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Water-repellent soil has a very wide application prospect in the field of agricultural engineering. However, it is still lacking in the hydraulic stability of water-repellent clay. The applications are only targeted at water-repellent dry sand so far. In this study, octadecylamine was taken to modify the highly adsorbent expansive soil with water repellency. A systematic investigation was also conducted to explore the water-repellent and hydraulic stability of loose expansive soil with different water repellency after adsorbing water vapor. Five samples were selected as the compacted expansive soil (hydrophilic expansive soil, hydrophilic expansive soil + hydrophilic sand, hydrophilic expansive soil + water repellent sand, water repellent expansive soil, water repellent expansive soil + water repellent sand). The results show that the greater the humidity was, the greater the mass of water vapor adsorbed by different water repellency expansive soil was. At the same humidity, the water repellency shared little effect on the mass adsorbed by soil. The expansive soil with different water repellency (including slight water repellency) was extremely water repellent after adsorption, where all test points were evenly water repellent. The huge specific surface area of water-repellent expansive soil was obtained for the strong adsorption properties. As such, the water repellency of expansive soil further increased to fully adsorb octadecylamine molecules while adsorbing water vapor during adsorption. After compaction, the water-repellent expansive soil and water-repellent expansive soil + water repellent sand samples exhibited water repellency in a large range of moisture content. There was a range of water-repellent moisture content, all of the soil samples were extremely water-repellent. Compared with the rest, the best hydraulic performance was achieved in the water-repellent expansive soil + water-repellent sand mixed sample share. Specifically, the expansion rate of the expansive soil was reduced from 33.9% to 3.45%, and the shrinkage fissure degree was reduced from 18.75% to 3.6%. Hydrophilic expansive soil realized 90% of the expansion within 90 min, while it took 1 680 min for water-repellent expansive soil and water-repellent sand to complete the same proportion of expansion. Water-repellent modification of expansive soil reduced the expansion amount and rate. There was the basically same air entry value of the hydrophilic sample and the water-repellent sample. But the water content corresponding to the air entry value of the water-repellent sample was smaller than that of the water-repellent sample, and the water-repellent expansive soil matric suction followed the same trend as hydrophilic expansive soil, in terms of moisture content. The pore water pressure remained "negative" at all times in the extremely water-repellent expansive soil, as the moisture content changed. There was no "positive" pore water pressure. There were the lower strength parameters c and φ of water-repellent expansive soil, compared with hydrophilic expansive soil. There was no significant change, indicating better mechanical properties after water-repellent treatment. The special hydraulic properties of waterrepellent expansive soil were attributed to that the water-repellent aggregates remained dry inside the aggregates after immersion. This finding can provide a new idea for the application and promotion of water-repellent clay in agricultural engineering. An experimental basis can be offered to fully expand the application scope of water-repellent soil. [ABSTRACT FROM AUTHOR]

In order to clarify the nutrient utilization characteristics of mechanical dry direct-sowing rice, the objective of this experiment was to study the effects of different mechanical dry direct-sowing modes on absorption, translocation and distribution of nitrogen (N), phosphorus (P), potassium (K), and yield in rice. Two rice cultivars of indica hybrid rice F you 498(143 days growth duration) and conventional japonica rice Xudao 4 (145 days growth duration) were planted with two mechanical dry direct-sowing modes, including no-tillage land and mechanic drilling simultaneously (B1), regulating soil moisture and two rotary tillage before mechanic drilling (B2). Manual broad-cast sowing (B3) was set as control. The dry direct-sowing machine of this study was modified by Nanjing Agricultural University and was re-modified by Sichuan Agricultural University. This machine had 6 drills and sowing depth 2.0 cm, drill spacing 28.0 cm, working width 1.50 m. Motive power of this machine was the Shanghai New Holland tractor (SNH504). This test adopted row spacing 20.0 m × 1.50 m, each plot covered 30 m2 of seeding amount was 30.0 kg per hectare of indica hybrid rice F you 498, 37.5 kg per hectare of conventional japonica rice Xudao 4 respectively. The nitrogen fertilizer amount was 180 kg/hm2. The N application ratios was applied on 4 splits: 50% basal, 30% tillering fertilizer at 3rd leaf stage, 10% panicle N-fertilizer at 4th leaves emerged from the top, 10% ear granular fertilizer at full heading stage. The phosphate fertilizer application was only one base fertilizer. The potash fertilizer application ratio of basic fertilizer, tillering fertilizer and ear granular fertilizer was 2:1:1. The other management measures were at a uniform with high-yield cultivation. The results showed that there was an obvious regulatory effect of rice cultivars and direct-sowing modes on grain yield, absorption and translocation of N, K at the mainly growth stages. There existed significantly positive correlations between the amounts of N, P and K absorption and utilization, which could promote nutrient translocation during filling stage and yield, but the correlation coefficient of P and N, P and K significantly decreased at the mainly growth stages. Under different direct-sowing treatments, the various indicators on yield and nutrient utilization characteristics of F you 498 were significantly higher than those of Xudao 4. Compared with B3 treatment, mechanical direct-seeding treatments under the same variety promoted the accumulations of N, P, and K at the mainly growth stages, increased nutrient translocation in leaf and stem-sheath during filling stage, especially significantly enhanced transportation efficiency of N and K in hybrid rice, and further facilitated translocation conversion rate of N and K in different vegetative organ, played the coupling effect of absorption and utilization of N and K, then to promoted yield, which is the important reason for mechanical direct-sowing rice further to increase yield. Under different mechanical direct-sowing treatments, compared with B1, B2 treatment was the best model in this paper referred as the mechanical direct-sowing treatments, which could further increase nutrient accumulation and translocation from heading to maturity stage in various degrees consequently, promote nutrient accumulation in panicle as well as promote yield. [ABSTRACT FROM AUTHOR]

Biochar is a kind of carbon-rich solid material obtained from biomass resources, which can be used as source of energy, catalyst, adsorbent and soil conditioner. Bamboo is a kind of widely used biomass resource containing high fraction of lignocellulose, and bamboo waste from industrial processing is a kind of good raw material for producing biochars. Hydrothermal carbonization approach was applied at low temperatures to produce bamboo biochars, and the selected biochar samples were further modified by being immersed in the sodium hydroxide (NaOH) solution or calcined in nitrogen atmosphere. The effects of the preparation conditions on the physico-chemical properties of the bamboo biochars were investigated, and the adsorption properties of the biochars for 2-naphthol and Congo red from their aqueous solutions were evaluated. The results showed that the yields of the bamboo biochars from hydrothermal carbonization without modification were between 54.12% and 71.53%, and the functional groups containing oxygen such as -OH (3 200-3 600 cm-1), C=O (1 650-1 735 cm-1) and C-O (1 000-1 250 cm-1) were found to be rich on the surfaces of these biochars; the oxygen content of the bamboo biochar produced at 200 ℃ and 7 h was as high as 46.33%, and the surface area of the same carbon sample was measured to be 14.10 m2/g. The bamboo biochars modified by being immersed in the NaOH solution still showed rich oxygen-containing groups on their surfaces, high yields were also achieved with these samples, much larger surface area (33.22 m2/g) was obtained for the biochar sample produced at 200 ℃ and 7 h and modified by soaking in NaOH solution for 1 h, and the oxygen content of this carbon sample was 50.57%, which was higher than that of the sample before modification treatment. On the other hand, few functional groups were found on the surfaces of the bamboo biochars modified by calcination in nitrogen atmosphere, the yields of these biochar samples were much lower (between 12.99% and 16.21%), even higher surface area (52.39 m2/g) was observed for the biochar sample produced at 200 ℃ and 7 h and modified by calcining in nitrogen atmosphere at 700 ℃, the carbon content of this carbon sample was 75.87%, and the oxygen content of this sample decreased to 20.89%. All of the bamboo biochar samples without modification treatment could adsorb 2-naphthol and congo red from aqueous solutions, of which the sample produced at 160 ℃ and 3 h showed the largest adsorption capacity for 2-naphthol (50.3 mg/mL at 25 ℃, initial concentration of 0.5 mg/mL), and the sample produced at 200 ℃ and 7 h showed the largest adsorption capacity for Congo red (63.7 mg/mL at 25 ℃, initial concentration of 0.5 mg/mL), and these 2 kinds of bamboo biochar samples were chosen as the most promising adsorbents for the adsorptive removal of 2-naphthol and Congo red. Surface adsorption was inferred to be the predominant mechanism for the adsorption of Congo red on the surfaces of the bamboo biochars, while a complex mechanism involving partition was suggested for the adsorption of 2-naphthol on the biochars. The NaOH immersion method was favorable for obtaining biochars with higher adsorption capacities for both 2-naphthol and Congo red, and the bamboo biochar sample produced at 200 ℃ and 7 h and modified by soaking in NaOH solution for 1 h displayed the largest adsorption capacities for both 2-naphthol (62.3 mg/mL at 25 ℃, equilibrium concentration of 0.3 mg/mL) and Congo red (69.1 mg/mL at 25 ℃, equilibrium concentration of 0.3 mg/mL). However, calcination in nitrogen didn't show positive effects on the adsorption properties of the bamboo biochars especially for the adsorption of 2-naphthol. The results obtained show that bamboo biochars produced through hydrothermal carbonization can be applied as low cost adsorbents for adsorptive removal of 2-naphthol and Congo red from wastewater. [ABSTRACT FROM AUTHOR]

Retrograded corn amylose is a kind of resistant starch which is formed by the interaction of amyloses through hydrogen bonds. Those bonds hinder the combination of starch and water/amylase, which makes retrograded amylose insoluble and resists amylase hydrolysis. Some of retrograded corn amyloses can form regular crystal with identical characteristic named B-type structure. Such crystal structure provides possibility to absorb organic compounds containing hydroxyls. There are residual carbohydrates, amino acids, water soluble protein and peptides and so on in fermentation broth in the production of monascus red pigments by fermentation liquid method. It is difficult to isolate those substances from pigments in the following process, so the pigments are mixed with impurities in the product. These impurities reduce the degree of pigment purity and bring uncertainties to the stability of pigments in use. The retrograded starch is insoluble in water and contains a lot of hydroxyls, so hydrogen bond can form between starch and hydroxyl-containing pigments or other organic compounds containing a large number of hydroxyl groups. Then the substance containing a lot of hydroxyls is absorbed by retrograded starch, but those ones having no or fewer hydroxyls will stay in solutions. Thus, the component containing hydroxyl groups will be separated from solutions. In this paper, the corn amyloses with different molecular weight distributions were made by retrogradation method and those amyloses were used to absorb monascus red pigments. Absorption capacity and speed of monascus red pigments by those amyloses were determined. The results showed that the maximum absorption capacities of monascus red pigments by amyloses retrograded for 1-4 times were 0.56, 0.84, 1.04, and 1.10 mg/g respectively, when the absorption temperature was 80℃ and the absorption time was 140 h. The narrower the molecular weight distribution of amylose and the higher the absorption temperature, the higher the absorption speed. The average absorption free energies of all samples, which were calculated by Dubinin-Radushkevich adsorption isotherm equation, were less than 8 J/g. Such calculated results suggested that the pattern for retrograded corn amylose to absorb monascus red pigment belonged to physical absorption. The results of the scanning electron microscope (SEM) indicated after drying those retrograded corn amyloses presented some kinds of more bouffant structure when they were combined with monascus red pigments. In order to increase the pigment absorption content of retrograded corn amylose, the regular crystal should be cultured from amylose with the narrowest distribution of molecular weight. So the method of preparing those materials became vital. Only identical amylose with special chain length could involve in retrograded amylose, so amylose with narrow distribution of molecular weight could be obtained by repeated retrogradation. The results of the paper provide a reference for isolating and purifying monascus red pigments with hydroxyls. [ABSTRACT FROM AUTHOR]

The straw-bale has been widely used in the building field, compared to the traditional architecture material, it has lots of advantages such as high thermal resistance value, light weight, and environmental friendly material. In order to investigate the application effect, a solar greenhouse was designed and built with straw-bale. The performance of straw-bale wall solar greenhouse was evaluated, and compared with the soil wall and brick wall solar greenhouse. The hygroscopicity and desorption of straw, and thermal conductivity of straw-bale were evaluated. The moisture content of straw-bale, temperature and humidity, crop yield, morbidity of different solar greenhouse (soil wall, brick wall, and straw-bale wall) were discussed in the paper. The results showed that the maximum moisture content of straw was about 22.0% under the condition of 97% relative humidity and 25°C temperature, while the maximum moisture content of straw in the solar greenhouse was 23.6% during the experiment. The thermal conductivity of straw-bale with density of 0.20 g/cm3 was 0.069 W/(m·K), while the thermal conductivity of soil wall and brick wall were 1.210 W/(m·K) and 0.982 W/(m·K). The inertia index of straw-bale wall (0.46 m), soil wall (4.0 m) and brick wall (0.5 m) were 5.603, 43.513, and 4.636, respectively. The air temperature in the straw-bale wall solar greenhouse was 1.3°C higher than that in the brick wall solar greenhouse, and 2.1°C lower than that in the soil wall solar greenhouse. All the air temperature of solar greenhouse was above 9.0°C when the outdoor temperature was -7°C. The soil temperature in the straw-bale wall solar greenhouse was 1.2°C higher than that in the brick wall solar greenhouse, and 1.1°C lower than that in the soil wall solar greenhouse. All the soil temperature of solar greenhouse was above 12.1°C when the outdoor temperature was -7°C. The average air relative humidity of straw-bale wall, soil wall, and brick wall solar greenhouse were 75%, 87%, and 84%, respectively. The straw-bale displayed the adjusting capacity at some extent for the greenhouse air humidity due to the structural porosity of straw. It can not only improve the internal environment of greenhouse, but also restrain the occurrence of plant diseases. During full fruit period of the planted color peppers, the morbidity in the greenhouse with soil wall, brick wall, and straw-bale wall were 25%, 50% and 0, respectively, and the crop yields in the three kinds of greenhouse were 6 375, 7 130 and 6 833 kg, respectively. What's more, according to the design in the work, 35 000 kg straw (air dried) had been used to build the straw-bale wall solar greenhouse in this study. Also, the utilization rate of the land can improve by 34.6% due to reducing the wall thickness. In a conclusion, the straw bale has the potential to replace the soil or brick wall for building solar greenhouse thermal insulation wall. Further research should be paid attention on optimization of the straw greenhouse structural design, for example, the wall base and outer surface structural improvement, so as to elevate the thermal performance of straw bale greenhouse. [ABSTRACT FROM AUTHOR]