The effects of slowly available nitrogen fertilizer, the nitrification inhibitor-added fertilizer, and block fertilizer are recognizing to have high effects. Hence, these days they are available in markets as commercial products.
Since 1960, to enhance the agricultural production, countermeasures are available for promotion of horticultural farming. The results of soil management and fertilization experiments are combing and systematizing for practical application. Hence, they are contributing to increase of agricultural production, both in quantity and quality. The main countermeasures are the improvement of fertilization, maintenance of soil fertility, and the adequate treatment against growth injury.
A very significant effect is seen in drill deep fertilization and the hole fertilization method. In these cases development of the root system and the absorption of nutrients greatly differ from others. And the methods are very promising for improving the techniques.
In connection with them, the effect of the slowly available nitrogen fertilizers, the nitrification inhibitor-added fertilizers and block fertilizers are recognizing to have high effect and now they are in market as commercial products.
Recently, the culture of vegetable in green houses and plastic film houses have become popular. The conditions of force culture differ from that of field culture. It is happening, especially, due to heavy fertilizer application and also due to the fact that leaching does not take place so much.
Another reason is the air inside green houses and plastic films tends to be high in temperature and dry. Thus, salt is easily accumulating at the soil surface. So that, the yield and the crop quality is declining. This decline is mainly due to the salt injury, gas injury, successive culture injury and diseases.
The basic countermeasure is the rationalization of fertilizer application. This is almost confirm now in combination with countermeasures against salt injury and diseases. But there are several other problems which are yet to resolve. These problems are about successive culture injury and sick soil which are left for future study.
New fertilizers are widely using for horticultural crops. This can be seen in case of rice culture, where farmers are obtaining greater efficiency by using them.
For instance, if a comparatively large amount of the above-mention new fertilizer are applying as basal application, salt injury will not occur. This result is recognizing as effective basal application, which is ideal fertilization, and causing decrease time of additional fertilizer application.
Matching culture technique
In modern times, the matching culture using plastic film is spreading rapidly. This method creates many effects such as; rising of temperature, maintenance of soil water, weed control and protection against soil coagulation and leaching of nutrition. The application of new type fertilizers is also very effective in this method.
Soil sterilization is becoming a useful agricultural technique for the prevention of continuous cropping injury including plant diseases. It is divided into two main methods; one is steam sterilization and the other is by agricultural chemicals.
Soil sterilization may have some deteriorative effect on the subsequent plant growth due to nitrogen transformation. For instance, the rice yield increasing by applying only one-half nitrogen fertilizer with chloropicrin-treatment on paddy field. Or young shoot may die after transplanting on steam sterilization soil.
This phenomena is causing by steam sterilization are attributing to the accumulation of nitrogen fertilizer and nitrate nitrogen; pH values of soil and excess of manganese. It is clear that the deteriorative effect may prevent by decreasing the amount of nitrogen fertilizer, calcium and organic fertilizer before steam sterilization. Experts recommends moderate application of nitrate nitrogen fertilizer after the treatment.
Due to the large varieties of crops culture, many points are uncertain. Thus, the ideal technique may not establish yet. This is a big challenge for future studies.
In horticulture, such as vegetable crops, flowers and fruit trees – the application of liquid fertilizer serves both as a fertilizer and water. It has merit that decreases salt injury and saves fertilizer application labor. The application of liquid fertilizer is gradually getting popularity.
The past studies on the technique of fertilizer application were solely focusing on increasing crop productivity. But these days it is more focusing on quality enhancement and improving nutrition. In future, further investigation and development of new techniques is necessary for progress in quality and nutritional diagnosis.