Influence Crop Yield Research Articles

Effects of elevated CO2and temperature on seed quality

Successful crop production depends initially on the availability of high-quality seed. By 2050 global climate change will have influenced crop yields, but will these changes affect seed quality? The present review examines the effects of elevated carbon dioxide (CO2) and temperature during seed production on three seed quality components: seed mass, germination and seed vigour. In response to elevated CO2, seed mass has been reported to both increase and decrease in C3 plants, but not change in C4 plants. Increases are greater in legumes than non-legumes, and there is considerable variation among species. Seed mass increases may result in a decrease of seed nitrogen (N) concentration in non-legumes. Increasing temperature may decrease seed mass because of an accelerated growth rate and reduced seed filling duration, but lower seed mass does not necessarily reduce seed germination or vigour. Like seed mass, reported seed germination responses to elevated CO2 have been variable. The reported changes in seed C/N ratio can decrease seed protein content which may eventually lead to reduced viability. Conversely, increased ethylene production may stimulate germination in some species. High-temperature stress before developing seeds reach physiological maturity (PM) can reduce germination by inhibiting the ability of the plant to supply the assimilates necessary to synthesize the storage compounds required for germination. Nothing is known concerning the effects of elevated CO2 on seed vigour. However, seed vigour can be reduced by high-temperature stress both before and after PM. High temperatures induce or increase the physiological deterioration of seeds. Limited evidence suggests that only short periods of high-temperature stress at critical seed development stages are required to reduce seed vigour, but further research is required. The predicted environmental changes will lead to losses of seed quality, particularly for seed vigour and possibly germination. The seed industry will need to consider management changes to minimize the risk of this occurring.

Ammonia volatilisation and crop yield following land application of solid–liquid separated, anaerobically digested, and soil injected animal slurry to winter wheat

To provide better advice to farmers and authorities on the most efficient way to reduce ammonia volatilisation from slurry applied to fields with standing crops, various treatments and injection methods were tested in field trials. In six separate experiments conducted at Research Centre Foulum, Denmark from 2007 to 2009, pig slurry was applied to winter wheat (Triticum aestivum L.) to determine how anaerobically digestion, solid–liquid separation of slurry and different soil injection techniques influence crop yield and ammonia emissions (NH3). The NH3 emission was measured by either a wind-tunnel method or by a micro-meteorological mass balance method. Both injection and solid–liquid separation were found to reduce NH3 emission. The emission from the separated slurry did not include the emission from the solid fraction. Most effective injection techniques were found to be a winged tine or a combination of discs and a tine, which reduced NH3 emission from approximately 20% (surface band spreading) to approximately 5% of applied Total Ammoniacal Nitrogen (TAN). The NH3 emission from surface-applied anaerobically digested slurry was found to be almost twice that from surface-applied untreated slurry.Injection did not affect yields significantly compared with surface application in any of the experiments, but did result in a significantly increased protein content in grains compared to band application, which increased the nitrogen utilisation of slurry nitrogen. Of the techniques tested, soil injection and solid–liquid separation reduced NH3 emissions most effectively.

Production and quality of melon hybrid Mandacaru irrigated with different levels of salinity

Among the problems faced by the melon crop in the state of Rio Grande do Norte, northeastern Brazil, the effect of water and soil salinity is considered one of the key factors to limit fruit production and quality. The aim of this work was to study the effects of using irrigation waters with different salinity levels on yield and quality of fruits of the yellow melon hybrid Mandacaru. A randomized complete block design was used with five treatments (irrigation water salt concentrations: 0.54, 1.48, 2.02, 3.03, 3.9 dS m-1) and four replications. The effects of these concentrations were evaluated through, number of marketable fruits per plant, marketable and total fruit yield, average marketable fruit mass, soluble solids content and pulp firmness. Increment in water salinity level negatively influenced crop yield. The 3.9 dS m-1 salinity level caused yield losses of 20.31%, due to the reduction of fruit number per plant. The highest soluble solid content and the highest pulp firmness values were estimated to occur at salinity levels 2.09 and 3.5 dS m-1, respectively.

Fertilizer Best Management Practices: A Perspective from the Dryland West Asia–North Africa Region

AbstractChemical fertilizer use has contributed significantly to increased global food output in the past half century, especially in climatically favourable regions of the world. However, in drier agro‐ecological zones, such as in West Asia and North Africa (WANA) with a Mediterranean‐type climate, fertilizer use has been low but has increased rapidly in the past few decades. Chemical fertilizer use is now widely adopted in rainfed and irrigated agriculture. As elsewhere, fertilizer use is underpinned by concerns about biological and economic efficiency. Fertilizer use efficiency is central to the current concept of fertilizer best management practices (FBMP), which embraces right source, right place, right timing and right application method. In this brief review, we highlight such FBMP concepts as related to agriculture of the WANA region, with emphasis on the key nutrients for crop production. Rainfall has a dominant influence on dryland crop yields. Nitrogen (N) use efficiency increases with increasing rainfall and is influenced by crop rotation. Under rainfed conditions, modest N losses by volatilization can occur. Leaching losses are usually minimal. Phosphorus use (P) efficiency is higher with band application than with broadcasting. Balanced fertilization, especially involving potassium (K) and micronutrients, is fundamental to efficient nutrient use. Fertilizer efficiency is also influenced by soil test values and agronomic factors that influence crop yields, e.g. sowing date and varietal differences. Rational fertilizer application rates are guided by calibration–response trials. Effective fertilizer use in the region is also dictated by external factors such as government policies and a functioning extension service. In contrast to other regions of the world, environmental impacts from the overuse of fertilizers are relatively minor, while developments in fertilizer formulations that promote efficiency have yet to have impact. Despite the relatively low fertilizer use intensity in dryland areas such as the WANA region, the FBMP comprehensive approach is a logical framework within which to achieve the most efficient management and use of fertilizer in the region’s agriculture.

A meta-analysis of long-term effects of conservation agriculture on maize grain yield under rain-fed conditions

Conservation agriculture involves reduced tillage, permanent soil cover and crop rotations to enhance soil fertility and to supply food from a dwindling land resource. Recently, conservation agriculture has been promoted in Southern Africa, mainly for maize-based farming systems. However, maize yields under rain-fed conditions are often variable. There is therefore a need to identify factors that influence crop yield under conservation agriculture and rain-fed conditions. Here, we studied maize grain yield data from experiments lasting 5 years and more under rain-fed conditions. We assessed the effect of long-term tillage and residue retention on maize grain yield under contrasting soil textures, nitrogen input and climate. Yield variability was measured by stability analysis. Our results show an increase in maize yield over time with conservation agriculture practices that include rotation and high input use in low rainfall areas. But we observed no difference in system stability under those conditions. We observed a strong relationship between maize grain yield and annual rainfall. Our meta-analysis gave the following findings: (1) 92% of the data show that mulch cover in high rainfall areas leads to lower yields due to waterlogging; (2) 85% of data show that soil texture is important in the temporal development of conservation agriculture effects, improved yields are likely on well-drained soils; (3) 73% of the data show that conservation agriculture practices require high inputs especially N for improved yield; (4) 63% of data show that increased yields are obtained with rotation but calculations often do not include the variations in rainfall within and between seasons; (5) 56% of the data show that reduced tillage with no mulch cover leads to lower yields in semi-arid areas; and (6) when adequate fertiliser is available, rainfall is the most important determinant of yield in southern Africa. It is clear from our results that conservation agriculture needs to be targeted and adapted to specific biophysical conditions for improved impact.

Producción y distribución de materia seca en lerén [Calathea allouia (Aubl.) Lindl

El lerén [Calathea allouia (Aubl.) Lindl] es un tubérculo tropical con potencial para procesamiento y como un sustituto para las castañas de agua. La sombra afecta la tasa fotosintética del cultivo por lo que el crecimiento y los rendimientos varían. Existe poca información en cuanto al mejoramiento agronómico de este cultivo. Este estudio se estableció para entender cómo, a través de la manipulación de la luz, densidad poblacional y factores nutricionales, la producción y distribución de los asimilatos afecta el rendimiento del cultivo. Al igual que para determinar si los rizomas del lerén son los verdaderos sumideros o si actúan como un filtro/almacenamiento para la tuberización. Se llevaron a cabo varios experimentos de invernadero y de campo durante un periodo de dos años en la Estación de Campo de la Universidad de Trinidad Tobago. Los tratamientos evaluados fueron luz [luz solar completa y sombra (50%)], densidad poblacional (20.8 y 27.7 mil plantas por hectárea), y fertilización [N-P2-O5-K2O (13:13:20)]a varios niveles (0.0 a 0.6 t/ha). Se midió el área foliar, materia seca, y rendimiento de los tubérculos. Los resultados indicaron que el índice de área foliar varió entre 1.38 (luz solar) y 3.08 (sombra) y que el mismo no estuvo afectado por la nutrición del cultivo. Tanto para los ensayos de invernadero como los de campo, la acumulación de material seca en los rizomas y su distribución en los tubérculos fue mayor en los tratamientos con sombra que en aquellos bajo luz solar. La aplicación de fertilizantes no influenció el crecimiento de las hojas ni la producción de materia seca (capacidad fotosintética) en los ensayos en el invernadero, pero hubo mayor distribución de asimilatos desde los rizomas hasta los tubérculos cuando se usó una menor densidad poblacional x intercalado. La distribución de asimilatos de los tallos a los rizomas, y de los rizomas a los tubérculos fue más eficiente en los tratamientos de sombra x intercalado. La aplicación de fertilizante a la dosis de 0.5 t/ha a la densidad de 20.8 mil plantas por hectárea produjo la mayor cantidad de materia seca (1,066 g/planta) y el mayor rendimiento de tubérculos (261.3 g/planta). El estudio sugiere que en el lerén, los rizomas y tubérculos son los sumideros primarios y secundarios, respectivamente, con una distribución de asimilatos de tallos a rizomas y de rizomas a tubérculos.

Global growth and stability of agricultural yield decrease with pollinator dependence

Human welfare depends on the amount and stability of agricultural production, as determined by crop yield and cultivated area. Yield increases asymptotically with the resources provided by farmers' inputs and environmentally sensitive ecosystem services. Declining yield growth with increased inputs prompts conversion of more land to cultivation, but at the risk of eroding ecosystem services. To explore the interdependence of agricultural production and its stability on ecosystem services, we present and test a general graphical model, based on Jensen's inequality, of yield-resource relations and consider implications for land conversion. For the case of animal pollination as a resource influencing crop yield, this model predicts that incomplete and variable pollen delivery reduces yield mean and stability (inverse of variability) more for crops with greater dependence on pollinators. Data collected by the Food and Agriculture Organization of the United Nations during 1961-2008 support these predictions. Specifically, crops with greater pollinator dependence had lower mean and stability in relative yield and yield growth, despite global yield increases for most crops. Lower yield growth was compensated by increased land cultivation to enhance production of pollinator-dependent crops. Area stability also decreased with pollinator dependence, as it correlated positively with yield stability among crops. These results reveal that pollen limitation hinders yield growth of pollinator-dependent crops, decreasing temporal stability of global agricultural production, while promoting compensatory land conversion to agriculture. Although we examined crop pollination, our model applies to other ecosystem services for which the benefits to human welfare decelerate as the maximum is approached.

Functional mapping of quantitative trait loci associated with rice tillering

Several biologically significant parameters that are related to rice tillering are closely associated with rice grain yield. Although identification of the genes that control rice tillering and therefore influence crop yield would be valuable for rice production management and genetic improvement, these genes remain largely unidentified. In this study, we carried out functional mapping of quantitative trait loci (QTLs) for rice tillering in 129 doubled haploid lines, which were derived from a cross between IR64 and Azucena. We measured the average number of tillers in each plot at seven developmental stages and fit the growth trajectory of rice tillering with the Wang-Lan-Ding mathematical model. Four biologically meaningful parameters in this model--the potential maximum for tiller number (K), the optimum tiller time (t(0)), and the increased rate (r), or the reduced rate (c) at the time of deviation from t(0)--were our defined variables for multi-marker joint analysis under the framework of penalized maximum likelihood, as well as composite interval mapping. We detected a total of 27 QTLs that accounted for 2.49-8.54% of the total phenotypic variance. Nine common QTLs across multi-marker joint analysis and composite interval mapping showed high stability, while one QTL was environment-specific and three were epistatic. We also identified several genomic segments that are associated with multiple traits. Our results describe the genetic basis of rice tiller development, enable further marker-assisted selection in rice cultivar development, and provide useful information for rice production management.

Determination of the effect of precipitation distribution on yield of wheat and pea in dryland using APSIM

By using APSIM model, the effect of precipitation seasonal distribution on crop yield was determined in rain-fed agriculture area of the Loess Plateau. Next, the effect of precipitation seasonality on crop yield was explored via integral regression analysis. The study shows that APSIM model can reliably simulate wheat and pea yield. Crop yield is highly related with annual precipitation and its seasonal distributon. The seasonal distribution of participation has a positive U-shaped quadratic relation with wheat and pea yield. Precipitation in the months of June and July significantly influences wheat yield, while that in the months of May and June importantly influences pea yield. With 1 mm increase in precipitation, wheat and pea yield respectively increases at the rate of 10.4 kg·hm-2 and 10.3 kg·hm-2. Seasonal precipitation distribution more importantly influences crop yield than annual precipitation.

Relationship between Rice Yield and Apparent Electrical Conductivity of Paddy Soils

Problem statement: Understanding the relationships between rice yield and soil properties such as bulk electrical conductivity is of critical importance in precision farming. The apparent Electrical Conductivity of soil (ECa) is influenced by a combination of physico-chemical properties including soluble salts, clay content and mineralogy, soil water content, bulk density, organic matter and soil temperature. Accordingly, ECa is considered as the most reliable and frequently used tools in precision farming research for the spatio-temporal characterization of edaphic and anthropogenic properties that influence crop yield. Many researchers have found positive correlation of ECa to crop yield such as corn and soy bean but not rice paddies. This study discussed on the relationship between ECa and rice yield for best practice management on paddy field. Approach: The analyses had used two reliable methods in six selected paddy lots at Sawah Sempadan, Selangor, Malaysia. Stepwise Linear Regression (SLR) and Boundary Line Analysis (BLA) techniques were used. External factors such as weather conditions, disease outbreaks, labor shortage and other factors were not considered in the data analysis and interpretation. Results: The results indicate that deep ECa (ECad) is significantly related to rice yield with R 2 = 0.1246 and R 2 = 0.4156 from SLR and BLA analyses, respectively. Conclusion: Results of this study can benefit farmers and researchers to understand the influence of ECa to the crop productivity.

Inverse Solution of Soil-Water Transport Model Parameters Using Response Surface Methodology

<emph italic=no/>Soil hydraulic properties influence crop yield, soil fertility, and soil water status. While the laboratory or direct methods of measuring hydraulic properties are accurate, they are expensive, time consuming, and may not represent in-situ properties. On the other hand, model-based inverse solution procedures or indirect methods of estimating soil hydraulic conductivity (K) relate primary model variables such as volumetric water content (<emph>θ</emph>) and soil water suction (<emph>ψ</emph>) to K and the soil-water characteristic curve. In this study, an inverse solution technique was developed to determine saturated soil hydraulic conductivity (K<emph subscript=yes>s</emph>, cm h<emph superscript=yes>-1</emph>) and plant conductance to water uptake (C, m<emph superscript=yes>-1</emph> min<emph superscript=yes>-1</emph>) under field conditions using a 1-D water transport model. The soil water content data (<emph>θ</emph>) were measured at 12 locations and at several depths at each location within the root zone in two different alfalfa checks using access tubes (each 1.5 m deep) and a neutron moisture probe. The inverse solution process utilized the measured soil moisture conditions in the alfalfa checks between two successive irrigations. In this study, the soil water retention curve was assumed to be of the form described by van Genuchten. The water contents at upper (0.225 m) and lower (1.2 m) depths provided the boundary conditions (BCs) needed for the model. The water content readings immediately following the irrigation event (i.e., t = 0) were used as the initial condition (IC). The model was solved to develop third-order orthogonal response surfaces over a range of model parameters (K<emph subscript=yes>s</emph> and C). Moreover, a multiple linear regression technique was used to empirically relate experimental <emph>θ</emph> to the depth and time of measurements. The response surface solutions were then optimized against the empirical surface to seek the optimum values of K<emph subscript=yes>s</emph> and C. The parameters estimated by the inverse solution technique were found to be unique and robust, and they predicted experimentally observed soil water data very well (R<emph superscript=yes>2</emph> > 0.95 and slope = 1:1 for most of the cases). These parameters, known from the inverse solution technique, were used to estimate the amount of deep percolation beyond the root zone depth for all cases.

Compost, Manure and Synthetic Fertilizer Influences Crop Yields, Soil Properties, Nitrate Leaching and Crop Nutrient Content

From 1993 to 2001, a maize-vegetable-wheat rotation was compared using either 1) composts, 2) manure, or 3) synthetic fertilizer for nitrogen nutrient input. From 1993 to 1998, red clover (Trifolium pratense L.) and crimson clover (Trifolium incarnatum L.) were used as an annual winter legume cover crop prior to maize production. From 1999 to 2001, hairy vetch (Vicia villosa Roth.) served as the legume green manure nitrogen (N) source for maize. In this rotation, wheat depended entirely on residual N that remained in the soil after maize and vegetable (pepper and potato) production. Vegetables received either compost, manure, or fertilizer N inputs. Raw dairy manure stimulated the highest overall maize yields of 7,395 kg/ha (approximately 140 bushels per acre). This exceeded the Berks County mean yield of about 107 bushels per acre from 1994 to 2001. When hairy vetch replaced clover as the winter green manure cover crop, maize yields rose in three of the four treatments (approximately 500-1,300 kg/ha, or 10-24 bu/a). Hairy vetch cover cropping also resulted in a 9-25 % increase in wheat yields in the compost treatments compared to clover cover cropping. Hairy vetch cover crops increased both maize and wheat grain protein contents about 16 to 20% compared to the clover cover crop. Compost was superior to conventional synthetic fertilizer and raw dairy manure in 1) building soil nutrient levels, 2) providing residual nutrient support to wheat production, and 3) reducing nutrient losses to ground and surface waters. After 9 years, soil carbon (C) and soil N remained unchanged or declined slightly in the synthetic fertilizer treatment, but increased with use of compost amendments by 16-27% for C and by 13-16% for N. However, with hairy vetch cover crops, N leaching increased 4 times when compared to clover cover crops. September was the highest month for nitrate leaching, combining high rainfall with a lack of active cash crop or cover crop growth to use residual N. Broiler litter leaf compost (BLLC) showed the lowest nitrate leaching of all the nutrient amendments tested (P= 0.05).

Application of Two Microbial Teas Did Not Affect Collard or Spinach Yield

Microbial tea from a commercial source and a homemade manure tea were evaluated for 2 years under organic and conventional fertility regimens. Testing with different fertility regimens allowed broader assessment of tea efficacy. Collard green (Brassica oleracea L. var. acephala cv. Top Bunch) yield and soil microbial activity were measured after microbial tea applications were made in three fertility treatments (conventional, organic, or no fertilizer amendment) on a previously unfertilized sandy loam soil. Spinach (Spinacia oleracea L. cv. Hellcat) and collard green yields were determined after commercial microbial tea application to a silt loam soil previously managed with organic or conventional vegetable crops in open fields and under high tunnels. Results indicated that nutrient additions influenced crop yields, even doubling yield. This demonstrated that improved nutrient availability would affect yield at the chosen locations. However, microbial tea applications did not affect crop yield. These results did not support the hypothesis that microbial tea improves plant nutrient uptake. Additionally, soil microbial respiration and biomass were unaffected after two or three tea applications.

Early-Season Aerial Adult Colonization and Ground Activity of Pea Leaf Weevil (Coleoptera: Curculionidae) in Pea as Influenced by Tillage System

The pea leaf weevil, Sitona lineatus (L.) (Coleoptera: Curculionidae), is an important pest of pea, Pisum sativum L., in northern Idaho. Previous research revealed greater relative pea leaf weevil abundance and feeding damage in peas grown using conventional-tillage compared with no-tillage practices. However, the effects of tillage practices on early season colonization and activity by the pea leaf weevil on pea are not fully understood. Aerial traps and pitfall traps were used to assess adult colonization and relative density of adult pea leaf weevil into conventional-tillage and no-tillage pea in northern Idaho during 2005 and 2006. Feeding damage to the crop also was evaluated. During both years, aerial traps captured more pea leaf weevil in May, when crop establishment and early growth occurred, than in later months. Significantly more adult pea leaf weevils were captured in aerial traps in conventional-tillage than in no-tillage plots in May of both years. Significantly more pea leaf weevil were captured in pitfall traps in conventional-tillage plots than in no-tillage plots during the period immediately after peak aerial adult colonization in late May and early June. Crop feeding damage was significantly greater in conventional-tillage than in no-tillage plots in late May and early June. The patterns suggest that more adult pea leaf weevil colonize conventional-tillage pea than no-tillage pea. Pea plants in conventional-tillage emerged earlier and were larger than those in no-tillage during the pea leaf weevil colonization period, possibly accounting for the differences in colonization rates. This leads to greater early season pea leaf weevil infestation of conventional-tillage plots at a critical period for pea development that might ultimately influence crop yield.

Early-season aerial adult colonization and ground activity of pea leaf weevil (Coleoptera: Curculionidae) in pea as influenced by tillage system.

The pea leaf weevil, Sitona lineatus (L.) (Coleoptera: Curculionidae), is an important pest of pea, Pisum sativum L., in northern Idaho. Previous research revealed greater relative pea leaf weevil abundance and feeding damage in peas grown using conventional-tillage compared with no-tillage practices. However, the effects of tillage practices on early season colonization and activity by the pea leaf weevil on pea are not fully understood. Aerial traps and pitfall traps were used to assess adult colonization and relative density of adult pea leaf weevil into conventional-tillage and no-tillage pea in northern Idaho during 2005 and 2006. Feeding damage to the crop also was evaluated. During both years, aerial traps captured more pea leaf weevil in May, when crop establishment and early growth occurred, than in later months. Significantly more adult pea leaf weevils were captured in aerial traps in conventional-tillage than in no-tillage plots in May of both years. Significantly more pea leaf weevil were captured in pitfall traps in conventional-tillage plots than in no-tillage plots during the period immediately after peak aerial adult colonization in late May and early June. Crop feeding damage was significantly greater in conventional-tillage than in no-tillage plots in late May and early June. The patterns suggest that more adult pea leaf weevil colonize conventional-tillage pea than no-tillage pea. Pea plants in conventional-tillage emerged earlier and were larger than those in no-tillage during the pea leaf weevil colonization period, possibly accounting for the differences in colonization rates. This leads to greater early season pea leaf weevil infestation of conventional-tillage plots at a critical period for pea development that might ultimately influence crop yield.

Natural genetic variation in acclimation capacity at sub-zero temperatures after cold acclimation at 4 °C in different Arabidopsis thaliana accessions

Freezing tolerance is an important factor in the geographical distribution of plants and strongly influences crop yield. Many plants increase their freezing tolerance during exposure to low, nonfreezing temperatures (cold acclimation) and acclimation may continue at mild freezing temperatures in a process termed sub-zero acclimation. There is considerable natural variation in the cold acclimation capacity of Arabidopsis that has been used to study the molecular basis of this trait, but much less is known about the molecular basis of sub-zero acclimation. Freezing tolerance of detached leaves from the accessions C24, Columbia-0, Rschew, and Tenela was investigated using an electrolyte leakage assay. Sub-zero acclimation could be achieved by shifting plants from 4 °C to −3 °C, or by using detached leaves, either in the presence or absence of ice nucleation. The magnitude of the increase in freezing tolerance depended on both temperature and duration of sub-zero acclimation and while Columbia-0 showed no significant increase in freezing tolerance, the other three accessions increased their freezing tolerance significantly. The levels of several sugars that have been shown to be induced during cold acclimation at nonfreezing temperatures were not strongly changed during sub-zero acclimation and there was no correlation between the increases in freezing tolerance and sugar levels in the different accessions. Expression of the three cold induced CBF transcription factor genes and five of their representative target COR genes was moderately increased during sub-zero acclimation, but again there was no correlation to changes in freezing tolerance, indicating that the genetic and molecular basis of sub-zero acclimation is most likely different from that of cold acclimation at above freezing temperatures. Further studies will be needed to reveal novel signal transduction pathways and protective mechanisms important in sub-zero acclimation.

Chlorophyll fluorescence imaging accurately quantifies freezing damage and cold acclimation responses in Arabidopsis leaves

BackgroundFreezing tolerance is an important factor in the geographical distribution of plants and strongly influences crop yield. Many plants increase their freezing tolerance during exposure to low, nonfreezing temperatures in a process termed cold acclimation. There is considerable natural variation in the cold acclimation capacity of Arabidopsis that has been used to study the molecular basis of this trait. Accurate methods for the quantitation of freezing damage in leaves that include spatial information about the distribution of damage and the possibility to screen large populations of plants are necessary, but currently not available. In addition, currently used standard methods such as electrolyte leakage assays are very laborious and therefore not easily applicable for large-scale screening purposes.ResultsWe have performed freezing experiments with the Arabidopsis accessions C24 and Tenela, which differ strongly in their freezing tolerance, both before and after cold acclimation. Freezing tolerance of detached leaves was investigated using the well established electrolyte leakage assay as a reference. Chlorophyll fluorescence imaging was used as an alternative method that provides spatial resolution of freezing damage over the leaf area. With both methods, LT50 values (i.e. temperature where 50% damage occurred) could be derived as quantitative measures of leaf freezing tolerance. Both methods revealed the expected differences between acclimated and nonacclimated plants and between the two accessions and LT50 values were tightly correlated. However, electrolyte leakage assays consistently yielded higher LT50 values than chlorophyll fluorescence imaging. This was to a large part due to the incubation of leaves for electrolyte leakage measurements in distilled water, which apparently led to secondary damage, while this pre-incubation was not necessary for the chlorophyll fluorescence measurements.ConclusionChlorophyll fluorescence imaging is an alternative method to accurately determine the freezing tolerance of leaves. It is quick and inexpensive and the system could potentially be used for large scale screening, allowing new approaches to elucidate the molecular basis of plant freezing tolerance.

Processo de semeadura e o rendimento do milho na região dos Campos Gerais do Paraná

Na região dos Campos Gerais (PR), a cultura do milho ocupa aproximadamente um terço das áreas sob plantio direto no verão. Visando a manejos diferenciados, faz-se necessário conhecer as variáveis que influenciam no rendimento do milho. Este trabalho teve como objetivo correlacionar variáveis químicas e físicas de solo e antrópicas com a resposta da cultura do milho, considerando-se variabilidade espacial regional. As variáveis antrópicas estudadas foram: pressão de população, índice de pressão populacional, profundidade de semeadura e desvio padrão da profundidade de semeadura. As variáveis de solo estudadas foram: profundidade do horizonte A, areia, silte, argila, matéria orgânica, pH, boro e manganês para a profundidade de 0-20cm, e areia, silte, argila, matéria orgânica, manganês e cobre para a profundidade 20-40cm. Para representar o rendimento da cultura, a variável resposta avaliada foi a massa de grãos da espiga por planta. Para redução do número de variáveis, utilizaram-se os métodos estatísticos de redução de variáveis explicativas "Todas Regressões Possíveis" (Best subsets) e "Passo-a-Passo" (Stepwise). As variáveis de solo reafirmaram-se como importantes para explicar o fenômeno massa de grãos. A variável antrópica profundidade de semeadura mostrou-se explicativa para o fenômeno estudado, demonstrando a influência do processo de semeadura no rendimento do milho.

Gains and losses induced by agrochemical applications

Agrochemical applications are essential technological means in growing field crops. The most critical technological points in production of grain crops are agrochemical interventions, so that it is essential to reveal and study soundly their impacts (AgostonPepo, 2005; Czovek et al., 2006). Chemical applications are seen by the public to be both harmful to crops and environment, however appropriate treatments are securing high yields and help to reduce serious weed infestations in our ecosystems (Hegedős et al., 2002; Jolankai, 2005; Szentpetery et al., 2005 a and b; Tanacs et al. a and b). The aim of our tial was to evaluate the effects of ascending nitrogen applications as well as to study how plant protection treatments can influence crop yield and weed infestation of wheat crop. In this paper results of the effect of N fertilizer and pesticide applications on grain yield of winter wheat are presented from a single year (2006) of a long term trial study. Results of the previous years was published by Kismanyoky (2005).

Impacts of climate change and CO2 increase on agricultural production and adaptation options for Southern Québec, Canada

This study involves the assessment of the potential impacts of greenhouse gas climate change and changing ambient carbon dioxide (CO2) levels on crop yields in Quebec, Canada. The methodology involves coupling the transient diagnostics of two Atmosphere-Ocean General Circulation Models, namely the Canadian CGCM1 and the British HadCM3, to the Decision Support System for Agrotechnology Transfer (DSSAT) 3.5 crop models to simulate current (1961–1990) and future (2040–2069) crop yields and changes. This is done for four different crop species, namely spring wheat, maize, soybean, and potato, and for seven agricultural regions of Southern Quebec. The results of this study focus on the main causative factors influencing crop yields, namely the direct CO2 fertilization effect, the influence of the increase in growing season temperature, including optimal thermal conditions and acceleration in crop maturation, soil moisture availability, as influenced by precipitation and evapotranspiration, and nitrogen uptake by crops. Our results show that crop yield changes may vary according to climate scenario, crop species, and agricultural region. Consistent with other similar research, it would seem that these multiple causative factors very often seem to cancel each other out and dilute the impacts of climate change on crop yields.