Maize Land Research Articles

Response of different maize accessions to pink stem borer Sesamia inferens Walker (Lepidoptera: Noctuidae)

Sesamia inferens (Walker) is the most important Rabi pest of maize causing serious losses in India. The objective of the study was to identify maize landraces with high levels of resistance to S. inferens by screening 427 maize land races sourced from different agro-ecological regions, along with CM 500 and CML 451 as resistant and susceptible checks, respectively under natural conditions during Rabi, 2012-13. The range of average per cent dead hearts observed in land races was 0.0 to 57.14%. The most resistant land races were IC258225, IC319533, IC321053, IC321110, IC321111, IC321119, IC326886, IC331795, IC 338827 and IC 350198 which showed no dead hearts infestation while the susceptible were IC331939, IC340368, IC369174, IC369184, IC406420, IC549985, IC549989, IC549990, IC569669 and IC547811 suffered to the extent of 46.15 to 57.14 % dead hearts. There was no dead hearts infestation on resistant check CM 500 while susceptible check CML 451 showed 50 - 100 % dead hearts. These resistant land races identified are recommended for use in the development of S. inferens resistant maize.

Correlates of Maize Land and Livelihood Change Among Maize Farming Households in Mexico

Summary We use classification tree analysis to identify the primary predictors of a suite of maize land use and livelihood outcomes for smallholder farmers in three regions of Mexico (Sinaloa, Mexico state, and Chiapas). Our analysis identifies regionally specific correlates with change in maize area, yield, and income, spanning demographic, environmental, and social development factors. Our results indicate that there may be opportunities for surplus production and market participation in some rain fed areas. We confirm the significance of regional and inter-regional heterogeneity in farmers’ responses and strategies, underscoring the value of regionally specific policy interventions.

Harmful effects and chemical control study of Mikania micrantha H.B.K in Yunnan, Southwest China

Invasive alien species Mikania micrantha, which originated from Central and South America, has spread quickly and become one of the most seriously invasive weedy species in Yunnan Province, Southwest of China. The harmful effects of this plant on major cash crops and local plant communities have been surveyed in 50 townships of 6 counties of Yunnan Province since 2006. Moreover, bioactivity and selectivity of 20 types of herbicides on M. micrantha and farming crops have been tested and analyzed since 2007. The results showed that M. micrantha is mostly distributed in subtropical and tropical areas of Yunnan, such as Lincang District, Baoshan District and Dehong Prefecture. The species has resulted in a series of negative impacts on farming cash crops and local plant communities. Compared with the control effects of 20 soil and foliar-applied herbicides, soil-applied herbicides Atrazine, Bensulfuron methyl and Prometryne have higher bioactivity and selectivity to M. micrantha germination and seedling. Foliar-applied herbicides Sulfometuron methyl, Starane and Glyphosate have better control efficiency on M. micrantha growth, but the security is low. As a result, it recommends that Atrazine should be used for sugarcane, orchard and rubber land, Glyphosate for non farming land and rubber land, Sulfometuron methyl for forest land, and 2, 4-D for maize land, respectively. Key words: Mikania micrantha, crop yield loss, plant community, chemical control, Yunnan Province.

Temporal Variations in Soil CO2 Efflux Under Different Land Use Types in the Black Soil Zone of Northeast China

The quantification of soil CO2 efflux is crucial for better understanding the interactions between driving variables and C losses from black soils in Northeast China and for assessing the function of black soil as a net source or sink of atmospheric CO2 depending upon land use. This study investigated responses of soil CO2 efflux variability to soil temperature interactions with different soil moisture levels under various land use types including grassland, bare land, and arable (maize, soybean, and wheat) land in the black soil zone of Northeast China. The soil CO2 effluxes with and without live roots, defined as the total CO2 efflux (FtS) and the root-free CO2 efflux (FrfS), respectively, were measured from April 2009 to May 2010 using a static closed chamber technique with gas chromatography. The seasonal soil CO2 fluxes tended to increase from the beginning of the measurements until they peaked in summer and then declined afterwards. The mean seasonal FtS ranged from 20.3±7.8 to 58.1±21.3 mg CO2-C m−2 h−1 for all land use types and decreased in the order of soybean land > grassland > maize land > wheat land > bare land, while the corresponding values of FrfS were relatively lower, ranging from 20.3±7.8 to 42.3±21.3 mg CO2-C m−2 h−1. The annual cumulative FtS was in the range of 107–315 g CO2-C m−2 across all land uses types. The seasonal CO2 effluxes were significantly (P < 0.001) sensitive to soil temperature at 10 cm depth and were responsible for up to 62% of the CO2 efflux variability. Correspondingly, the temperature coefficient Q10 values varied from 2.1 to 4.5 for the seasonal FtS and 2.2 to 3.9 for the FrfS during the growing season. Soil temperature interacting with soil moisture accounted for a significant fraction of the CO2 flux variability for FtS (up to 61%) and FrfS (up to 67%) via a well-defined multiple regression model, indicating that temperature sensitivity of CO2 flux can be mediated by water availability, especially under water stress.

Land Suitability Evaluation for Sustainable Food Security in Kiryandongo Refugee Settlement, Uganda

Realizing sustainable livelihood and food security in refugee situations is often an overwhelming challenge. The focus of this study was on ensuring food self-reliance in Kiryandongo refugee settlement in Uganda. The study employed a multimethod approach, that is both qualitative and quantitative methods were used. A cross sectional survey design was used and primary data was collected using questionnaires and in-depth interview. Experimental method was used in analyzing soil samples for soil organic matter content, soil moisture and soil depth. Suitability classes were derived for each of the assessed variables separately and a generalized suitability was later obtained. Suitability classes were ranked as S 1 (highly suitable), S 2 (moderately suitable) and S 3 (marginally suitable). Each sampling unit was chosen on the basis of soil colour, slope and soil type and crop history. Each sampling unit was captured by the use of GPS and results interpolated to depict the situation and mapping of the entire refugee settlement. The results indicate that areas of high suitability S 1 devoted for maize yielded a production level and would ensure food security. Using mean comparative test for average yields, the study established that there was a strong relationship between maize production and land suitability. Areas of marginal suitability experienced the threat of food insecurity. The study recognized the relevance of land suitability evaluation for planning purposes and in ensuring that land resources are put to maximum use. The study recommended site selection for refugee settlements to undertake land suitability evaluation prior to any allocation for settlement.

Evaluation of a feeding strategy to reduce greenhouse gas emissions from dairy farming: The level of analysis matters

The dairy sector contributes to climate change through emission of greenhouse gases (GHGs), via mainly carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O). Replacing grass silage with maize silage is a feeding strategy to reduce enteric CH4 emission. The effect of this strategy on GHG emissions can be analyzed at three different levels: animal, farm, and chain level. The level of analysis might affect results and conclusions, because the strategy affects not only enteric CH4 emissions at animal level, but also other GHG emissions at farm and chain levels. The objective of this study was to determine if the level of analysis influences conclusions about the GHG reduction potential of increasing maize silage at the expense of grass and grass silage in a dairy cow’s diet. First, we used a linear programming (LP, maximizing labor income) dairy farm model to define a typical Dutch dairy farm on sandy soils without a predefined feeding strategy (i.e. reference situation). Second, we combined mechanistic modeling of enteric fermentation and life cycle assessment to quantify GHG emissions at all three levels. Third, continuing from the diet derived in the reference situation, maize silage was increased by 1 kg DM per cow per day at the expense of grass (summer), or grass silage (winter). Next, the dairy farm model was used again to determine a new optimal farm plan including the feeding strategy, and GHGs were quantified again at the three levels. Finally, we compared GHG emissions at the different levels between the reference situation and the situation including the feeding strategy. We performed this analysis for a farm with an average intensity (13,430 kg milk/ha) and for a more intensive farm (14,788 kg milk/ha). Results show that the level of analysis strongly influences results and conclusions. At animal level, the strategy reduced annual emissions by 12.8 kg CO2e per ton of fat-and-protein-corrected-milk (FPCM). Analysis at farm and chain level revealed first of all that the strategy is not feasible on the farm with an average intensity because this farm cannot reduce its grassland area because of compliance with the EU derogation regulation (a minimum of 70% grassland). This is reality for many Dutch dairy farms with an intensity up to the average. For the more intensive farm, that can reduce its area of grassland, annual emissions reduced by 17.8 kg CO2e per ton FPCM at farm level, and 20.9 kg CO2e per ton FPCM at chain level. Ploughing grassland into maize land, however, resulted in non-recurrent emissions of 913 kg CO2e per ton FPCM. At farm and chain levels, therefore, the strategy does not immediately reduce GHG emissions as opposed to what results at animal level may suggest; at chain level it takes 44 years before annual emission reduction has paid off emissions from land use change.

Evaluation of the effects of intra-row spacing on the growth and yield of maize (zea mays l.) in maize-ginger intercrop in Samara, Northern Guinea Savanna of Nigeria

The field experiment was conducted during the cropping seasons of 2009 and 2010 in Samaru, Zaria, Nigeria to evaluate the effects of various intra-row spaces on the growth and yield of maize intercropped into ginger. The experiment consisted of six treatments laid out in a Randomized Complete Block Design and replicated three times. The data collected were subjected to statistical Analysis of Variance and the treatment means were separated using the New Duncan Multiple Range Test at P< 0.05 level of significance. The results showed that the intercropped maize irrespective of spacing adopted, were consistently superior to the sole maize crop in dry matter production per plant, height per plant, number of leaves per plant and leave area per plant. The best grain yield of 3.78 tonnes/ha was obtained in maize spaced at 75 x 75 cm. The sole ginger crop gave rhizome yield (14.08 tonnes per hectare) was statistically higher than yields obtained in intercropped treatments. The intercropped treatments had yield advantages over the sole crop with maize Land Equivalent Ratio of 23-79%. Therefore, maize at 75 x 75cm in ginger at 20 x 20cm was recommended as the best intercrop.

The impact of slurry application technique on nitrous oxide emission from agricultural soils

Direct nitrous oxide (N2O) emissions from fertilized soils are generally estimated using emission factors. However, the emission factors for N2O emission of applied slurry are not well quantified. The effect of slurry application technique on N2O emission was quantified in field experiments in the Netherlands in order to derive N2O emission factors for (shallow) injected and surface-applied cattle and pig slurries. Fluxes of N2O were measured using a closed flux chamber technique and a photo-acoustic infra-red gasmonitor. Fluxes of N2O were measured 64–83 times on grassland on sandy and clay soils and maize land on sandy soil, in the period 2007–2009. There were large differences in total N2O emission between the years, and differences between treatments were not consistent over the years and sites. The average emission factor of all treatments and years (n=35) was 0.9% of the N applied, which is close to the default IPCC emission factor of 1%. However, the range in emission was large, i.e. from −0.2% to 7.0%. The average emission factor for grassland was 1.7% of the N applied for calcium ammonium nitrate (CAN), 0.4% for shallow injected cattle slurry, and 0.1% for surface-applied cattle slurry. For maize land, the average emission factor for CAN was 0.1% of the N applied, for injected cattle slurry 0.9% and for surface-applied cattle slurry 0.4%. The emission factors for pig slurry applied to maize land were higher than for cattle slurry; 3.6% for injected pig slurry and 0.9% for surface-applied pig slurry. Increasing the N application rate on maize land resulted in higher emission factors for CAN, injected cattle slurry, and injected pig slurry. Concluding, on both grassland and maize land (shallow) injection of slurry increased the average emission factor of N2O in comparison to surface application. Differentiation of N2O emission factors which takes specific factors into account, such as N type and rate and application technique, can improve the quantification of N2O emission from agricultural soils and is needed to derive most efficient options for mitigation.

Multiscale Effects of Management, Environmental Conditions, and Land Use on Nitrate Leaching in Dairy Farms

Nitrate leaching in intensive grassland- and silage maize-based dairy farming systems on sandy soil is a main environmental concern. Here, statistical relationships are presented between management practices and environmental conditions and nitrate concentration in shallow groundwater (0.8 m depth) at farm, field, and point scales in The Netherlands, based on data collected in a participatory approach over a 7-yr period at one experimental and eight pilot commercial dairy farms on sandy soil. Farm milk production ranged from 10 to 24 Mg ha(-1). Soil and hydrological characteristics were derived from surveys and weather conditions from meteorological stations. Statistical analyses were performed with multiple regression models. Mean nitrate concentration at farm scale decreased from 79 mg L(-1) in 1999 to 63 in 2006, with average nitrate concentration in groundwater decreasing under grassland but increasing under maize land over the monitoring period. The effects of management practices on nitrate concentration varied with spatial scale. At farm scale, nitrogen surplus, grazing intensity, and the relative areas of grassland and maize land significantly contributed to explaining the variance in nitrate concentration in groundwater. Mean nitrate concentration was negatively correlated to the concentration of dissolved organic carbon in the shallow groundwater. At field scale, management practices and soil, hydrological, and climatic conditions significantly contributed to explaining the variance in nitrate concentration in groundwater under grassland and maize land. We conclude that, on these intensive dairy farms, additional measures are needed to comply with the European Union water quality standard in groundwater of 50 mg nitrate L(-1). The most promising measures are omitting fertilization of catch crops and reducing fertilization levels of first-year maize in the rotation.

Changes in the soil phosphorus status of agricultural land in the Netherlands during the 20th century

The Netherlands has a high cumulative mean phosphorus (P) balance. In the 20th century, cumulative mean P surpluses were ca. 4500 kg P2O5/ha. The annual surpluses have levelled off because of manure application limits from 1984 onwards. We report the effect of soil type, land use, and manure policy on changes in soil P of fields in the Netherlands during the 20th century. We used data (>5 million soil P tests) from the soil analysis laboratory BLGG AgroXpertus. Our results show that soil P has increased on average to fairly high and high ratings. Differences between regions and between land use have remained high from the first records in the 1930s; on arable land the increase continued until the end of our study period while on grassland no changes are evident in the last decades. In general regions with high livestock density have high soil P status. Soil P increased in the order bulbfields < grassland < arable land < maize land < horticulture, and in the order loess < clay < peat < sand soils. Spatial variations in P values reflect more the market value of the crops and regional availability of animal manure than (fertilizer) recommendations. Manure policy since 1984 has resulted in increasingly tight restrictions on P application from manure and fertilizers, but the effects are not yet clearly reflected in changed trends in soil P.

Nitric oxide emissions from black soil, northeastern China: A laboratory study revealing significantly lower rates than hitherto reported

Nitric oxide (NO) is an important component of biogeochemical cycling of nitrogen, produced via biologically mediated processes of nitrification and denitrification in soils. The production and consumption processes of NO in black soils are not fully understood. We established how moisture and temperature affect NO dynamics for black soil samples of maize land in the temperate zone of northeastern China. The optimum soil moisture for the maximum NO production and emission was determined to be 41% water-filled pore space (WFPS), based on laboratory experiments and modeling. For a given moisture, NO fluxes increased exponentially with soil temperature at any given soil moisture. The optimum soil moisture for the maximum NO emission was constant and independent of soil temperature. The NO consumption rate constant (k) in the studied soil (range 9.31 × 10−6–15.1 × 10−6 m3 kg−1 s−1) was in the middle of the range of similar k values published to date. The maximum NO emission potential for black soils at 25 °C and 15 °C were about 18.6 and 9.0 ng N m−2 s−1, respectively. Based on laboratory results and field monitoring data of soil water content and soil temperature, the average NO fluxes from black soils in the region were estimated to be 10.7 ng N m−2 s−1 for an entire plant growth period. NO emissions likely occur principally in July, associated with optimum soil moisture. The present study suggests that NO fluxes from black soil are much lower than the previous reports from cropland in southern parts of China.

Comparative Land Evaluation approaches: An itinerary from FAO framework to simulation modelling

The FAO framework for Land Evaluation (LE) has been the primary procedure used worldwide to address local, regional, and national land use planning. Despite its widespread and long-term application, the process has been criticised by the scientific community for its qualitative and empirical base, which is not effective to address many new agro-environmental challenges where the dynamic characterisation of the interrelated physical and chemical processes taking place in the soil landscape is a must. In today's environment, the LE expert is asked to choose the best LE methodology considering costs, complexity of the procedure and benefits in handling a specific land evaluation. Unfortunately very little scientific literature supports this choice especially in terms of the comparison of different LE approaches. In this scenario, we performed a forage maize land suitability study by comparing different methods having increasing complexity and costs. The study area was comprised of approximately 2000 ha and was located on the Lodi Plain (Po Valley) of North Italy. The primary land use in the region is forage maize and this study was designed to assess forage maize biomass. Methods were developed and applied to compare the efficacy of procedures of increasing complexity. The range of the 9 employed methods ranged from standard LE approaches to the extensive use of simulation modelling (SWAP and CropSyst), using as data input pre-existing soil information (soil map 1:50,000) and also hydraulic properties measured as well estimated by PTF(pedotransfer functions). The different methods were compared based on both predictive ability and cost. Independent estimates of forage maize biomass were obtained by locally tested remote sensing measurements, and predictive ability was estimated using statistical indexes including correlation, relative variance, and ANOVA to evaluate the mean differences in maize biomass. The level of expertise required to apply a specific methodology was a factor in the cost of the LE. In addition, an increase in method complexity corresponded to a higher quality/quantity of input parameters and as a consequence higher costs. Generally, more complex methods gave better results in terms of their predictive ability but this occurred in much discontinuous steps; this finding contradicts a simplified view on the better performance of more complex and mechanicistic methods. Methods operating on measurements resulted in increased performance relative to those operating on PTF. Furthermore, methods operating on “true” soils without aggregations (i.e. soil-mapping units) exhibited higher performance.

Determination of fermentation rates in maize land races used as forage in central Mexico

Determination of fermentation rates in maize land races used as forage in central Mexico

Permissible manure and fertilizer use in dairy farming systems on sandy soils in The Netherlands to comply with the Nitrates Directive target

Properly managed manures have a high fertilizer equivalency and are thus a valuable source of nutrients in forage production systems. An efficient utilization of these nutrients, however, is limited by the crop's demand for nitrogen (N) and phosphorus (P). Moreover, environmental goals implied by the EU Nitrates Directive impose constraints on the use of manure and mineral fertilizer. Through calculations based on experimental data from various sources, the present study explores the limits on the use of cattle slurry and mineral fertilizer in grass and silage maize production on sandy soils in the Netherlands. The study concludes that cut grasslands can utilize cattle slurry up to average rates of 330–340 kg N/ha (120 kg P 2O 5) per year without exceeding a target value of 11.3 mg nitrate-N/l in the upper groundwater or accumulating P in the soil, provided that (i) appropriate amounts of mineral fertilizer N are supplemented, and (ii) growing conditions are good and the grassland is well-managed. When grassland is commonly used for both cutting and grazing, slurry rates have to be reduced by 60 kg N/ha per year (20 kg P 2O 5) to achieve these targets. Similarly, not more than 170 kg slurry-N/ha (60 kg P 2O 5) per year should be applied to silage maize. When grown on dry soils susceptible to leaching, slurry rates on maize land need a further reduction to 155 kg N/ha per year (=55 kg P 2O 5). When grass and maize are grown in rotation, cattle slurry and fertilizer applications to maize should be reduced even more drastically, whereas application rates to grassland can be extended to compensate for the temporal investment in the new sod. Consequently, from the point of view of N leaching and P accumulation, manure rates should be determined by (i) the harvest regime of the grass, (ii) the proportions of grass and maize in the farm area and the way they are positioned in a rotation, and (iii) the susceptibility to leaching (i.e. the hydrological situation). The study also indicates that reductions of 50–60 kg and 25–30 kg slurry-N/ha per year are required in grassland and maize, respectively, if growing conditions or cropping management are suboptimal.

Chemical composition and fermentation characteristics of grain and different parts of the stover from maize land races harvested at different growing periods in two zones of central Mexico

AbstractThe objective of this work was to determine the rumen fermentation characteristics of maize land races used as forage in central Mexico. In vitro gas production (ml per 200 mg dry matter (DM)) incubations were carried out, and cumulative gas volumes were fitted to the Krishnamoorthyet al.(1991) model. The trial used a split-plot design with cultivation practices associated with maize colour (COL) as the main plot with three levels: white, yellow and black maize; growing periods (PER) were the split plots where PER1, PER2 and PER3 represented the first, second and third periods, respectively and two contrasting zones (Z1=valley and Z2=mountain) were used as blocking factors. The principal effects observed were associated with the maturity of the plants and potential gas production increased (P&lt;0·05) in stems (PER1=51·8, PER2=56·3, PER3=58·4 ml per 200 mg DM) and in whole plant (PER1=60·9, PER2=60·8, PER3=70·9 ml per 200 mg DM). An inverse effect was observed with fermentation rates in leaves (P&lt;0·01) with 0·061, 0·053 and 0·0509 (per h) and in whole plant (P&lt;0·05) with 0·068, 0·057, 0·050 (per h) in PER1, PER2 and PER3 respectively. The digestibility of the neutral-detergent fibre (NDF) decreased with maturity especially in leaves (P&lt;0·05) with values of 0·71, 0·67 and 0·66 g/kg; in rachis (P&lt;0·01) 0·75, 0·72, and 0·65 in PER1, PER2 and PER3 respectively. The NDF content in leaves in leaves (668, 705 and 713 g/kg DM for PER1, PER2 and PER3, respectively), stems (580, 594 and 644 g/kg DM) and, husk (663, 774 and, 808 g/kg DM) increased (P&lt;0·05) with increasing plant maturity, rachis were significantly different between periods (P&lt;0·01). The structure with the best nutritive characteristics was the husk, because it had the lowest fibre contents, especially in acid-detergent lignin, with values of 22·6, 28·6 and 37·6 g/kg DM in PER1, PER2 and PER3, respectively.

The effect of some herbicides on microbes and their activity in soil

Fertility of the soil is greatly influenced by the activity of soil-living microorganisms. Agricultural engineering (manuring, fertilising, cultivation, plant protection) directly or indirectly influences soil properties, thus affecting the activity of microbes of the soil. Taylor-Lovell et al. (2002) revealed that the degradation of isoxoflutol in the soil is accelerated by microbes. Angerer et al. (2004) studied the effects of new type herbicides on microbes in model experiments in which herbicides were used in doses as applied in agricultural practice and in higher doses. The results of these experiments show that microorganisms display different sensitivity to different doses of herbicides. Bird et al. (2002) showed that N-fixing bacteria are the most sensitive group in this sense. The results of experiments carried out on calcareous chernozem soil suggest that during the vegetation period the herbicide Acenit caused significant changes in the number and enzyme activity of soil-living microbes (K&tai, 1998). Katai et al. (2003) found that herbicides containing acetochloric-atrasin generally increased the number of bacteria and microscopic fungi and enhanced CO2 production. Experimental results about the other herbicides used in our investigation cannot be found in the literature. The aim of our study was to reveal the effects of herbicides used in maize lands on soil-living microorganisms and their activity.

The Cuiloni, the Patlache, and the Abominable Sin: Homosexualities in Early Colonial Nahua Society

The Cuiloni, the Patlache, and the Abominable Sin: Homosexualities in Early Colonial Nahua Society

Is political correctness damaging science?

Science is hardly unique in relying on peer review to determine merit and success. But for science, the reliance on peers to referee both submissions for publication and applications for grants involves greater dangers than in some other disciplines. It brings the triple risk of conformity, cronyism and plagiarism, which together can smother innovation. At a broader level, there is a tendency for researchers to fall in line with a particular point of view, especially in the more politically charged branches of science such as ecology or climatology. Those who oppose the prevailing orthodoxy risk being branded ‘flat earthers’ and cast into a wilderness where funding and publications are hard to obtain. According to Bruce Beutler, professor of immunology at the Scripps Research Institute (La Jolla, CA, USA), peer pressure in its various forms is a particular problem for science. “It is not unique to research, but in science it goes very much against the grain of what's trying to be accomplished,” he said. Yet scientists themselves must take some of the blame for perpetuating a system that can stifle original thinking, Beutler contends. “Scientists like to present an image to the outside world as being very iconoclastic and sceptical. Yet they have a complete conformity of opinion on certain things, and they do victimize people who differ from them.” By way of example, Beutler cited the atmosphere surrounding the recent US presidential election, in which any scientist who argued in favour of George W. Bush attracted severe ridicule. More worryingly though, such political correctness can distort research, with consequences not just for scientific direction but also for public matters such as health policy. “I think the best example of conformity of science is the influenza vaccine,” said Tom Jefferson, an independent researcher in the UK who specializes in immunology. …

Structural Adjustment Programme, Deforestation and Biodiversity Loss in Ghana

An empirical investigation is undertaken into the impact of the Structural Adjustment Programme (SAP) on forest and biodiversity loss in Ghana between the period 1965–1995. In the first part of the analysis, a four-equation recursive model, consisting of forest loss, cocoa land, maize land and timber production equations, is employed to examine the impact of the SAP on forest loss. The first equation is a function of the last three, and the last three are functions of mainly prices. Piecewise linear and switching regression approaches are used to distinguish between the influence of the post from the pre-adjustment impacts. These results together with a specie-forest area relationship are used to investigate the impact of the SAP on biodiversity loss. The overall results indicate that cocoa land expansion and timber production, but not maize land expansion, are the significant causes of forest loss in Ghana. However, the impact on forest loss in the post-adjustment period was reduced. The rate of biodiversity loss also reduced in the post-adjustment period. Changes in relative output and input prices due to the SAP may have played a significant role in the reduced impact of agricultural and timber related deforestation and biodiversity loss in the post-adjustment period.

Natural endophytic association between Rhizobium etli and maize ( Zea mays L.)

Maize ( Zea mays) and bean ( Phaseolus vulgaris) have been traditionally grown in association for thousands of years in Mesoamerica. From surface sterilized maize roots, we have isolated over 60 Rhizobium strains that correspond to Rhizobium etli bv. phaseoli (the main symbiont of bean) on the basis of 16S rRNA gene restriction patterns, metabolic enzyme electropherotypes, organization of nif genes, and the ability to nodulate beans. The colonization capacity of some of the isolates was tested with an unimproved maize cultivar and with 30 maize land races. Increases in plant dry weight upon R. etli inoculation were recorded with some of the land races, and these increases may be related to plant growth promotion effects. Additionally, from within maize grown in monoculture we have also recovered R. etli isolates recognizable by their 16S rRNA gene types, which lack nif genes and are incapable of nodulating bean. These strains are presumed to correspond to the earlier described non-symbiotic R. etli obtained from bean rhizosphere.