented before it leaves the factory. If it has not been fully fermented, then after being applied to the soil it will ferment in the soil and release heat; because it is in direct contact with the roots, this can damage the roots, thereby affecting crop growth and increasing crop diseases.

When the roots are damaged, nutrition will be incomplete, and when nutrition is incomplete, immunity will be low. These things are all interconnected.

3. Damage to the roots from harmful gases such as ammonia

During fermentation, livestock manure easily produces harmful gases such as ammonia, which harm root growth and at the same time turn the pH of the root environment acidic.

Untreated industrial by-products and incompletely treated sludge organic fertilizers generally contain excessive heavy metals; at the same time, some by-products have a high chlorine content, sometimes as high as 9%, and long-term use will cause soil acidification. It will inhibit crop growth, and some by-products and sludge organic fertilizers even have extremely low nutrient content.

4. Noticeably slow fertilizer effect

Most of the nutrients in unfermented and uncomposted organic fertilizer are in organic or slow-release forms and cannot be directly absorbed and used by crops; only after being broken down and converted into fast-acting forms can they be absorbed and used by crops. Therefore, applying it directly without fermentation will slow down the fertilizer effect.

4. Preventive measures

1. Do not apply uncomposted organic fertilizer.

Organic fertilizer must be composted before application; poultry manure in particular should be fermented and then mixed with chemical fertilizer before use.

2. Use chemical fertilizers rationally.

Before use, they must first be measured and applied according to concentration; in particular, nitrogen fertilizer must not be applied in excess at one time. The concentration for foliar spraying should not be too high; when urea is used as a foliar fertilizer, the concentration should not exceed 0.3%, and it is enough to spray until moistened.

3. Apply more organic fertilizer.

Organic fertilizer applied to the soil has a strong adsorption capacity for cations, keeping their concentration from becoming too high and improving the soil's nutrient-buffering capacity, which can greatly reduce the occurrence of fertilizer burn.

4. Fertilizing should be about 10cm from the crop roots, and it should be applied deeply.

After topdressing, cover the soil immediately to prevent seedling burn during the seedling stage and loss of fertilizer effect. If the soil is dry, topdressing requires timely irrigation to lower the concentration and avoid seedling burn.

The roots are the key to the crop, and the soil is the growing environment for the roots. A good soil environment lets the roots grow healthily, and good roots let the crop grow healthily. So everyone should learn to take care of the soil and improve the root environment.