Effects Of Different Blending Proportions And Soil Water Suction On Nutrient Release Characteristics Of Controlled Release Urea

The release characteristics after blend were affected by the influence of different blending ratio of controlled release urea with different release longevities. Based on the controlled release fertilizer industry standard(HG/T 4215-2011), three kinds of controlled release urea were tested with 25? still water extraction and Kjeldahl determination,and 100? water fast extraction methods in this study. The experiment was carried out to investigate the effects of different blending ratios of controlled release urea on nutrient release characteristics.Different soil water suction said the effectiveness of the soil moisture in the form of water energy. Under the condition of different soil water content, soil porosity of air relative humidity can be expressed in the water vapor saturation. The experiment was carried out to investigate the effects of different soil water suctions on controlled release fertilizer. Six different water treatments were set up in the experiment: ADS(air dried soil); SWS525; SWS80; SWS55; SWS30 and SWS0(SWS means soil water suction). Simulation experiment was carried out in the constant temperature box by setting the same treatment in soil water suction as the pots at the same time. The controlled release fertilizer would be packaged and embedded in soil, sampled and tested on a regular time.The main results were as follows:1. The nutrient release rate of measured value was similar to the calculated value by using weighted value of different blending ratios of controlled release urea. The release periods of bulk-blending controlled release urea were the same as the longger controlled release urea, nutrient release peak points were in associated with the blending ratios of controlled release urea.2. In the constant temperature simulation experiment, the release longevities of CRU were generally similar, the air relative humidity in soil pores were over 95%, and the soil vapor were saturated with water in the treatments of 75 kPa, 30 kPa and 0 kPa soil water suction, which indicated that soil water conditions were no longer the main factor that influenced the release rate of CRU. The release longevities were 416.4 d and 120.0 d, respectively, in 525 kPa and 260 kPa soil water suction treatments, in which the air relative humidity in soil pores were 84% and 91%, respectively. The relative differences were 146.8% and 59.1% compared with the soil saturated water release longevity(63.6 days), which were more than the value(20%) allowed by the controlled-release fertilizer industry standards, which showed that release rate and release longevities of CRU were restrained by high soil water suction.3. In the potted experiment, whether with or without planted ryegrass, the release longevities of CRU were generally similar at same soil water suction. The results in both the simulation experiment and potted experiment were basically identical, but the release longevities of CRU in simulation experiment were slightly longer than that in the potted experiment, because of the average temperature during the potted experiment(21?) was lower than that in constant temperature simulated experiment.