纳米生物炭对铵态氮的吸附-解吸效果研究

为研究纳米生物炭对铵态氮的吸附-解吸效果,以稻草秸秆为原料制得本体生物炭,并采用球磨法制备纳米生物炭,通过室内吸附-解吸试验与模型模拟相结合的方法开展研究。结果表明：相对于本体生物炭,纳米生物炭对铵态氮的吸附-解吸效果均表现出极显著的优势。纳米生物炭对铵态氮的吸附量随其投加量和初始溶液氮浓度的增大呈增加趋势,随后趋于平衡;其在pH为7的条件下对铵态氮的吸附效果最好;吸附时间为210 min时,吸附反应达到动态平衡。纳米生物炭对铵态氮的最大吸附量为6.91 mg/g,是相同条件下本体生物炭吸附量的2倍。纳米生物炭对铵态氮的吸附等温线和吸附动力学过程更适合用Langmuir方程和准二级动力学方程描述。纳米生物炭在解吸时间为240 min时,解吸反应达到动态平衡。纳米生物炭最大解吸量为6.051 mg/g,是相同条件下本体生物炭解吸量的1.9倍。准二级动力学方程能更好地描述纳米生物炭对铵态氮的动态解吸过程。纳米生物炭对铵态氮的吸附主要为单分子层吸附,以化学吸附方式为主,解吸过程可以看作是吸附反应的逆向过程。研究结果可为田间施用纳米生物炭减少氮素流失、提高氮肥利用率提供理论依据。     

水肥耦合对南瓜生长及产量的影响研究进展

传统的灌水、施肥方式不仅水肥利用率低、浪费人工和成本,而且污染农田环境。水肥耦合技术通过对灌水与施肥合理的配比来达到提高水肥利用效率、产量、品质及降低生产成本的目的。本文主要综述了水肥耦合调控对南瓜的生长发育过程、光合作用、产量及品质的影响。结果表明,合理的水肥调控能显著促进南瓜生长发育及光合作用,对干物质积累有积极作用,提高了南瓜的产量与品质。最后对水肥耦合技术在农业生产中的推广与应用进行了展望。     

Particle-size effects on soil temperature, evaporation, water use efficiency and watermelon yield in fields mulched with gravel and sand in semi-arid Loess Plateau of northwest China

Gravel and sand mulch is an effective practice in conserving soil and moisture. However, the proportion of different particle size in this kind of mulch layer is an important factor to be considered in order to obtain optimal results from this practice. From 2005 to 2007, a series of experiments including one with watermelon were conducted in the semi-arid Loess Plateau of northwest China to determine the influence of particle size and its proportion in mulch layer on soil temperature, evapotranspiration, water use efficiency (WUE) and watermelon (Citrullus lanatus L.) yield. The treatments in no-watermelon experiments included particle sizes classified as <0.3, 0.3-1, 1-2, 2-4, 4-6, 6-8 and 8-10 cm mesh size or various rates of 2-6 cm pebble accounting for 0, 10, 20, 30, 40, 50, 60 and 70% with 30% 1-2 cm gravel-sand in mulch layer (as well as correspondingly decreasing sand proportions). The watermelon experiment included three particle sizes, 0.3-1, 1-2 and 2-6 cm. Soil temperature at 8:00 h was highest for the 1-2 cm treatment, and the daily average temperature at 14:00 h was highest for the 0.3-1 cm treatment. Soil temperature decreased with particle size increasing due to porosity enlarging. The relationship between soil temperature and particle size followed a quadratic or cubic curve. Soil temperature was increased by gravel-sand mulch plus plastic film. The increment of soil temperature was larger especially for 1-4 cm particle size. In the gravel-sand mulch layer having different size particles, the greater percentage being of 2-6 cm pebbles, increases porosity, and lowers soil temperature, and causes more evaporation. The results of the watermelon experiment showed that soil moisture before seeding would not affect the yield during the years of using gravel mulch. Watermelon yield and WUE were higher for 1-2 and 0.3-1 cm treatments than 2-6 cm treatments in later experiments during 2006 and 2007. In conclusion, 2-6 cm large size particles would not account for much in gravel-sand mulching layer. It would be better if the percentage of 2-6 cm particles was less than 30%.     

Evaluation of the influence of irrigation methods and water quality on sugar beet yield and water use efficiency

Rapid urbanization and industrialization have increased the pressure on limited existing fresh water to meet the growing needs for food production. Two immediate responses to this challenge are the efficient use of irrigation technology and the use of alternative sources of water. Drip irrigation methods may play an important role in efficient use of water but there is still limited information on their use on sugar beet crops in arid countries such as Iran. An experiment was conducted to evaluate the effects of irrigation method and water quality on sugar beet yield, percentage of sugar content and irrigation water use efficiency (IWUE). The irrigation methods investigated were subsurface drip, surface drip and furrow irrigation. The two waters used were treated municipal effluent (EC = 1.52 dS m⁻¹) and fresh water (EC = 0.509 dS m⁻¹). The experiments used a split plot design and were undertaken over two consecutive growing seasons in Southern Iran. Statistical testing indicated that the irrigation method and water quality had a significant effect (at the 1% level) on sugar beet root yield, sugar yield, and IWUE. The highest root yield (79.7 Mg ha⁻¹) was obtained using surface drip irrigation and effluent and the lowest root yield (41.4 Mg ha⁻¹) was obtained using furrow irrigation and fresh water. The highest IWUE in root yield production (9 kg m⁻³) was obtained using surface drip irrigation with effluent and the lowest value (3.8 kg m⁻³) was obtained using furrow irrigation with fresh water. The highest IWUE of 1.26 kg m⁻³ for sugar was obtained using surface drip irrigation. The corresponding efficiency using effluent was 1.14 kg m⁻³. Irrigation with effluent led to an increase in the net sugar yield due to an increase in the sugar beet root yield. However, there was a slight reduction in the percentage sugar content in the plants. This study also showed that soil water and root depth monitoring can be used in irrigation scheduling to avoid water stress. Such monitoring techniques can also save considerable volumes of irrigation water and can increase yield.     

The effect of water stress and rootstock on the development of leaf injuries in grapevines irrigated with saline effluent

Deficit irrigation is increasingly being practiced in water-limited areas to overcome water scarcities. Although, this practice reduces yield losses, there is limited information currently available on how this practice can affect crops when the irrigation water contains elevated levels of salts. An experiment was set up to investigate salt uptake and distribution and salt tolerance of potted Soultanina vines grafted on different rootstocks (41B, 1103P, 110R) and irrigated with effluent containing relatively high concentrations of salts and fresh water at different fractions of evapotranspiration (0.50, 0.75 and 1.00ET). Irrigation with recycled water induced the development of leaf burns, which were more intense in 1998 despite the lower leaf-Na and -Cl content. This may have been due to the more severe water deficit and/or to the more adverse climatic conditions which prevailed during that season. Decreasing the irrigation level induced the development of leaf burns causing only minor changes to leaf-Na or -Cl content. Differences in salt uptake, accumulation and distribution were observed among the rootstocks investigated in this work, suggesting that differences exist in the mechanisms regulating salt uptake and distribution in the shoot. Despite these differences, a distinct superiority in terms of salinity tolerance among rootstocks was only observed at the 0.50ET irrigation level, where vines grafted on 41B developed earlier and more acute leaf burns than the other rootstocks. These findings suggest that leaf salt content alone it is not to classify genotypes according to their tolerance to salinity and that salinity-induced damage is linked with prevailing environmental conditions. Furthermore, it can be inferred that grapevines have additional mechanisms to cope with salt stress which may counteract differences in salt uptake and accumulation in the shoot.     

Effects of gravel-sand mulch, plastic mulch and ridge and furrow rainfall harvesting system combinations on water use efficiency, soil temperature and watermelon yield in a semi-arid Loess Plateau of northwestern China

In the northwestern Loess Plateau of China, low precipitation results in poor crop yields, with a great fluctuation from year to year. The adoption of gravel-sand mulching has shown improvements in the growth of crops such as watermelon. The ridge and furrow rainwater harvest system (RFRHS) has been shown as an easy and efficient way to collect rainwater. A field experiment was conducted from 2007 to 2009 at Gaolan, Lanzhou, Gansu, China, to measure the effects of RFRHS, plastic mulch and gravel-sand mulch combinations on soil temperature, evapotranspiration (ET), water use efficiency (WUE) and watermelon yield. There were eight treatments: (1) flat gravel-sand mulched field, (2) RFRHS with a sand mulched furrow, entire plastic mulch and the ratio 1:1 of ridge and furrow, (3) RFRHS with a sand mulched furrow, entire plastic mulch and the ratio 4:3 of ridge and furrow, (4) RFRHS with a sand mulched furrow, entire plastic mulch and the ratio 5:3 of ridge and furrow, (5) RFRHS with a sand and plastic mulched furrow, bare ridge and the ratio 4:3 of ridge and furrow, (6) RFRHS with an entire plastic mulch and the ratio 4:3 of ridge and furrow, (7) conventional ridge planting with a plastic mulched ridge, and (8) flat gravel-sand mulched field plus 23 mm supplementary irrigation. Soil temperature for RFRHS with a gravel-sand plus plastic mulched furrow was slightly lower than that of flat gravel-sand mulch. The RFRHS caused a significant increase in watermelon yield and WUE. The increase in watermelon yield and WUE was greatly influenced by the ratio of ridge and furrow when RFRHS was combined with gravel-sand mulch. Watermelon yield was highest for the 1:1 ratio, and WUE was highest for the 5:3 and 1:1 ratios of ridge:furrow, and these were significantly greater than that of flat gravel-sand mulch, without or with irrigation. The use of ridge with plastic film mulch increased the beneficial effect of RFRHS on yield. The watermelon yield and WUE for non-plastic-mulched ridge were even lower than that of flat gravel-sand mulch. In summary, the findings suggest that RFRHS with gravel-sand mulched furrow plus plastic film mulch, and 1:1 ratio of ridge:furrow, would facilitate the use of limited rainfall most efficiently in improving watermelon yield, by reducing ET and increasing WUE in this semiarid region.     

Effects of planting density on the productivity and water use of tea (Camellia sinensis L.) clones: I. Measurement of water use in young tea using sap flow meters with a stem heat balance method

Sap flow meters based on the stem heat balance method were used to measure the mass flow rates or water use in young potted tea (Camellia sinensis L.) plants of clones AHP S15/10 and BBK35. The meters were constructed on site and installed onto the stem or branch sections of field growing plants in an experiment originally designed to study the effects of plant population density and drought on the productivity and water use of young tea clones. The objective of the study was to use the SHB method as a first attempt to use sap flow meters for determining the water use of young tea growing in the field under well watered conditions in Tanzania. The results are reported and recommendation made for further work on using the technique.