The potential of intercropping as an alternative land use system in temperate North America

The success of many intercropping systems in North America is attributable to the generation of a short term return from an agricultural crop during the early, unprofitable years of a longer term crop that is fruit, nuts or wood. This highly-efficient use of land and related profitability are important not only in the development of intercropping systems per se, but also in other applications which have tremendous potential independent of profitability. For example, intercropping can be effectively used during the establishment phases of hardwood plantations where it is essential to have a high level of weed control, the costs of which are often recovered with the agricultural production. Intercropping can also be used to grow trees rapidly and with a form that can be easily integrated into recreational or park situations, or urban fringe areas. In an urban context, intercropping can be used to grow trees in agricultural areas that are likely to be developed where traditional forestry options are not appropriate and the value of younger, thrifty trees may enhance property values far in excess of the cash value of the wood.     

A study of the bonding forces between the epithelial cells surrounding the resin canals of slash pine (Pinus elliottii Engelm.) holocellulose

Summary Although the bonds between the cellular components of pine epithelia (isolated from holocellulose) can be strengthened by the addition of multivalent ions such as those of calcium, iron, uranium, etc., it was observed that these bonds are only weakened and not destroyed by the removal of the ions from the tissues. Reagents, such as KOH and K₂SO₄, which do not yield soluble calcium salts, do not cause a discernible weakening of the bonds between the cellulose components of epithelia pretreated with Ca ion. Washing the weakened epithelia with water causes them to swell. The separation of epithelial cells occurs only after the application of mechanical forces to the tissues. Electron microscopic examination of the swollen and unswollen tissues shows that fibrils and lamellae extend between the individual cells which must be destroyed by mechanical action before cell separation can occur. The swelling of the tissues by washing after removal of multivalent ions was attributed to the expansion of electrical double layers and to the increasing osmotic pressure from the increasing Donnan potential, while the difference in swelling as a result of HCl treatment vs. KCl and K₄Fe(CN)₆ was attributed to differences in charge development and to hydrogen bonding between acidic components. The restrengthening of the tissue as a result of the readdition of multivalent ion was attributed to the collapse of the electrical double layers and the reduction of the Donnan potential, with the re-forming of bonds between the components of the epithelia. Evidence suggesting that multivalent ions actually participate in bonding was obtained and although the nature of the bonding cannot be determined, both salt formation and complex formation between the ions and the components of the tissues is suggested.     

The effect of composition on the effectiveness and fixation of copper-chrome-arsenic and copper-chrome preservatives part I: Effectiveness

Summary A preliminary study of a wide range of copper-chrome-arsenic formulations indicates that the most offective are in the region, CuSO₄·5H₂O-35 to 45 per cent; K₂Cr₂O₇-40 per cent and above; As₂O₅·2H₂O-25 to 15 per cent or less. Effectiveness appears to depend more on the copper content than the copper-arsenic. Observations on selective absorption and leaching suggest that the chromium fixes the arsenic preferentially to the copper. Although there appears to be no major amount of fixation of copper by arsenic, at the start of addition of arsenic to copper-chrome formulations there is a small but significant decrease in the leaching of the copper suggesting either a small amount of fixation of copper by arsenic or the formation of an insoluble complex of all three components.Maximum fixation of arsenic was obtained when the Cr/As ratio (as salts) was 1.9 or greater. Maximum fixation of copper is not so simply defined but is round about a Cr/Cu ratio (as salts) of 1.7.The area of maximum effectiveness is not coincident with the area of maximum fixation of both copper and arsenic but slightly displaced towards a region of higher copper where there is still maximum fixation of arsenic but some loss of copper.     

Relationships between preference, rumen degradability, gas production and chemical composition of browses

The aim of this work was to assess whether degradability, gas production or chemical constituents could predict the preference of browses. Forty tropical browse species leaves with a crude protein (CP) content ranging from 79 to 307 g kg^-1 DM were used for this study. The neutral detergent fibre (NDF) ranged from 220 to 694 g kg^-1 DM, while acid detergent fibre (ADF) ranged from 146 to 523 g kg^-1 DM. The NDF-bound nitrogen (NDFN) and ADF-bound nitrogen were particularly high in Calliandra calothyrsus, Acacia polyacantha, Sesbania sesban, Acacia venosa and Acacia hockii. High levels of tannins were observed in Acacia species especially A. dolichocephala, A. hockii, A. microbotrya and A. salicina. High levels were also observed in Flemingia macrophyla and Leucaena pallida. The browse species differed (P < 0.05) in DM in sacco degradability coefficients. High potential degradability (PD) and effective degradability (ED) were observed in Sesbania spp, Moringa stenopetala, Indigofera arrecta, Chamaecytisus palmensis and Atriplex spp. The browses differed (P < 0.05) in asymptotic gas (Ag) production (ml g^-1 OM), but had similar (P > 0.05) times of incubation at which half of the asymptotic gas had been formed. Preference and DM intake were positively correlated (P < 0.01) to NDFN, but negatively correlated (P < 0.05) to NDF and ADF. The PD and Ag were negatively (P < 0.001) related to NDF, ADF and lignin. Total phenols (TP) and condensed tannins (CT) were negatively (P < 0.05) related to PD, ED and Ag. A positive correlation was observed between CT and NDF-bound condensed tannins (r = 0.55, P < 0.001) and, CT and TP (r = 0.40, P < 0.01). Prediction equations were poor for DM intake and preference, moderate for gas production and good for potential and effective degradabilities. The phenolic components were more related to dry matter degradation and gas production than to preference and dry matter intake. NDFN and Ag made a positive contribution to both preference and DM intake. It was concluded that chemical constitutes such as N, NDF, NDFN, ADF and lignin are essential to predict the nutritive value of browses. This revised version was published online in June 2006 with corrections to the Cover Date.     

Microclimate and soil moisture effects of three intercrops on the rows of a newly-planted intercropped plantation

Trees are grown in intercropping systems for a variety of purposes including wood products, fuelwood, fruit, forage or conservation purposes. No matter what end use, different tree/crop combinations interact differently resulting in differential growth rates of the trees during establishment. Preliminary work has shown that seedling growth and survival of trees are related to their intercrop and the results of this study help to explain these findings. Soil water potential, soil and air temperature, relative humidity, windspeed, and light (photosynthetic photon flux density — PPFD) were measured throughout the growing season in the clean-weeded treerows within crops of corn, soybeans and winter wheat. Crop height and biomass were also measured. This study was conducted during the 1992 growing season which was unusually cool and wet from mid June into the winter. The growth of winter wheat, measured by crop height and above-ground biomass, was earlier in the season than that of soybeans and corn, and this pattern affected the environmental conditions in the tree rows. Soil water potential was affected with associated effects on soil temperature (in combination with other factors). Crop height drastically reduced windspeed in the corn treatment from July through winter, also affecting PPFD and soil temperature later in the year. Although many microclimate differences were relatively small, data from subsequent years as well as associated soil moisture studies and additional years will help to further elucidate these relationships.     

The effect of composition on the effectiveness and fixation of copper/chrome/arsenic and copper/chrome preservatives part II: Selective absorption and fixation

Summary Observations on selective absorption and leaching suggest that the chromium fixes the arsenic preferentially to the copper. Although there appears to be no major amount of fixation of copper by arsenic, at the start of addition of arsenic to copper-chrome formulations there is a small but significant decrease in the leaching of the copper suggesting either a small amount of fixation of copper by arsenic or the formation of an insoluble complex of all three components.Maximum fixation of arsenic was obtained when the Cr/As ratio (as salts) was 1.9 or greater. Maximum fixation of copper is not so simply defined but is round about a Cr/Cu ratio (as salts) of 1.7.The area of maximum effectiveness is not coincident with the area of maximum fixation of both copper and arsenic but slightly displaced towards a region higher copper where there is still maximum fixation of arsenic but some loss of copper.     

Landowner perceptions and the adoption of agroforestry practices in southern Ontario,Canada

A mail-out survey questionnaire was developed by the Agroforestry group at the University of Guelph to determine the level of awareness and interest in the adoption of agroforestry systems by landusers from four townships in Wellington County, Ontario. The questionnaire investigated: (1) the current level of knowledge regarding windbreaks, woodlots and plantations, intereropping, riparian plantations and silvipasture, (2) the present level of participation in each of these systems on-farm, (3) the perceived benefits and/or drawbacks of each of these initiatives with respect to total farm income, income diversity, land rehabilitation, land value/equity, soil/water conservation, labour intensity, overhead and return on the term of investment.The majority of respondents were familiar with conventional agroforestry systems such as windbreaks and woodlots/plantations (80%, 62% respectively), therefore the level of interest in the adoption of these practices was significant (74%, 66% respectively). Response rates were lower for silvipasture, riparian plantations and intercropping, most likely as result of the low level of familiarity with these practices (20%, 32%, 4% respectively). Respondents commented that agroforestry systems would have a neutral effect on farm income, and would increase land stewardship. In some cases, interested landusers indicated a willingness to participate in agroforestry systems even though they anticipated increases in overhead and labour intensity; however, this was only true if they held land stewardship as a priority. Landusers were more concerned with the economic aspects of agroforestry, as a determinant to the future adoptability of particular practices. Age, gender, farm operation and farm size were not correlated with the adoption of agroforestry systems.The success of agroforestry programs on farms in the study area is largely dependent on the attitudes and willingness of landusers to participate in non-traditional agricultural systems.     

白马鸡人工驯养初步研究

通过人工饲养的方式探索出白马鸡驯养的经验,即:在野生白马鸡适宜生境下建立饲养场,从育雏阶段开始进行人工投食饲养和本地土鸡带领相结合的驯养方式。目前已经完成从子一代到子二代的完整驯养、饲养流程,取得了云南省林业厅的驯养繁殖许可证。对育雏、亚成体、成体阶段的喂食量、存活情况等作了分析,认为接近原始生境的环境及本地带雏母鸡是成功的重要条件。     

不同土地利用类型氨挥发氮同位素自然丰度特征

为了探讨不同土地利用类型下氨（NH3）挥发氮同位素自然丰度特征,采集3种土地利用类型（果园、菜地和林地）土壤,在可控条件下采用海绵吸收法开展了为期15d的室内培养试验,测定了不同土地利用类型下土壤NH3挥发全过程δ15N值及其变化规律。培养期间,3种土地利用类型下的土壤NH+4-N浓度均呈现先上升后下降的趋势;果园和菜...