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The long‐term effects of controlled‐release urea (CRU) on crop yields and soil properties were investigated in lysimeters under wheat and corn rotation system from 2009 to 2014 in northern China. The CRU included polymer‐coated urea (PCU), sulfur‐coated urea (SCU), and polymer coating of sulfur‐coated urea (PSCU) was applied at 147, 210 kg N ha−1 for wheat and 262.5, 375 kg N ha−1 for corn and the urea was applied at 210 kg N ha−1 for wheat and 375 kg N ha−1 for corn. Results showed that the N release characteristics of three kinds of CRU in field condition were all closely matched to the N requirement of crops. Consequently, the CRU treatments improved wheat and corn yields by 3.2 to 10.1% and 4.9 to 11.1%, increased apparent N use efficiency by 45.9 to 53.8% in wheat, and 36.2 to 45.4% in corn, respectively, compared with urea. Furthermore, the PSCU achieved the highest and the most stable crop yields among CRU. Even reducing CRU rate by 30% produced the same yields as with the 100% rate of urea. In addition, soil total N and organic matter contents in CRU were effectively increased in the topsoil of 0 to 20 cm after 5 yr. Therefore, long‐term application of CRU had great potential to increase wheat–corn yields, N use efficiency, reduce application frequency, improve soil fertility, decrease the leaching of soil NO3−–N and NH4+–N, and also relieve soil pH decreased.Core Ideas The long‐term effect of controlled‐release urea on crop yield and soil chemical properties was studied. The N release rates of controlled‐release urea were closely matched to the demand for N during the whole growth periods of crops. The wheat and corn yields were increased by 3.2 to 10.1% and 4.9 to 11.1% by controlled‐release urea fertilization, compared with urea treatment.

Biochar application as a soil amendment has been proposed as a strategy to improve soil fertility and increase crop yields. However, the effects of successive biochar applications on cotton yields and nutrient distribution in soil are not well documented. A three-year field study was conducted to investigate the effects of successive biochar applications at different rates on cotton yield and on the soil nutrient distribution in the 0–100 cm soil profile. Biochar was applied at 0, 5, 10, and 20 t ha-1 (expressed as Control, BC5, BC10, and BC20, respectively) for each cotton season, with identical doses of chemical fertilizers. Biochar enhanced the cotton lint yield by 8.0–15.8%, 9.3–13.9%, and 9.2–21.9% in 2013, 2014, and 2015, respectively, and high levels of biochar application achieved high cotton yields each year. Leaching of soil nitrate was reduced, while the pH values, soil organic carbon, total nitrogen (N), and available K content of the 0–20 cm soil layer were increased in 2014 and 2015. However, the changes in the soil available P content were less substantial. This study suggests that successive biochar amendments have the potential to enhance cotton productivity and soil fertility while reducing nitrate leaching.

Nitrogen fertilizer is important for improving wheat (Triticum aestivum L.) and corn (Zea mays L.) yields, but inappropriate application methods and excessive amounts lead to low N use efficiency and high N losses through leaching. To investigate the effects of controlled‐release urea (CRU) on crop yield and soil fertility, a field experiment was conducted from 2012 to 2014 in China. The 100% (180 kg ha−1) and 70% (126 kg ha−1) of the local practice N rates with CRU and urea were used. The results revealed that the release curves of CRU in the natural field corresponded well to the N requirements of wheat and corn plants, and a positive linear correlation was observed between release rates and days after buried in soil. Consequently, the CRU treatments achieved significantly higher wheat and corn yield by 8 to 12% and 9 to 11%, respectively, compared with urea treatments at the same N rate. Reducing N rate of CRU by 30% produced the same yield as with the 100% N rate of urea. The agronomic nitrogen use efficiency (NUE) was significantly increased and the leaching of soil N was reduced by CRU. The acidification rates and leaching of exchangeable Ca2+, K+, Na+ contents were reduced, base saturation and available P improved by application of CRU compared with urea. Therefore, the results suggested that a 30% decrease of CRU in the recommended application rate of N, can be an effective measure to save consumption input of N fertilizer.Core Ideas Nitrogen release rates of controlled‐release urea in field condition corresponded well to the N uptake of crop plants. A 30% decrease in the application rate of N is possible with controlled‐release urea compared to urea. The application of controlled‐release urea increased crop yield, N use efficiency, net farm profit, and soil fertility.

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Due to considerable application of perfluorooctanoic acid (PFOA) and its refractory degradation, the widespread distribution of PFOA has already resulted in its' risks to environment and organisms. However, the intrinsic characteristic of pristine multi-walled carbon nanotubes (MWCNTs) limited their application for removing PFOA from aqueous medium. Therefore, three nano-metals (nano-crystalline iron, copper and zinc) grafted MWCNTs were synthesized and characterized by BET-N, TEM, FTIR, XPS and XRD as well as MWCNTs (as the control treatment) in this study. The results showed that nano metals were well grafted on the surface of MWCNTs. Adsorption were investigated by using radioactive labeled PFOA (C-PFOA) to quantify the trace PFOA. Adsorption kinetics showed the adsorption of PFOA on the metal doped MWCNTs (MDCNTs) was controlled by intra-particle diffusion. Adsorption isotherms showed the sorption amounts on the MDCNTs were higher than the control. This attributed much to the hydrophobic interaction, electrostatic interaction and the formation of the inner sphere complexes. Ionic strength (0-100 mM) and ionic species (Ca) had little effects on the sorption of MDCNTs. PFOA adsorption on MDCNTs strongly depended on pH value in the medium. These results provide an innovative approach for removing trace PFOA from liquid medium.

Potassium (K) is one of the major mineral elements required for normal growth of cotton. However, understanding the effect of controlled‐release K fertilizer on leaf photosynthesis and K use efficiency (KUE) of cotton is currently limited. A two‐year pot experiment was consecutively conducted in 2014 and 2015 with three kinds of K fertilizer including K2SO4, KCl, and polymer‐coated KCl (CRK), each at four application rates (0.00, 0.86, 1.73, and 2.59 g K plant−1, respectively). For each type of K fertilizer, the yield and K uptake of cotton increased but the KUE decreased with higher K fertilizer application. The release characteristics of K from CRK corresponded well to the K requirements during cotton growth. Plant‐available soil K, as well as leaf SPAD values, net photosynthetic rate (Pn), maximal photochemical efficiency (Fv/Fm), and effective quantum yield of photosystem II (ΦPSII) in CRK treatments were increased after full bloom stage compared to conventional K fertilizers under the same potassium application rate. Consequently, the CRK treatments significantly increased lint cotton yields by 8.1–32.7% and 3.7–20.8%, while the KUE increased by 15.5–54.8% and 14.5–45.4% compared to KCl and K2SO4 treatments, respectively. The results indicate that the application of CRK is intensively recommended to replace conventional potassium fertilizers for gaining greater yields and higher KUE of cotton.

Few studies have paid attention to high-concentration controlled release potassium (CRK) fertilizer because conventional potassium chloride (KCl) particles with the characteristics of irregular, high specific surface area, and bad fluidity are generally unsuitable to produce controlled-release fertilizer. The objective of this study was to investigate the interacting effects of urea-formaldehyde and additives on KCl granulation. In addition, the controlled-release characteristics of CRK based on modified KCl particles were determined in our research. Results indicated that 4–8% urea-formaldehyde combined with 6–8% bentonite was used as a double binder to increase the granulation rate, smoothness, and particle hardness of KCl granules, which enhanced its characteristics for the coating process. The K release rates of modified KCl particle-based CRK were significantly lower than that of the conventional KCl particle. In conclusion, the novel KCl granulation technology has an enormous potential for large-scale applications to satisfy the increasing demand for CRK fertilizers in the future.