常绿和落叶阔叶树叶中N和P的变化及转移

从叶完全展开到生长季结束对常绿阔叶树种铁冬青、红楠和海桐及落叶阔叶树种日本朴、银杏和木叶的N和P浓度进行了定期测定。结果表明,常绿阔叶树种新叶的N和P浓度从5—7月急剧下降,然后小幅波动,而老叶的N和P浓度变化缓慢。落叶阔叶树种的N和P浓度随着季节的推移而明显下降。大多数树种的P转移率大于N转移率。常绿阔叶树种的N和P的转移率大于落叶阔叶树种。     

Modelling agroforestry systems of cacao (Theobroma cacao) with laurel (Cordia alliodora) and poro (Erythrina poeppigiana) in Costa Rica II. Cacao and wood production,litter production and decomposition

During 7 years (1979–1985) cacao harvests (beans and husks) have been recorded for the agroforestry systems ofTheobroma cacao underCordia alliodora andErythrina poeppigiana shade trees. The mean oven dry cacao yields were 626 and 712 kg.ha⁻¹.a⁻¹ cocoa beans underC. alliodora andE. poeppigiana respectively. Harvests have gradually increased over the years and the plantation has now reached maturity. Annual extraction of N, P, K, Ca and Mg in fruits, which is relatively small, was calculated on the basis of chemical analyses. The following average values were found (kg.ha⁻¹.a⁻¹): At the age of 8 years, theC. alliodora trees have reached 26.7 cm diameter (DBH) and 14.0 m in height. Mean annual growth (from age 5 to 7) is 14.6 m³.ha⁻¹.a⁻¹. Natural plant residue production has been measured for 4 years (Nov. 1981–Oct. 1985). UnderE. poeppigiana it has reached a value of 8.91 t.ha⁻¹.a⁻¹ and underC. alliodora 7.07 t.ha⁻¹.a⁻¹. The shade trees have contributed 57 and 47% respectively. Transference and decomposition rates are high and important in the nutrient cycles. The nutrient content of the litter was analysed and corresponding average yearly transfers were (kg.ha⁻¹.a⁻¹): For part I see Vol. 4, No. 3, 1986. Agroforestry Project, CATIE/GTZ (Tropical Agricultural Research and Training Center/Gesselschaft für Technische Zusammenarbeit), Turrialba, Costa Rica     

宁夏引黄灌区灌淤土壤磷累积状况及磷肥肥效研究

宁夏第二次土壤普查结果表明,灌淤耕地速效磷含量明显提高,平均含量由1985年的16.3 mg/kg增加到现在28.04 mg/kg.吴忠市利通区东塔乡国家农业科技示范园区磷肥肥效试验研究表明:土壤速效磷含量在50～60 mg/kg高水平下,小麦套玉米施磷效果较低,小麦玉米总产量肥料函数效应达显著水平.施P2O5最大量1...     

施磷量对旱地小麦氮磷钾和干物质积累及产量的影响

针对目前农业生产中存在的施肥增产效应下降问题,研究了磷肥用量对冬小麦养分、氮磷钾和干物质积累及产量的影响,以期为高产高效施肥提供依据.在黄土高原旱地进行田间试验,设不施磷,施磷P2O5 50kg/hm2(不足)、P2O5 100 kg/hm2(适量)和P2O5 150 kg/hm2(高量)4个水平,在不同生长期采样测定...     

陕北不同土地利用类型下土壤无机磷形态分布及有效性研究

采用蒋柏藩-顾益初无机磷分级方法,对黄土高原两种农田土壤剖面(0～100 cm)中无机磷形态分布特征进行了研究.结果表明:两种农田土壤剖面(0～100 cm)中无机磷形态占全磷的90.95%;无机磷又以Ca-P为主,所占比例在87.86%～92.55%之间;糜子地土壤剖面中无机磷总量、Ca2-P、Ca8-P、Al-P和...     

Scion-rootstock relationships with respect to height growth and foliar concentrations of nitrogen and phosphorus in reciprocal grafts of Pinus caribaea var. hondurensis

Both scion and rootstock clones significantly influenced scion elongation and concentrations of nitrogen and phosphorus in the scion foliage. Scion clone was the more important determinant. Scion clone × rootstock clone interactions were not significant. The ability of a clone to elongate as a scion was not correlated with its capacity to promote or retard scion elongation when used as a rootstock. Genetic differences in foliar nutrient concentrations appeared to reflect levels of nutrient demand, rather than the ability of roots to absorb nutrients. Nutrient demand of the rootstock can also explain negative correlations between nitrogen levels in rootstock clones and levels of both nitrogen and phosphorus in the scions. There was no significant relationship between scion elongation and foliar nitrogen concentrations of either rootstock or scion. The weak relationship between scion elongation and concentration of phosphorus in the rootstock apparently resulted from tissue dilution.     

氮磷钾对绿玉菊生长的影响

采用水培方式,探讨不同浓度水平氮、磷、钾对绿玉菊生长的影响。分析了不同浓度氮、磷、钾处理下绿玉菊的株长、根长、叶绿素含量、丙二醛含量的关系。结果表明绿玉菊的株长和叶绿素含量随氮肥浓度的增加而增长;处理5(含氮7.5mmol.L-1,含磷0.2mmol.L-1,含钾3mmol.L-1)最符合绿玉菊水培生长要求。     

磷肥用量对冬作马铃薯镁素积累与分配特征的影响

以费乌瑞它脱毒种薯为材料,通过大田试验研究4个磷肥水平,即0(P0)、45.0(P1)、90.0(P2)、135.0(P3)kg/hm~2对冬作马铃薯镁积累与分配特征的影响。结果表明:各处理马铃薯整株镁积累量呈先升高后降低变化趋势,齐苗后17~45 d为快速积累期,在齐苗后59 d出现峰值,齐苗后73 d,各处理全株镁积累量表现为:P1P2P3P0;块茎镁积累量呈持续升高趋势,齐苗后73 d,各处理块茎镁积累量表现为:P1P2P3P0,但各处理间并未产生显著差异;各处理镁在叶片中的分配比例均呈逐渐降低趋势;镁在茎中的分配比例整体呈逐渐降低趋势,变幅不大,而在块茎中的分配比例呈持续上升趋势;整个生育期间,镁在各生育阶段各器官的分配比例呈现:叶茎(齐苗后3 d);叶茎块茎(齐苗后17 d);叶块茎茎(齐苗后31~45 d);块茎叶茎(齐苗后59~73 d)的动态变化过程,镁在块茎中的分配率以P1处理最大,为60.38%。供试条件下,磷肥施用量在P1水平下可提高马铃薯镁积累量,P2、P3水平的用量则会降低镁的积累;平均每生产1 000 kg块茎,植株需从土壤中吸收镁0.253 kg.     

Monitoring and modelling total phosphorus contributions to a freshwater lake with cage‐aquaculture

A mass‐balance modelling approach combined with a sensitivity analysis was utilized to gain an improved understanding of the relative contributions of phosphorus (P) loading from various anthropogenic and non‐anthropogenic sources into Lake Wolsey (Manitoulin Island, Ontario, Canada), a Type 2 freshwater lake with a cage‐aquaculture facility. Total P loadings were estimated from eight sources (inlet exchange, non‐point sources, cage‐aquaculture facility, internal loading, groundwater seepage, atmospheric deposition, leaf litter and dwellings) and three sinks (outlet exchange, sedimentation and sportfishing). Results indicated that over the study period (May–November 2007) the non‐point sources were the leading contributor of total P to Lake Wolsey (1120 kg P) followed by the cage‐aquaculture facility loading (915 kg P), inlet exchange (539 kg P), groundwater inputs (305 kg P), dwellings (219 kg P), internal P recycling loads from the hypoxic hypolimnion (186 kg P), atmospheric deposition (79 kg P) and decomposing leaf litter (8.1 kg P). When comparing the loadings in this study, the sensitivity analysis showed that non‐point sources were the only significant input parameter of total P loading to the in‐lake concentrations of P in Lake Wolsey(P = 0.05). Information from this project will provide water quality managers with sound scientific information to make defencible decisions pertaining to policy and regulatory approaches for water quality risk assessment and management of cage‐aquaculture in Type 2 sites.     

Phosphorus utilization in juvenile Clarias gariepinus fed phytase-supplemented diets based on soya bean (oil-extracted) and full-fat (roasted): A comparison

The effect of microbial phytase on phosphorus utilization in juvenile Clarias gariepinus (initial fish body weight 11.55 ± 0.2 g) was tested on two different diets based on oil-extracted soya bean (Experiment 1) and roasted soya bean meal (Experiment 2) using a 5 × 5 experimental design for 84 days. The basal isonitrogenous and isocaloric diets for oil-extracted and roasted soya bean were formulated to replace fish meal at 25% (S1E), 50% (S2E), 75% (S3E), 100% (S4E); and 25% (S1), 50% (S2), 75% (S3), 100% (S4), respectively. Each treatment was replicated four times. Microbial phytase was supplemented in each replicate at 250 FTU/g (P1), 500 FTU/g (P2), 750 FTU/g (P3), and 1,000 FTU/g (P4). Basal controls, which included a fish meal-based diet (S0), were not supplemented with phytase (P0). The result in Experiment 1 showed that there was a significant increase in whole-body protein and reduction in fat with phytase compared to a diet without phytase (P < 0.05). Serum total protein declined significantly with phytase supplementation (P < 0.05). Serum phosphorus and glucose were higher with phytase supplementation compared to control (P < 0.05). Bone minerals declined significantly with increasing level of soya bean compared to fish meal diet (P < 0.05). In Experiment 2, serum phosphorus was improved with phytase compared to control with no phytase (P > 0.05). A significant reduction in whole-body protein and increase in fat was observed for fish fed phytase diets compared to diets with no phytase, regardless of soya bean level (P < 0.05); however, ash content was improved with phytase (250 FTU/g) compared to control (P < 0.05). Phytase supplementation improved bone phosphorus (250 FTU/g), calcium (250 FTU/g), magnesium (250–500 FTU/g), and zinc (250–1,000 FTU/g) compared to control (P < 0.05). In conclusion, the research has demonstrated that improved bone phosphorus (P) and growth could be achieved with the supplementation of dietary phytase.