| At present our country chemical fertilizer use is still at a high input and low utilization rate of the primary stage, every year, In our country, the chemical fertilizer investment is about50%of all the agriculture productive expenditure; however, fertilizer nitrogen utilization rate is only20%-40%. Since the nineteen eighties, the appearance of slow controlled release fertilizer had solved this problem and provided a new idea and effective way. Slow release fertilizer not only controlled the nutrient release rate effectively, but also can prolong the period of fertilizers affection,meet crop nutrient needs through the whole growth period, maximize the utilization rate of fertilizer, increase the economic benefits of fertilization. Slow controlled release fertilizers can be divided into two kinds, temperature dependent and moisture dependent. In our country’s present stage,the successful development of slow and controlled release fertilizer kinds are mainly for temperature dependent, moisture dependent accounted for a few.However,in the vast northern semi-arid climate agricultural area of our country, its agriculture is mainly developed by rain, and this urgently needed a kind which can apply to semi-arid regions of fertilizer varieties.In view of this, this test,which is simulated under the condition of water shortage in arid area and contrasts the fertilizer efficiency and biological effect in low cost, low residue, degradation of water soluble felted and coated fertilizer which is developed by Beijing Academy of agriculture with that in some most commonly used varieties of fertilizer in modern agricultural production biological, studies the fertilizer nitrogen stripping mechanism of transformation and effects on plant and soil nutrient absorption. This test provides a scientific basis in future for development of suitable slightly water soluble fertilizer which are apply to arid and semi arid areas. The results show that:(1) this study uses" indoor soil mix-incubation experiment" to explore slightly water soluble felted and coated fertilizer nitrogen release rate by constant temperature and controlling the different soil moisture content, temperature and soil moisture. The results show that, the common urea peak period is in seventh days;slightly water soluble felted and coated fertilizer peak period is about forty-second days, which is more than35days late for urea peak period.From here we conclude that compared with urea, slightly water soluble felted and coated fertilizer already has a sustained release effect. No matter how much soil moisture is, urea treatment always has a sharp decline after its peak.after the peak,especially after the55D, the nutrient content which urea can provide is so low,that can not continue to provide nutrients for crops, which needs to use the Topdressing Urea Applied in measure again. But slightly water soluble felted and coated fertilizer nitrogen stripping in the peak first decreasing rate is low, because the water content of soil, can be maintained in the1000-4000mg/kg level, that is to say plant growth nutrients are needed again, without topdressing, time-saving and labor-saving; secondly, the fertilizer nitrogen leaching amount, except at6%moisture content under microaerobic conditions water soluble felted and coated fertilizer cumulative total is slightly less than the urea treatment, in14%and22%moisture condition were significantly higher than the urea treatment, its numerical range;6961-12473mg/kg, described in the fertilizer utilization rate, compared with urea, slightly water soluble felted and coated fertilizer also have certain improvement to improve the utilization rate of the fertilizer, and reduce fertilizer nutrient loss on soil and environmental pollution. As in the70D after the sampling measurement of fertilizer nitrogen leaching rate has reached the nitrogen content of80%, it can be believed that a period of the fertilizer release is70days, which can provide the necessary nutrient crop stability for the vegetative whose growth period is70days. Peak of slightly water soluble felted and coated fertilizer appearers on the forty-second day, and whatever the waters level is, the fertilizer has obvious sustained release effect. In the condition of low temperature, soil moisture content on the fertilizer nutrient release plays the dominant role; the higher soil water content is, the higher fertilizer nitrogen stripping ratio will be, so as the fertilizer efficiency. At normal atmospheric temperature and high temperature, both temperature and moisture affect the nutrient release rate of common fertilizer, but the higher soil moisture still contributes to the fertilizer nutrient release. In the same water treatment conditions, temperature has a great impact on the fertilizer nitrogen release. When the water content is low, fertilizer nutrient release has substantially positive correlation whit temperature. When the soil moisture conditions is moderate, the fertilizer nutrient release affected by temperature and moisture, and it has positive correlation with soil temperature in early stage, after the25d temperature would inhibit the nutrient release. In the higher soil moisture condition, the fertilizer nutrient release can achieve optimal results when soil temperature at about25DEG C, but the peak period comes ahead of time. Thus, the optimal environment of nutrient release in slightly water soluble felted and coated fertilizer is25C soil temperature+14%or so soil moisture.(2) this study uses" soil column leaching experiment" by simulating natural rainfall condition, explored release effect mechanism of slightly water soluble felted and coated fertilizer in semiarid climatic conditions in different texture soils with rainfall and nitrogen release. The test results show that, compared with common urea, in sandy loam, nitrogen leaching rate of slightly water soluble felted and coated fertilizer was higher by0.5-1percentage points, in medium loam, it was lower by16.5percentage points. The starting and ending time would be delay of2-5days than common urea,and the time of peak value was delayed for15to20days. After the peak, slightly water-soluble fertilizer still has slow dissolution of nitrogen, which can be higher1-6percentage points than urea; this shows that the slightly water soluble felted and coated fertilizer nitrogen release has a slow release property. Compared medium loam with sandy loam, rates in each medium loam soil nitrogen leaching were significantly lower than rates in sandy loam, and sandy loam peaks are earlier in medium loam. The phenomenon may be due to soil quality and soil clay content resulted in different soil water holding different fertilizer.(3) ammonia volatilization is one of the main ways of nitrogen fertilizer loss. This study, adopting the" closed environment boric acid absorption method", explored slightly water soluble felted and coated fertilizer under different soil moisture condition of ammonia volatilization. The test results show that, under the same soil water content, ammonia volatilization of water soluble felted and coated fertilizer and urea treatment increased first and then reduced. Ammonia volatilization phenomenon of slightly water soluble felted and coated fertilizer was delay of1-3days than ureas, and the time of volatile content reaching a peak lag of4to8days. The accumulated amount of ammonia volatilization of slightly water soluble felted and coated fertilizer was significantly lower than the accumulated amount of ammonia volatilization of urea by31～70mg. Bottle-1, i.e. slightly water soluble felted and coated fertilizer on ammonia volatilization from accumulation to low2.4-5.7points. Thus compared with urea treatment, slightly water soluble felted and coated fertilizer treatments is in greatly reducing the loss of nitrogen fertilizer. In the condition of three different water content, slightly water soluble fertilizer on ammonia volatilization from cumulative amount and soil moisture showed inverse correlation; the higher the water content, the lower cumulative total ammonia volatilization.(4) when water vapor comes into the capsule it will cause the rising of internal pressure and envelope expansion of fertilizer, letting the nitrogen release. This study, adopting the" control of water vapor pressure" method, studies the different water vapor pressure, which water soluble felted and coated fertilizer exposed to, under the condition of nitrogen release. The results show that, under the condition of25DEG℃, in different time slightly water soluble felted and coated fertilizer nitrogen release rate showed a saturated solution of NaCI<KH2PO4<water in saturated solution, water vapor pressure is relatively larger; slightly water soluble fertilizer fertilizer released faster, but rather the contrary. This shows that slightly water soluble felted and coated fertilizers nitrogen release is positively related to water vapor pressure.(5) this study using" pot culture and field crop planting combined test" method, studies the water soluble felted and coated fertilizer under different irrigation conditions, biological effect of nitrogen release. The results show that, the appearance of sparingly water-soluble fertilizer and urea in soil nitrogen emissions increased firstly and then decreased. Compared with urea, slightly water soluble fertilizer release’s cycle is longer, and the release of peak period is later than urea treatment about20days. In crop biomass, plant height stem diameter of chlorophyll index slightly water soluble fertilizer were higher than that of urea. In the nitrogen utilization rate, slightly water soluble urea slow-release fertilizer ratio is higher more than10～24percentage points. In crop yields and its composition, when water soluble fertilizer is in increasing crop grain in N, L, K content, the yields is also higher than the urea1500～3634kg/hm2. It can be concluded that slightly water-soluble slow-releasing fertilizer has significant effect on increasing nitrogen utilization rate, reducing the loss of nitrogen and also contributes to the crop yields. |
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