Innovation in new-type fertilizer technology still needs to deepen, and product quality needs to improve
At present, new-type fertilizers are becoming the focus of efforts in the chemical fertilizer industry, because they fit the new situation of agricultural development and also meet the needs of industrial upgrading. However, under enormous market pressure, some enterprises make only superficial attempts at technological innovation, contenting themselves with hyping new concepts and creating new gimmicks. Compared with agriculturally developed countries, China's path of fertilizer innovation is still very long, and the room for it is still very large.
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The application of slow and controlled release fertilizers is limited by multiple factors
It is not that control alone brings results
Among the family of new-type fertilizers, slow and controlled release fertilizers are undoubtedly one of the most important varieties. Since 2000, China's slow and controlled release fertilizer industry has entered a stage of rapid development. As of 2011, China had become the world's largest producer and consumer of slow and controlled release fertilizers, with output that year reaching 700,000 tons, followed by the United States and Canada, at 600,000 tons and 150,000 tons respectively.
For farmers, any new-type fertilizer must ultimately speak through its yield-increasing effect, and slow and controlled release fertilizers face exactly this problem. Domestic agricultural experts once conducted a controlled trial with a total sample size of 93, and the results showed that nearly half of the samples had flat yields, the proportion of samples with increased yields did not exceed 40%, and in addition 14% of samples had reduced yields. This survey data may feel markedly different from the commonly seen corporate promotional claims.
Why can't slow and controlled release fertilizers achieve results simply through control? The author believes that slow and controlled release fertilizers are not a cure-all; they are likewise restricted by multiple factors such as application region, crop, season and application method. In different regions and on different crops, the effects of slow and controlled release fertilizers vary greatly, and the level of fertilizer efficiency is determined to a large extent by application technique.
At the same time, in the manufacturing stage of slow and controlled release fertilizers, there are still many shortcomings that urgently need to be overcome. For example, for organic coated slow and controlled release fertilizers, the organic materials used as coatings are expensive and also bring secondary pollution; sulfur-coated slow and controlled release fertilizers will aggravate the degree of soil acidification, may not be suitable for acidic soils and vegetable gardens in the south, and in paddy fields will also bring hydrogen sulfide toxicity; and for slow and controlled release fertilizers using inorganic coatings, the biggest problem is that the control effect is difficult to guarantee. In addition, whether sulfur-coated or inorganic-coated slow and controlled release fertilizers, both have limitations on nitrogen nutrient content, which is not conducive to formulating high-concentration blended fertilizers.
In the technological innovation of slow and controlled release fertilizers, special attention should be paid to the research and development of natural and cheap slow and controlled release materials, such as oxamide, modified humic acid, polyglutamic acid, fermented alginic acid, etc. These materials all have good modification and efficiency-enhancing effects.
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Stabilized fertilizers in terms of crop yield-increasing effect
Are not necessarily stable
Stabilized fertilizers are actually also a kind of slow release fertilizer, except that they adopt the approach of chemical inhibition to slow the volatilization and loss of nitrogen. Stabilized fertilizers generally use two kinds of inhibitors——urease inhibitors and nitrification inhibitors.
Domestic research has found that the fertilizer utilization rate of fertilizers with added urease inhibitors is above 30%, about 5.2% higher than the nitrogen utilization rate of urea without urease inhibitors. After adding nitrification inhibitors, nitrogen fertilizer can remain in the soil in the form of ammonium nitrogen for a longer time, and ammonium nitrogen can be directly absorbed by crops, so the loss rate is greatly reduced.
However, stabilized fertilizers are not necessarily stable in their yield-increasing effect. Because the soil environment is changeable, urease inhibitors have not shown a stable yield-increasing effect in field trials. After synthesizing relevant data, foreign scholars concluded that in regions where crop yield potential is large, soil nitrogen levels are low, and both soil and environmental conditions are favorable to ammonia volatilization, applying fertilizers containing urease inhibitors will bring the greatest benefits.
Similarly, nitrification inhibitors also have a similar situation. Different soil fertility levels, different crop types, diverse nitrification inhibitor varieties and the soil itself and other factors will all lead to unstable yield-increasing effects of nitrification inhibitor fertilizers.
More importantly, stabilized fertilizers carry potential environmental risks. On January 25, 2013, New Zealand milk, renowned worldwide, was exposed as containing the toxic substance dicyandiamide. Later investigation revealed that some pastures sprayed fertilizers containing dicyandiamide to grow forage grass, causing the milk to be contaminated. In fact, dicyandiamide is one of the types of inhibitors in stabilized fertilizers.
It can be seen that in the development of stabilized fertilizers, developing more adaptable varieties and finding safer inhibitors should rightly become the focus of technological breakthroughs.