Manipulation of composting oxygen supply to facilitate dissolved organic matter (DOM) accumulation which can enhance maize growth.

Promotion of crop yield by compost application is generally thought to be ascribed to a better supply of macro and micronutrients, however the importance of compost DOM on plant growth has not been well demonstrated. In this study, composting of chicken manure, spent mushroom and sawdust was conducted under aerobic or anaerobic condition to determine the effects of compost DOM on plant growth. It was found that dissolved organic matter (DOM) first increased and then decreased in compost, and DOM of anaerobic compost was slightly higher than that of aerobic compost. When compost extract was applied to maize, among N, P, K and DOM content, it was DOM content that was most significantly and strongly related to plant biomass (r = 0.843, p＜0.001). Compost DOM was also strongly related to soil properties, the improvement of which can also promote plant growth. Compost application confirmed that higher compost DOM results in greater plant biomass. In order to facilitate compost DOM accumulation, we designed a novel composting process which combined aerobic and anaerobic treatments, and the resulting compost (A-Ana compost) with the highest amount of DOM displayed the best performance in promotion of plant growth. A-Ana compost was able to increase maize biomass by 32.71% and 12.40% compared with only anaerobic or aerobic compost, respectively. Therefore, DOM is a critical factor determining compost quality and it is feasible to manipulate composting oxygen supply condition to increase compost DOM, which will lead to increased plant yield.

Characteristics and mechanisms of acrylate polymer damage to maize seedlings.

Superabsorbent acrylate polymers (SAPs) have been widely used to maintain soil moisture in agricultural management, but they may cause damage to plants, and the mechanisms are not well understood. In this study, seed germination, soil pot culture, hydroponic experiments, and SAPs degradation were conducted to investigate damage characteristics and mechanisms associated with SAPs application. The Results showed that SAPs inhibited maize growth and altered root morphology (irregular and loose arrangement of cells and breakage of cortex parenchyma), and the inhibitory effects were enhanced at higher SAPs rates. After 1h SAP hydrogels treatment, root malondialdehyde (MDA) content was significantly increased, while superoxide dismutase (SOD) and catalase (CAT) content were significantly decreased. Hydroponics experiment indicated that root and shoot growth was inhibited at 2.5mgL(-1) acrylic acid (AA), and the inhibition was enhanced with increasing AA rates. This effect was exacerbated by the presence of Na(+) at a high concentration in the hydrogels. Release and degradation of AA were enhanced at higher soil moisture levels. A complete degradation of AA occurred between 15 and 20 days after incubation (DAI), but it took longer for Na(+) concentration to decrease to a safe level. These results indicate that high concentration of both AA and Na(+) present in the SAPs inhibits plant growth. The finding of this study may provide a guideline for appropriate application of SAPs in agriculture.

Starch derivative-based superabsorbent with integration of water-retaining and controlled-release fertilizers.

Phosphate rock (PHR), a traditional fertilizer, is abundant, but is hard to be utilized by plants. To improve the utilization of PHR, and to integrate water-retaining and controlled-release fertilizers, an agricultural superabsorbent polymer based on sulfonated corn starch/poly (acrylic acid) embedding phosphate rock (SCS/PAA/PHR) was prepared. PHR can be suspended and well-dispersed in SCS/PAA by sulfonated corn starch (SCS). PHR and KOH were mixed in acrylic acid solution to provide phosphorus (P) and potassium (K) nutrients, respectively. Impacts on water absorption capacity of the superabsorbent were investigated. The maximum swelling capacity in distilled water or 0.9 wt.% (weight percent) NaCl solution reached 498 g g(-1) and 65 g g(-1) (water/prepared dry superabsorbent) respectively. Moreover, release behaviours of P and K in SCS/PAA/PHR were also investigated. The results showed that SCS/PAA/PHR possessed excellent sustained-release property of plant nutrient, and the SCS/PAA could improve the P release greatly. Besides, the XPS analysis was employed to study the relationship between PHR and superabsorbent polymer.

[Effects of urea and coated urea on harmful gases concentrations in plastic greenhouse].

With simulation test and plastic greenhouse experiment, this paper studied the effects of urea and minerals- coated urea on the soil pH and harmful gases concentrations in plastic greenhouse. The results showed that under simulated condition, the application of these'two N fertilizers led to an initial increase of soil pH, which reached the maximum (an increment of > 50%) within the first week and dropped to the initial level by the end of the fifth week. In plastic greenhouse, applying urea and coated urea resulted in the increase of NH3, NO2 and O3 concentrations. The daily volatilization amount of NH3 and NO2 was higher in urea treatment than in coated urea treatment, and the highest value in urea treatment was 42.36 microg x m(-3) x d(-1) for NH3, 41.95 microg x m(-3) x d(-1) for NO2, and 86.00 microg x m(-3) x d(-1) for O3. The volatilization intensity of NH3 and NO2 was influenced by temperature and sunlight, while the O3 concentration was influenced by sunlight.

Controlled-release fertilizer (CRF): a green fertilizer for controlling non-point contamination in agriculture.

Fertilizers contribute greatly to high yields but also result in environmental non-point contamination, including the emission of greenhouse gas (N2O) and eutrophication of water bodies. How to solve this problem has become a serious challenge, especially for China as its high ecological pressure. Controlled-release fertilizer(CRF) has been developed to minimize the contamination while keeping high yield and has become a green fertilizer for agriculture. Several CRFs made with special coating technology were used for testing the fertilizer effects in yield and environment through pot experiment and field trial. The result indicated that the CRFs had higher N use efficiency, thus reducing N loss through leaching and volatilization while keeping higher yields. Comparing with imported standard CRFs, the test on CRFs showed similar fertilizer effect but with much lower cost. CRFs application is becoming a new approach for minimizing non-point contamination in agriculture.

Study on structural characteristics of pillared clay modified phosphate fertilizers and its increase efficiency mechanism.

Three types of new high-efficiency phosphate fertilizers were made when pillared clays at certain proportions were added into ground phosphate rock. Chemical analyses showed that their soluble phosphorus content decreased more than that of superphosphate. Pot experiment showed that, under equal weights, the new fertilizers increased their efficiency by a large margin over that of superphosphate. Researches on their structures by means of XRD, IR and EPR spectrum revealed that their crystal structures changed considerably, improving their activity and preventing the fixation of available phosphorus in the soil, and consequently, greatly improved the bioavailability and became the main cause of the increase of biomass.

[Biological availability of zinc lignosulfonate on calcareous soil of north Guoangdong Province].

Zinc lignosulfonate (Zn-LS) is a kind of organic fertilizers made from the by-products of paper industry. With leach and plot treatments, this paper studied the difference of the biological availability between Zn-LS and an inorganic Zn-fertilizer on calcareous soil of north Guangdong Province. The results indicated that the Zn of Zn-LS was less absorbed by calcareous soil. In soil B, when applying 10 mg x kg(-1) Zn, the dissolved amount of Zn-LS was 65.2% higher than that of inorganic Zn-fertilizer, corn grew well, and its biomass was higher. In soil A, when applying 10 mg x kg(-1) Zn of Zn-LS, the biomass of corn increased by 16.3%, and its Zn content was 81.2% higher. Therefore, biological availability of Zn-LS was better than that of inorganic Zn fertilizer.

[Effects of different organic materials and their composting levels on soil microbial community].

In this paper, a pot experiment with tomato and different organic material amendment was installed in a greenhouse, and the diversity of soil microbial communities and their utilization pattern of amine, amino acid, carbohydrate, carboxylic acid, polymer and miscellaneous were assessed by Biolog method at 60 days after amendment. The results showed that organic material amendment could improve soil microbial community diversity. Fresh distiller grain amendment was a little bit better than its 10 days composting, and the composting level of cow manure had a significant positive or negative effect on the microbial diversity. Among the six carbon sources, the utilization of carbohydrate by soil microbial communities was the highest, and the microbial communities in soils amended with distiller grain had a significantly higher utilization of polymer, relative to those in soils amended with cow manure.

[Mitigation effect of several controlled-release N fertilizers on ammonia volatilization and related affecting factors].

By using static absorption and soil column leaching methods, this paper studied the behaviors of several controlled-release N fertilizers in soil under laboratory conditions. The results showed that under the application rate of 450 mg x kg(-1), total ammonia volatilization from three controlled-release fertilizers decreased by 49.7%, 28.0% and 71.2%, respectively, in comparing with common urea. When the application rate was 600 mg x kg(-1), total ammonia volatilization decreased by 34.6%, 12.3%, 69.9%, respectively. Controlled-release fertilizers could markedly reduce total ammonia volatilization from soil and decrease environment pollution via fertilization. The results also indicated that total ammonia volatilization correlated significantly with soil urease activity, pH value and N leaching rate. The correlation coefficient between total ammonia volatilization and accumulated N leaching rate was 0.9533, and that between total ammonia volatilization and soil urease activity and pH value was 0.9533 and 0.9908, respectively.

[Decomposing effect of chemical-biological decomposing combined technique on rice straw and its fourier transform infrared spectroscopy].

The effects of several chemical-biological combined decomposing techniques (CBCDT) on the decomposition of rice straw were studied by fourier transform infrared spectroscopy (FTIR). The results showed that under CBCDT treatments, rice straw could be better decomposed than in control. After seven days under CBCDT treatments, the straw turned into brown, and was easy to be broken down and obviously decomposed. FTIR spectra indicated that under chemical agent A-biological agent A combined treatment, hydroxyl, ketonic carbonyl, methyl, methylene, methane and aliphatic compounds decreased, proteins and amino acids completely decomposed, but aromatic compounds (specially substituted group) increased, and hence, the humification of straw was accelerated. The effects of different decomposing agents on straw were decreased in the order of chemical degrade agent A > chemical degrade agent B, biological degrade agent A > biological degrade agent B > biological degrade agent C. The chemical agent A-biological agent A combined treatment was the most effective among several treatments.

[Effect of ecological organic fertilizer on tomato bacterial wilt and soil microbial diversities].

The effects of ecological organic fertilizer (EOF) on tomato bacterial wilt and soil microbial community were studied through field trial and fatty acid methyl esters (FAMEs) analysis. The results showed that the incidence rate of tomato bacterial wilt was 100% in continuous cropped soil, and significantly reduced to 39% and 50% when applying EOF at 1.0 kg.m-2 and 0.5 kg.m-2, respectively. There was no significant difference between two fertilization treatments. The fatty acid fingerprints of soil microbial community were greatly changed, and the relative contents of cyc17:0 cited as biomarker for GN bacteria, c18:2 w6 as biomarker for fungi and c16:1 11c as biomarker for arbuscular mycorrhizal (AM) fungi all increased when applying EOF. The minimum distance of cluster analysis was 1.08 between control and treatments of applying ecological organic fertilizer, and 0.70 between different fertilization treatments. Applying EOF could adjust soil microbial community structure, benefit for soil beneficial microbes, and develop stability and disease suppression of soil ecological system, and hence, improve soil quality.

[Effect of lignosulfonates on controlling of urea nitrogen transformation and nitrate accumulation in vegetable].

Indoor cultivation experiment and plot field experiment were conducted to study the effect of lignosulfonates on urea nitrogen transformation in soil and the mechanism of controlling nitrate pollution in vegetable. Results showed that lignosulfonates behaved inhibition effect on urea hydrolysis compared with the contrast treatment, the contents of remainder urea nitrogen treated with lignosulfonates was more than that of another kind of urease inhibitor hydroquinone in soil after 69 hours' cultivation. Lignosulfonates could reduce contents of nitrate in cabbage, it as well increase contents of vitamin C in a large degree, enhance the nitrate reductase activity, then accelerated nitrogen assimilation in plants. The urease activity was lower and contents of ammonium nitrogen in soil was larger after ingathering, lignosulfonates could keep nitrogen release slowly, and could be used as a kind of effective inhibitor to nitrogen fertilizer in the controlled-release fertilizers.