土壤水分特征曲线在作物非充分灌溉适宜水分下限确定中的应用

SPAC系统中水总是从水势高处流向水势低处,土壤水势的高低是影响植物根系吸水速率的主要因素。相对于土壤含水量来说,用土壤水势作作物非充分灌溉的下限指标更具科学性,更利于水分下限指标的推广应用。试验结果表明,对于整个生育期来说,-200 kPa是比较适宜的大棚番茄土壤水势下限。在这一指标的推广过程中,须先测定当地土壤水分特征曲线,并从曲线上找出该适宜水势对应的土壤含水量,通过控制土壤含水量达到控制土壤水势的目的,从而实现精量灌溉。

不同水肥条件对马铃薯肥料N利用率的影响

在旱棚控制条件下 ,用五因素五水平二次回归正交旋转组合设计 ,研究了水肥施用分配 ,补水量 ,施N量 ,施K量 ,有机肥施用量的综合作用效应 .结果表明 ,五因素对肥料N利用率的作用顺序为施N量 >补水量>水肥施用分配 >有机肥施用量 >施K量 .水肥施用分配相对于不同水、化肥 (N、K )、有机肥量的选择 ,可以大大地提高肥料N利用率 ;量少应重前施用 ,量多重后施或均施为好 .补水量与施N量的耦合规律为 :高水高肥效果最佳 ,肥料N利用率可达 5 7 83 % ,中水中N及低水低N次之 ,为 2 9 17%～ 40 99% ;高水低N或低水高N导致最低的利用率 ,为 2 2 87%或 2 2 5 1%

延安日光温室蔬菜生产现状与发展对策

延安日光温室蔬菜生产从初步发展走向稳定健康发展 ,基础设施建设、栽培技术等取得了一定成绩 ,但技术力量仍感不足 ,农药、化肥污染愈加严重。提出今后进一步发展的对策

连作对设施黄瓜产量和品质及土壤酶活性的影响

揭示黄瓜产生连作障碍的机理,为设施蔬菜的可持续发展和减轻连作障碍提供参考依据。【方法】在日光温室内进行田间试验,以露地玉米地土壤为对照,研究不同连作年限(4,5,8和12年)下黄瓜产量和品质及土壤酶活性的变化。【结果】随着黄瓜连作年限的增加,黄瓜产量、可溶性固形物和维生素C含量均下降,硝酸盐含量上升,土壤呼吸强度降低,土壤脲酶活性、蔗糖酶活性、碱性磷酸酶活性均呈先上升后降低的趋势;随着黄瓜生长季节的变化,土壤脲酶活性呈先上升后降低再升高的趋势,土壤蔗糖酶活性、碱性磷酸酶活性和土壤呼吸强度均呈先上升后降低的趋势。【结论】随着连作年限的延长,设施黄瓜的产量和品质均下降,土壤脲酶、蔗糖酶和碱性磷酸酶活性均呈先升高后降低的趋势。

农田土壤有机碳的影响因素及其研究

大气温室效应气体N2O、CO2增多与全球气温变暖有着密切的关系,由于农业活动导致的碳排放量占碳总排放量的25%,因此研究农田土壤有机碳的影响因素,对增加农田碳素固定和保持,减少由于不合理的土地使用而导致大量CO2的排放,维持农业和生物圈生态系统的可持续发展有着重要意义。本文分析了温度、水分、土地开垦、休闲和撩荒、耕翻、轮作、秸秆还田、肥料管理等对土壤有机碳的影响。减少翻耕次数,增加秸秆还田,优化氮、磷、钾等养分用量及配比,是提高农田,尤其是旱地农田土壤有机碳含量,培肥、改良土壤的重要途径。

有机钾肥在日光温室蔬菜上的应用效果研究

对陕北黄土高原日光温室大棚蔬菜黄瓜、大青菜、油麦菜和西芹进行了叶面喷施富万钾有机钾肥的田间试验研究。结果表明,在日光温室大棚蔬菜上施用有机钾肥,黄瓜植株高度、叶片数、茎粗、叶面积、瓜长均增加。大青菜的茎粗增长44%。油麦菜的株高、茎粗、地上植株、地下根重、总生物量均明显增加。西芹的株高、茎粗、地上植株、地下根重以及总生物量增加。富万钾有机钾肥能明显促进蔬菜生长,提高产量。

设施条件下氮肥对大青菜硝酸盐及土壤矿质氮累积的影响

采用田间实验研究了施用氮肥对设施条件下大青菜生长发育和产量,以及对土壤硝酸盐含量累积分布的影响。结果表明,在施氮肥0~500 kg hm-2范围内,氮肥施用量越大,产量越高,但到达一定量时,便不能再促进产量的提高,反而会引起减产。土壤铵态氮含量随着土壤剖面向下不断下降,表层的铵态氮含量较高,土壤硝态氮含量在整个土壤剖面的分布变化较小,但也是从表层向下处于一种缓慢减少的趋势,铵态氮的累积主要集中在上部土壤剖面,硝态氮的累积分布在整个土壤剖面,土壤硝态氮含量随施肥量增加而增加;氮肥施用量对硝酸盐含量有很大影响。在施氮肥0~700kg hm-2范围内,氮肥施用量越多,大青菜硝酸盐含量越高。

蔬菜温室土壤某些化学性质的演变特征

To explore the changes of soil chemical properties in vegetable greenhouse,a comparative study was carried out with the samples gathered from vegetable greenhouse fields and their adjacent upland fields in Damintun Town,Xinming County,Liaoning Province.The results showed that compared with upland fields,the contents of soil organic carbon and total nitrogen in greenhouse fields increased significantly.At the depth of 0～30 cm,soil organic carbon in greenhouses of 1-,4-and 10-year increased by 31.09%,35.44%,and 66.80%,respectively,compared with the upland soil.Soil nitrate content at the depth of 0～30 cm in greenhouse fields was 5.05～12.49 times as much as that in upland fields.The nitrate content in different soil layers increased with the increasing age of greenhouse field.,e.g.,at the depth of 20～30 cm,soil nitrate content was significantly higher in 10-year than in 1-and 4-year greenhouse field,with an increase of 65.73% and 50.89%,respectively,and 6.55 times as much as that in upland field,which indicated that soil nitrate transported downwards,and obviously enriched in deeper soil layers under heavy application of fertilizer.Also with the increasing age of greenhouse field,soil pH decreased,while soil soluble salts accumulated.

Simulation study of China's net primary production

Spatial and temporal distribution of vegetation net primary production (NPP) in China was studied using three light-use efficiency models (CASA, GLOPEM and GEOLUE) and two mechanistic ecological process models (CEVSA, GEOPRO). Based on spatial and temporal analysis (e.g. monthly, seasonally and annually) of simulated results from ecological process mechanism models of CASA, GLOPEM and CEVSA, the following conclusions could be made: (1) during the last 20 years, NPP change in China followed closely the seasonal change of climate affected by monsoon with an overall trend of increasing; (2) simulated average seasonal NPP was: 0.571 +/- 0.2 GtC in spring, 1.573 +/- 0.4 GtC in summer, 0.6 +/- 0.2 GtC in autumn, and 0.12 +/- 0.1 GtC in winter. Average annual NPP in China was 2.864 +/- 1 GtC. All the five models were able to simulate seasonal and spatial features of biomass for different ecological types in China. This paper provides a baseline for China's total biomass production. It also offers a means of estimating the NPP change due to afforestation, reforestation, conservation and other human activities and could aid people in using for-mentioned carbon sinks to fulfill China's commitment of reducing greenhouse gases.

Potential CO2 Emission Reduction by Development of Non-Grain-Based Bioethanol in China

Assessment of the potential CO2 emission reduction by development of non-grain-based ethanol in China is valuable for both setting up countermeasures against climate change and formulating bioethanol policies. Based on the land occupation property, feedstock classification and selection are conducted, identifying sweet sorghum, cassava, and sweet potato as plantation feedstocks cultivated from low-quality arable marginal land resources and molasses and agricultural straws as nonplantation feedstocks derived from agricultural by-products. The feedstock utilization degree, CO2 reduction coefficient of bioethanol, and assessment model of CO2 emission reduction potential of bioethanol are proposed and established to assess the potential CO2 emission reduction by development of non-grain-based bioethanol. The results show that China can obtain emission reduction potentials of 10.947 and 49.027 Mt CO2 with non-grain-based bioethanol in 2015 and 2030, which are much higher than the present capacity, calculated as 1.95 Mt. It is found that nonplantation feedstock can produce more bioethanol so as to obtain a higher potential than plantation feedstock in both 2015 and 2030. Another finding is that developing non-grain-based bioethanol can make only a limited contribution to China's greenhouse gas emission reduction. Moreover, this study reveals that the regions with low and very low potentials for emission reduction will dominate the spatial distribution in 2015, and regions with high and very high potentials will be the majority in 2030.

Cultivation of the intertidal brown alga Hizikia fusiformis (Harvey) Okamura: mass production of zygote-derived seedlings under commercial cultivation conditions, a case study experience

Mariculture of the brown alga Hizikia fusiformis (Harvey) Okamura as an export-oriented human food has been there more for than 20 years in China. It is now one of the five major farmed algal species along the Chinese coast. Stable and sufficient supply of young seedlings for scaling up the cultivation has been a problem throughout the farming history of this species due to the unique dioecious life cycle and relatively short time window of sexual reproduction in nature. These two factors led to a practical difficulty in obtaining zygotes at identical developmental stage in viable amounts for seedling production. A key solution to this problem is to control the synchronization of the receptacle development and to realize the simultaneous discharge of male and female gametes, such that the fertilization rate could be greatly enhanced. Focusing on one of the farmed populations in this report, we present our results on mass production of seedlings using the synchronization technique on a large scale performed in 2007. Totally 5.5 hundred million embryos were obtained from 100 kg female sporophytes. The seedlings were raised up to 3.5 mm in length in greenhouse tanks over a month and were further grown in open sea for over 3 months at two experimental sites. The success of mass production of seedlings in this alga helped to lay the basis for future trials in other species in the genus of Sargassum that have identical life cycle.

Photoperiodic long-day control of sporophyll and hair formation in the brown alga Undaria pinnatifida

Two photoperiodic responses, the development of sporophylls and hairs, have been quantified in sporophytes of the brown alga Undaria pinnatifida. In a final experiment, the algae were cultivated in outdoor, 2000-L seawater tanks in a greenhouse for up to 12 weeks, and daylength was regulated by automatic blinds mounted on top of the tanks. Vegetative young sporophytes were treated under short-day (SD; 8 h light per day) or long-day conditions (LD; 16 h light per day), at 12 h light per day or in a night-break regime (NB; 8 h light per day, 7.5 h dark, 1 h light, 7.5 h dark). The earliest sporophyll development was observed 6, 7 or 9 weeks under LD, NB or SD conditions, respectively. After 12 weeks the sporophylls were significantly longer and wider under LD or NB conditions than in the SD regime, and only half of the experimental algae had formed sporophylls under SD conditions, but all algae under LD or NB conditions. In a foregoing 7-week culture experiment performed in 300-L indoor tanks, enhanced sporophyll formation had also been observed under LD and not under SD conditions (NB omitted). In both experiments, blade elongation rates remained high until the end of the experiments in SD, but declined during sporophyll initiation in LD, NB or at 12 h light per day. Another difference caused by photoperiod was observed in regard to the development of surface hair spots which occurred in both experiments on the blades in LD, NB or at 12 h light per day with identical densities, but were completely lacking under SD conditions. It is concluded that U. pinnatifida is a facultatative long-day plant in regard to reproduction forming vigorously sporophylls in long days, and an obligate long-day plant in regard to hair formation.

Assessment of calcareous alga Corallina pilulifera as elemental provider

Calcareous algae such as Corallina pilulifera a Postels et Ruprecht can be one of the most potential candidates to be used in biological carbon dioxide assimilation to reduce greenhouse effect because of its calcification capacity as well as photosynthesis if utilized extensively and properly. The major elemental composition in C. pilulifera is as follows: sodium 0.13%, chloride 1.75%, magnesium 4.37%, calcium 18.4%, iron 0.31%, and carbonate 28.5%. Calcareous algae can be used as elemental provider for livestock or agriculture. (C) 1999 Elsevier Science Ltd. All rights reserved.

Cultivation of the brown alga Hizikia fusiformis (Harvey) Okamura: stress resistance of artificially raised young seedlings revealed by chlorophyll fluorescence measurement

Commercial farming of the intertidal brown alga Hizikia fusiformis (Harvey) Okamura in China and South Korea in the sea depends on three sources of seedlings: holdfast-derived regenerated seedlings, young plants from wild population and zygote-derived seedlings. Like many successfully farmed seaweed species, the sustainable development of Hizikia farming will rely on a stable supply of artificial seedlings via sexual reproduction under controlled conditions. However, the high rate of detachment of seedlings after transfer to open sea is one of the main obstacles, and has limited large-scale application of zygote-derived seedlings. To seek the optimal condition for growing seedlings on substratum in land-based tanks for avoidance of detachment in this investigation, young seedlings were grown in both outdoor tanks exposed directly to sunlight and in indoor raceway tanks in reduced, filtered sunlight. Results showed that young seedlings, immediately after fertilization, could withstand a daily fluctuation of direct solar irradiance up to a level of 1800 mu mol photons m(-1)s(-1), and maintained a faster growth rate than seedlings grown in indoor tanks. Detailed experiments by use of chlorophyll fluorescence measurements further demonstrated that the overnight (12 h) recovery of optimal fluorescence quantum yield (F-v/F-m) of seedlings after 1 h treatment at 40 degrees C was 98%, and the 48 h recovery of F-v/F-m of seedlings after 1 h exposure to 1800 mu mol m(-2)s(-1) was 92%. Forty-one-day-old seedlings showed no significant decrease of optimal fluorescence quantum yield at salinity ranging from 30 to 5 ppt for a treatment up to 17 h. Six-hour desiccation treatment did not have any influence on the optimal fluorescence quantum yield. Exposure to 18 mmol L-1 sodium hypochlorite for 10 min did not damage the PSII efficiency, and thus could be used to remove epiphytic algae. The strong tolerance of young seedlings to high temperature, high irradiance, low salinity and desiccation found in this investigation supports the view that mass production of Hizikia seedlings should be performed in ambient light and temperature instead of in shaded greenhouse tanks.

Tank cultivation of the red alga Palmaria palmata: Year-round induction of tetrasporangia, tetraspore release in darkness and mass cultivation of vegetative thalli

Field-collected tetrasporophytes of Palmaria palmata were tumbled in 300-L outdoor tanks from January to August at ambient daylength or in a constant short-day (SD) regime (8 h light per day), both at 10 or 15 degrees C. Tetrasporangia were massively induced after 2.5 months under SD conditions at 10 degrees C and completely lacking at 15 degrees C, both under SD or ambient daylength conditions, with a few tetrasporangia present at 10 degrees C and ambient daylength. Elongation rates of tagged tetrasporophytic thalli peaked from March to April in all four conditions, when the biomass densities in the outdoor tanks were close to 2.5 kg fresh weight m(-2). Under all four conditions, juvenile proliferations started to appear in June from the margins of the old fronds, and attained approximately 1 cm in length by the end of July. Approximately 80% of the tetraspores were released during the first three dark phases in a light/dark regime, and the remaining 20% during the light phases. A minimum of 10 min darkness was observed to trigger spore release. White light inhibited tetraspore release, while a similar number of spores were released in continuous red light or in the light/dark regime, although with no significant differences of spore release during subjective days and nights. Sporelings were successfully derived from the released tetraspores for mass propagation of the male gametophyte in 2000-L outdoor tanks in a greenhouse. Mass production of male gametophytic sporelings of P. palmata was completed two times by SD induction of tetrasporangia at 10 degrees C, release of spores in darkness and culturing the sporelings until they were ready to be propagated vegetatively in greenhouse tanks. One experiment lasted from January to October 2001, with spore release in June, and the second from September to April 2003, with spore release in January. These results may support the development of sustainable, year-round Palmaria farming. (c) 2005 Elsevier B.V. All rights reserved.