Annual Field Crops Research Articles

Root growth dynamics and biomass input by Nordic annual field crops

Roots are an important sink for photoassimilates and carbon input to soil. Here the root growth and biomass of different spring sown annuals was determined to estimate the shoot:root (S:R) ratios and carbon inputs in the typical Nordic agroecosystem. The data, collected in southern Finland, present evidence for large difference in root growth dynamics and biomass input between spring oilseed rape ( Brassica rapa L. ) and annual ryegrass ( Lolium multiflorum Lam. var . italicum ) whereas the rooting of spring sown barley ( Hordeum vulgare ) and oats ( Avena sativa ) was related. The four crops were sown at the same time in a field with a fine sand soil (Eutric Cambisol) with good nutrient and water supply. During one growing season, root growth was determined 12 times to a soil depth of 50 cm by using a minirhizotron-micro-video camera technology. At anthesis, root biomass and morphological parameters were measured to 60 cm soil depth at 5 cm intervals, with destructive soil sampling and image analysis of washed roots. The root growth rate of oilseed rape was clearly faster and that of rye grass slower compared with the other crops. At anthesis, the average total root dry biomass (0–60 cm) was160 g for barley, 260 g for oats, 340 g for ryegrass, and 110 g m −3 for oilseed rape. Also, the root length density and surface area of oilseed rape was less than that of other crops. Most of the biomass (59–80%) was accumulated the upper 20 cm of the soil. Shoot to root ratios (at anthesis for the seed crops) of 7.1, 4.4, 4.2 and 2.5 for barley, oats, oilseed rape, and ryegrass respectively, could be used for an approximation to estimate the amount of root biomass left in the 0–60 cm soil layer under Nordic long day conditions. In contrast to the seed crops, the root growth rate and density of ryegrass was high in the late season. Thus, ryegrass would be an efficient catch crop after harvest of cereals.

Daily Simulation of Potential Dry Matter Production of Annual Field Crops in Tropical Environments

This paper describes the modeling procedures activated when assessing potential biomass production using the Daily Crop Growth Simulator (DAICROS). Under optimal water and nutrient supply, the main physiological processes governing crop growth are photosynthesis, respiration, and leaf expansion. Simulation of the gross photosynthesis rate involves, among others, assessment of the maximum photosynthesis rate at light saturation, description of the photosynthesis light response of a fully developed canopy, and simulation of the leaf area index (LAI). Within the respiration module, maintenance respiration losses are quantified together with the conversion efficiency of the net primary assimilates into crop dry matter (DM), reflecting growth respiration losses. Leaf growth is simulated using a simplified model based on the LAI at maximum growth rate and the characterization of four leaf growth stages including fast linear growth during the vegetative stage and exponential decay at the end of the crop cycle. Input requirements include daily records of temperature and sunshine duration and crop parameters to be provided by local experts or the international literature. Both input requirements and output returns are illustrated by a case study simulating potential DM production of common bean (Phaseolus vulgaris L.) in Kigali, Rwanda. Sensitivity analysis and comparison of the simulated potential yields of five annual crops with field, literature, and alternative crop growth model outputs proved successful for model validation in the tropics and subtropics. Modeling capacity, functionality, and expendability of DAICROS surpass the performance of the worldwide operational crop growth model for land evaluation purposes developed by Tang.

Aridity and the Potential Physiological Response of C 3 Crops to Doubled Atmospheric Co 2 : A Simple Demonstration of the Sensitivity of the Canadian Prairies

Since cultivated annual C3 field crops cover about50% of the land surface of the Canadian Prairie grassland eco-climatic zone, this vegetationinfluences the aridity of the climate during the growing season. The physiological response of these cropsto a doubling of the atmospheric concentration of CO2 may be a doubling of canopyresistance. If this physiological effect is not counteracted by interactive feedbacks, such as increasedleaf area, evapotranspiration rates could be reduced. To demonstrate the sensitivity of thearidity of the Prairie climate to this potential physiological effect, representative spring wheatgrowing-season soil moisture and Bowen ratio curves for a doubled canopy resistance(2 × CO2) scenario were compared with a control (1 × CO2) scenario.Lower evapotranspiration in the 2 × CO2 scenario: (1) Increased root-zone soilmoisture levels, and (2) weakened the atmospheric component of the hydrologic cycle by raisingBowen ratios, which reduces the convective available energy, and reduces the regionalcontribution to the atmospheric water vapour over the Prairies. A weakened hydrologic cycleimplies less rainfall, and possibly, lower soil moisture levels. Thus, the net impact of a doublingof the atmospheric concentration of CO2 on the aridity of the Canadian Prairies is uncertain.This simple sensitivity demonstration did not consider most of the potential feedback mechanisms,nor interactions of other processes. Nevertheless, the result illustrates that the physiologicaleffect should be explicitly included in climate change models for the Canadian Prairies.

Towards the on‐farm conservation of the assassin bug Pristhesancus plagipennis (Walker) (Hemiptera: Reduviidae) during winter using crop plants as refuges

Abstract Habitat instability associated with seasonal crop succession in broad‐acre farming systems presents a problem for the conservation and utilisation of beneficial insects in annual field crops. The present paper describes two experiments used to measure the potential of seven plant species to be utilised as winter refuges to support and conserve the predatory bug Pristhesancus plagipennis (Walker). In the first experiment, replicated plots of canola (Brassica napus), red salvia (Salvia coccinea), niger (Guizotia abyssinica), linseed (Linum usitatissimum), lupins (Lupinus angustifolius), and lucerne (Medicago falcata) were planted in a randomized experiment during Autumn 1998. Upon crop establishment, adults and nymphs of P. plagipennis were released into treatment plots and their numbers were assessed, along with those of their potential prey, throughout the ensuing winter months. Post‐release sampling suggested that canola and niger retained a proportion of adult P. plagipennis, while niger, lucerne and canola retained some nymphs. The other plant species failed to support P. plagipennis nymphs and adults postrelease. In the second experiment, niger was compared with two lines of sunflower (Helianthus annus). Both sunflower lines harboured significantly higher (P < 0.05) densities of P. plagipennis nymphs than did niger. The more successful refuge treatments (sunflower, niger and canola) had an abundance of yellow flowers that were attractive to pollinating insects, which served as supplementary prey on which P. plagipennis were observed to feed. Sunflower and niger also supported high densities of the prey insect Creontiades dilutus (Stål) and provided protective leafy canopies which supplied shelter during the winter months. The potential and limitations for using each plant species as a winter refuge to retain P. plagipennis during winter are discussed.

Agriculture and Tornadoes on the Canadian Prairies: potential impact of increasing atmospheric CO2 on summer severe weather

On the Canadian Prairies, a significantportion of the transpiration is derived from a ratherhomogenous agro-ecosystem comprised of springwheat and other annual C3 field crops with similar water use patterns. The seasonal pattern oftranspiration is determined, to alarge extent, by crop phenology. By increasing thespecific humidity of the atmospheric boundarylayer, regional transpiration has a large positive effect on themagnitude of the potential energy available fordeep convection and thus, on the likelihood of occurrence andintensity of severe thunderstorms. Acomparison of the average wheat phenologycurve, for a representative aridgrassland and for a representativetransitional grassland site, with theaverage number of tornado days per week inthe entire eco-climatic zone demonstrated that the twoare linked. With increasing atmospheric concentrations ofCO2, the physiological response of C3 cropsmight lower transpiration rates and climate warming may advance cropseeding dates. The former would reduce the specifichumidity of the convective boundary layer, and thereby, reducethe potential energy available for deep convection.Thus, future summer severe weather seasons might, on average,be more benign and occur earlier in the seasonthan at present. This conclusion is far from certain as there are amultitude of complex feedback mechanisms. What ismore certain is that global circulation models (GCMs) mustadequately handle the inter-action between theatmosphere and the agro-ecosystem of the Canadian Prairies beforethey can correctly simulate the thermodynamic propertiesof the convective boundary layer and determine the impactof increasing atmospheric concentrations of CO2 onfuture summer severe weather.

Glucosinolate genetics and the attraction of the aphid parasitoid Diaeretiella rapae to Brassica.

The control of insect pests using parasitoids and carnivores has been successfully applied in protected cropping systems, orchards and forestry. Their success in annual field crops has been more limited due largely to the difficulties of attracting and maintaining a sufficient density of parasitoids in the crop before the levls of the insect herbivores become economically damaging. Parasitoids are known to be attracted to host-plant volatiles; thus, manipulating the host-plant chemistry may provide a means of enhancing the attraction of parasitoids to their prey. In this study we describe the differential attraction of the braconid wasp Diaeretiella rapae to two near-isogenic lines of Brassica oleracea which differ in a gene which alters the chemical structure of the isothiocyanates which are emitted following tissue damage. We demonstrate that, by enhancing the production of but-3-enyl isothiocyanate in B. oleracea and Brassica napus (oilseed rape), we can increase the attraction of D. rapae to these plants under standard field conditions.

Anthropogenic vegetation transformation and the potential for deep convection on the Canadian prairies

Widespread agricultural cultivation has converted nearly 60% of the Canadian Prairie grasslands eco-climatic zone from native mixed perennial grasses to annual field crops, predominantly spring wheat. This study examined the effect this anthropogenic landscape transformation has had on the partitioning of latent and sensible heat. For each type of vegetation, a representative growing-season Bowen ratio curve, based on modelled evapotranspiration values, was determined for sample sites — Winnipeg, MB, in the transitional grassland, and Swift Current, SK, in the arid grassland. A relationship between the Bowen ratio, the noon global radiation and the change in the Lifted Index between morning and afternoon was used to asses how modifying the apportionment of surface heat flux may have changed the seasonal frequency and severity of thunderstorms. Prior to the emergence of annual crops, and again during their senescence and in the post-harvest period, Bowen ratios are generally higher (i.e., evapotranspiration rates are lower) than they would be if the Prairie grassland eco-climatic zone had remained a sea of perennial grasses. Thus, the available buoyant energy or the potential for deep convection has been reduced in these periods. Given similar atmospheric dynamic forcing and advection patterns, this change has likely reduced the frequency of thunderstorms during the early and the late portions of the growing season. In contrast, during rapid foliage expansion and seed production for spring wheat, and for similar annual field crops, Bowen ratios are generally lower (i.e., evapotranspiration rates are higher) than they would be without agriculture. Thus, the potential for deep convection has been enhanced in these periods. With similar dynamic and advection patterns, it is probable that thunderstorms are now more frequent in the middle of the growing season and increased available buoyant energy may have made them, on average, more severe. Key words: Agrometeorology, land-use change, thunderstorms

Copper in cultivated soils of Finland

Soil samples from the plough layers of 105 fields in different parts of Finland were analyzed for Cu fractions. Vertical distribution of Cu was also studied in a smaller material. Total Cu (Cutot , HNO3-HCIO4-HF-H2SO4 digestion) in the surface soil ranged 6.9-97.4 mg kg-1 (mean 37.1 mg kg-1) and was highest in clay soils (mean 59.0 mg kg-1) and lowest in fine sand and moraine soils (mean 18.3 mg kg-1 ). Copper in the water-soluble, exchangeable and mainly organically bound fraction was extracted with 0.1 M K4P2O7 (Cupy), and Cu bound by poorly crystalline Fe, A and Mn oxides (Cuox) was dissolved subsequently with 0.05 M oxalate (pH 2.9). The average percentages of Cupy and Cuox were 18% and 12% of Cutot in mineral soils and 34% and 19% of Cutot in organogenic soils, respectively. Residual Cu (Cures ) incorporated in mineral lattices was calculated to constitute 70% and 47% of Cutot in mineral and organogenic soils, respectively. In two thirds of soils the potentially plant-available reserves of Cu (Cupy + Cuox) were more plentiful than those of Zn (Znpy + Znox). An acetic acid - ammonium acetate - Na2EDTA solution used in routine soil testing extracted 56% and 71% of the sum of Cupy + Cuox in mineral and organogenic soils, respectively. In soil profiles, CuEDTA was higher in the plough layer than in the subsoil but a few soils rich in Cutot had abundant reserves of CuEDTA below the rooting depth of annual field crops.

Conservation ofBacillus thuringiensisefficacy in New Zealand through the planned deployment ofBtgenes in transgenic crops

Although the use of Bacillus thuringiensis (Bt) as a foliar spray is minimal within New Zealand at present, a considerable effort is being made genetically to incorporate Bt δ‐endotoxin genes into a wide range of important crops, including pasture species, perennial horticultural crops and annual field crops. For several years it has been clear that the major threat to the sustained efficacy of Bt in New Zealand is the evolution of insect resistance. Recognition of this threat has prompted consideration of a range of strategies for preventing and/or managing its possible evolution in pests of specific crops. However, such strategies do not address the critical issue of how we might limit the consequences of Bt resistance if it did evolve, particularly the evolution of resistance in polyphagous pests. Highly mobile polyphagous pests, such as leafroller species, might develop resistance to Bt on one transgenic crop and then disperse, nullifying the effectiveness of a wide range of Bt transgenic crops expressing the same or similar Cry proteins. Pests with resistance to CryIA proteins in transgenic plants might also display significant resistance to Bt biopesticides. To prevent such an eventuality in New Zealand we propose a plan for deploying Bt genes among crops according to an assessment of the risk and consequences of Bt resistance evolving in the insect complexes on these crops. The major elements of this plan are: (i) assess the risk of Bt resistant insects evolving and dispersing out of the crop to infest others; (ii) characterize the diversity of Bt protein binding sites in the guts of key polyphagous pests; (iii) use the above information to deploy Bt genes among different transgenic crops in a pattern that minimizes the chance that any future Bt resistant cosmopolitan pests will be broadly cross‐resistant to other Bt crops and/or Bt biopesticides.

A Water Use Index For Crop Performance

A weather-based crop growth index (GRODEX) was developed using daily soil water budgeting principles and assumed generalized plant water use characteristics. The model combines soil moisture reserves, temperature stress, growing season limits and harvest losses. Examples are given of the index performance using 74 weather stations across Canada. The index is related to vegetation eco-regions of Canada to show general differences and similarities in biomass production for annual field crops.

Differentiation of Selected Annual Field Crops Throughout the Growing Season by their Spectral Reflectance Properties

(1977). Differentiation of Selected Annual Field Crops Throughout the Growing Season by their Spectral Reflectance Properties. Canadian Journal of Remote Sensing: Vol. 3, No. 1, pp. 55-65.

Effects of Energy Cost Increases and Regional Allocation Policies on Agricultural Production

AbstractSome of the impacts of energy cost increases and reduced supplies on the product mix of annual field crops and vegetables in California are analyzed. A quadratic programming model including risk is used to evaluate the effects of increased energy costs and reductions in fertilizer and in fuel supplies. The model includes a demand matrix of some nine field crops and twenty‐eight seasonal vegetables. The study also considers the relative impact of energy changes on producer and consumer welfare. Results suggest continued viability of vegetable production but differential consumer and producer impacts associated with energy changes.

Effect of zero-tillage on organic carbon and total nitrogen content, and their distribution in different N-fractions in loessial soils

In order to evaluate the effect of reduced tillage intensity on the accumulation of organic matter in Grey-brown podsolic soils near Göttingen (German Federal Republic), stratified soil analyses were made in three field trials after at least 5 years of experimenting. On old arable soil, zero-tillage increased the content of organic C of the 0–30 cm layer by mean annual rates of 0.59–1.30 tons/ha, and correspondingly the content of total N by 53.8–72.4 kg/ha. Killing a sod and cropping the former grassland with annual field crops, but without disturbing the soil, caused a mean annual loss of 2.29 tons/ha and 162.4 kg N/ha. This indicates that reduced tillage cannot preserve the original high content of soil organic matter maintained by a living sod. On arable soil, zero-tillage caused a mode of nitrogen distribution which is similar to that found in grassland soil. The N-content of fraction V (containing total amino-acid N and unknowns) increased at the expense of the ammonium-N (fraction I). The relative increase or loss of total N in the 0–5 cm layer, as caused by tillage and cropping practices, was most pronounced in fraction V, ranging between 53 and 67%.

Availability Characteristics Of and Plant Response to Nitrogen Sources

AbstractThe relative availability characteristics of nitrogen in urea, cottonseed meal, a commercial urea‐formaldehyde product, and an experimental urea‐wax material were studied through successive leachings in model lysimeters in the laboratory and by leaching and plant growth in the greenhouse. The effects of the nitrogen sources on yield and chemical composition of field‐grown tobacco were studied under different moisture regimes.The total release of nitrogen from the urea‐wax source was comparable to that from urea but significantly higher than from urea‐formaldehyde or cottonseed meal sources. The rate of N release during the first 21 days was not different among the urea‐wax, urea‐formaldehyde, and cottonseed meal sources; thereafter, it was higher from urea‐wax. When differences in crop response occurred among the different sources, the yield and quality index were higher from urea‐wax than from cottonseed meal or urea‐formaldehyde. These results and data from other research suggest that the probability of practical contributions of slow release fertilizers in the commercial production of annual field crops is quite small.

Mixed Cropping-A Review

Mixed cropping is a system of Agriculture in which two or more crops are grown together at the same time in the same land. It is a common practice in tropical countries both with annual field crops and with perennial plants like fruit trees, flower plants and plantation crops. This type of cropping prevails in Africa, India, Ceylon, Malaya, China and West Indies. It is also usual to grow annual herbaceous crops in the midst of woody perennial trees of economic importance such as coconut, mango, jack and other fruit trees. "The group of plants growing together form a plant society like the natural plant societies that occur on any piece of land leit to nature." (Willis, 1909).

Problems in Estimating Texas Citrus Fruit

Grapefruit is the principal citrus crop in Texas, and problems in production are practically the same for grapefruit and oranges. This paper, therefore, will relate to grapefruit specifically rathern than to citrus as a whole. Also, as the more perplexing problems are encountered in production, rather than in estimating final production, forecasting might be substituted appropriately in the title for estimating. The final estimates are based largely upon tangible and accessible data, such as complete records of shipments and quantities processed. Methods used in preparing production forecasts of field crops involve the solution of the two major problems of determining the acreage of the crop and deriving significant pre-harvest indications of probable yield per acre. Of the two phases, the problem of estimating acreage each year is the more difficult one. The problem of estimating production of tree fruits, however, is somewhat different Changes in bearing acreage usually occur more gradually, and, because the trees are long-lived, the changes are more predictable on the basis of enumerations and sample surveys made at two to five year intervals. The obtaining of dependable indications from yield per acre or yield per tree inquiries for use in is much more difficult for tree fruits than it is for annual field crops, for a number of reasons. Differences in ages of trees, number per acre, and potential capacity among different orchards in a locality make it difficult for crop reporters to estimate on the basis of yield per tree without spending more time than they, as voluntary reporters, are willing to give. Even if such reports could be obtained, the extreme variation between locality reports would involve serious difficulties in sampling and in interpretation. Because of these differences in the basic problems, the Department has found it necessary to develop different approaches in and estimating most fruit crops. Before discussing grapefruit problems in particular, the methods used in other fruits will be mentioned briefly. The most useful inquiry, from the standpoint of ease in estimating by the farmer, and in reflecting variations in seasonal factors, has been the simple request to report on condition in per cent of a full crop. In addition to the advantage of being relatively easy for the farmer to estimate, this inquiry removes the extreme variation