Preparation Of Attapulgite Coated Slow-release Fertilizer And Its Effects On Crop Productivity In A Rain-fed Cropland

In many semiarid areas of China, crop production is often limited by poor soil fertility and low fertilizer use efficiency. The low-cost slow-release fertilizers may play an important role in improving the productivity of field crops and reducing environmental risks. However, no slow-release fertilizers are suited for maize in semiarid area of China so far. With the aim of improving fertilizer use efficiency and minimizing negative impacts on the environment, a new attapulgite-coated slow-release fertilizer was prepared. Attapulgite is a natural clay mineral which has slow releasing character, rich reserves and low price. The objective of current research was to assess if attapulgite-coated fertilizers can be used as slow-release fertilizers for maize or potato in a typical semiarid area. According to the method of formula fertilization by soil testing and the nutrient demand of maize or potato in its three main growth stages, attapulgite-coated fertilizers were prepared by dividing chemical fertilizers into three parts and coating each part with a layer of attapulgite. This design was novel and unique, satisfying the demands of maize throughout the whole growing season with the slow release of nutrients from the coated layers. A field experiment was conducted in2010and2011. In2010, four types of fertilizers were compared:20%attapulgite-coated chemical fertilizer (A20CF),30%attapulgite-coated chemical fertilizer (A30CF),20%attapulgite mixed chemical fertilizer (A20MF), and chemical fertilizer only (CK). While in2011, three types of fertilizers were compared:30%attapulgite-coated chemical fertilizer (A30CF),30%attapulgite mixed chemical fertilizer (A30MF), and chemical fertilizer only (CK).There were three fertilizer rates for maize (all kg ha-1):(1)94.22N and22.49P,(2)139.09N and38.98P, and (3)254.23N and50.98P; and three fertilizer rates for potato (all kg ha-1):(1)94.5N and4.5P,(2)137.9N,16.5P and10.5K, and (3)223.4N,24.0P and81.0K. Two side field experiments without plants were run in2011to determine the release behavior of different fertilizers. A30CF, A30MF and CK for maize and potato were tested. Fertilizer rates were set as139.09kg N ha-1and38.98kg P ha-1and37.9N,16.5P and10.5K, respectively.The results of side field experiments without plants showed that during60-120d after fertilization, the increase of soil mineral N and available P in the ACF treatment were significantly lower than in the CK and AMF treatments. That means ACF had a slow release effect which release nutrients slower than CK and AMF treatments. ACF could satisfied the demands of crop throughout the whole growing season while the conventional fertilizer had released most of its nutrients early in the season.The results of potato leaf NO3--N showed that an increase of leaf NO3--N concentration appeared with ACF treatments from100d after the application of fertilizers, while the concentration with CK and AMF maintained a decrease trend. That further demonstrated the slow release effect of ACF which could continually provide N to potato during the later growing season.The results of field experiments with maize showed that grain yield with ACF treatment was significantly higher than CK and AMF treatment, A30CF had the best performance. In2010, A20CF increased the grain yield by12-19.7% when compared with CK and10.7-19.2% when compared with A20MF respectively, A30CF increased the grain yield by19.5-26.7% when compared with CK and17.5-26.2% when compared with A20MF respectively; In2011, A30CF increased the grain yield by9-11%when compared with CK and5.7-8.2%when compared with A30MF respectively. Increased grain yield with ACF was largely due to increased grain numbers per ear and100-kernel weight. The use of ACF also improved aboveground biomass, water use efficiency and partial factor productivity of N and P fertilizer. Soil mineral N content after harvest with ACF treatments was also significantly improved in both years.The results of field experiments with potato showed that total tuber yield and marketable tuber yield with ACF treatment was significantly higher than CK and AMF treatment, A30CF had the best performance. In2010, for total tuber yield, A20CF increased by13.3-19.7%when compared with CK and11.1-17.5%when compared with A20MF respectively, A30CF increased by18.6-25.8%when compared with CK and16.3-23.5%when compared with A20MF respectively; for marketable tuber yield, A20CF increased by19.1-28.9%when compared with CK and14.7-24.4%when compared with A20MF respectively, A30CF increased by25.4-39.6%when compared with CK and20.8-34.8%when compared with A20MF respectively. In2011, for total tuber yield, A30CF increased by10.6-14.7%when compared with CK and9-14.5%when compared with A30MF respectively; for marketable tuber yield, A30CF increased by15.0-20.6%when compared with CK and12.9-17.8%when compared with A30MF respectively. Increased tuber yield with ACF was largely due to increased mean tuber weight and plant yield. The use of ACF also improved aboveground biomass, water use efficiency and partial factor productivity of N, P and K fertilizer. Soil mineral N content after harvest with ACF treatments was also significantly improved in both years.For the good performance on improving yield, fertilizer use efficiency and water use efficiency of maize and potato, easy to prepare, and being economical and eco-friendly, the attapulgite coated fertilizers could find good application in crop production of rain-fed areas and be beneficial to agricultural sustainability.