A rapid method of testing plants in the field for potato virus X

American Journal of Potato Research - A method is described whereby a team of four people can use a variant of the serological precipitin reaction to test over 125 plants an hour in the field for...     

A comparison of conventional and automatic milking system pasture utilization and pre‐ and post‐grazing pasture mass

Automatic milking systems (AMS) present an opportunity for dairy farmers to not only improve their lifestyle and conditions of work, but also save on labour costs and/or increase the time available to focus on overall farm management. However, the viability of AMS will rely on achieving high levels of pasture utilization. Well‐established pasture management principles are implemented on many conventional milking system (CMS) farms and high levels of pasture utilization are achieved; however, the ability to follow these same principles on AMS is unknown. This study compared levels of pasture utilization and pre‐ and post‐grazing pasture mass between AMS and CMS farms at the same site when managed by the same pasture management principles. From 1 March 2007 to 29 February 2008, pre‐ and post‐grazing compressed height, milk yield and milk composition data were collected for two CMS farms and one AMS farm at the Elizabeth Macarthur Agricultural Institute, Camden, Australia. Despite differences in pre‐ and post‐ grazing pasture mass between milking systems, pre‐grazing mass was predominantly maintained within the bounds of 2200 and 2500 kg DM ha^?1 and post‐grazing mass between 1400 and 1500 kg DM ha^?1 (5–6 cm height). Similar levels of pasture utilization (mean 13 500 kg DM ha^?1 year^?1) were recorded between AMS and CMS farms. These findings highlight the ability to follow established grazing management principles and achieve high levels of pasture utilization on pasture‐based AMS farms.     

A practical equation for pasture growth under grazing

A sigmoid equation that accurately describes pasture growth is presented. The equation has three parameters that can be estimated either statistically from experimental results or algebraically from physiological simulation models. The equation produces satisfactory statistical results and it can account for different environmental conditions, through adjustment of parameter values, making it ideal for incorporation into grazing models when a simple but flexible equation is needed.     

A simulation model to predict the drying time for pasture hay

A hay drying model (HAYDMO) which predicts the moisture content of pasture hay is described. It uses multiple regression equations based on field drying experiments with conditioned and unconditioned hay and predicts hourly changes in moisture content for both day and night and also those due to rain. The model can be used with three different combinations of weather, including hourly wet and dry bulb temperatures, radiation, wind speed and rainfall. Testing HAYDMO revealed a satisfactory agreement between predicted and observed moisture contents     

A technique for estimating rate of disappearance of dead herbage in pasture

A technique for estimating the rate of disappearance of material from samples of dead herbage protected by simple nylon or wire mesh covers is described. Using this technique on a perennial ryegrass sward in southern England during August-November, relative rates of disappearance close to 0·204 g g^-1 d^-1 (DM) were obtained, but the variability was high. When herbage killed with paraquat was used, the rate of disappearance was higher and the variability lower. There were only small differences in the temperatures recorded in a normal sward and within samples of dead herbage under mesh covers.     

A forage dynamics model for use in range or pasture environments

A deterministic model that simulates forage dynamics is described and validation results presented. The model simulates different species of grasses and forbs for a production year and provides the necessary input for a diet selection model. The model does not simulate growth, but does simulate the accumulation of live leaf and stem, the senescence of live biomass, and its transfer to dead mass using growth rates for leaf and stem of each species, which are specified for the model. Using such an approach specific types of years can be simulated. Plant components in the model include live leaf and stem, dead leaf and stem, and old dead leaf and stem which were produced during the previous growing season. These plant components were chosen because of their importance in the diet selection process and their differences in forage quality. Plant species which the model was validated against were Cynodon dactylon, Avena sativa. Schizachyrium scoparium and Paspalum plicatulum. Validation results indicated that with adjustment to input growth rates, live biomass could be adequately simulated. Deviations between measured and simulated dead components were observed for S. scoparium and P. plicatulum. High values observed for dead stem early in the trial resulted from lack of separation of dead and old dead stem material in the field sampling. Variations in dead forage throughout the season were caused by unexplained sources of variation. This indicated a need for field research to better quantify the dynamics of dead biomass. The model meets its goal of simulating biomass dynamics and forage quality of plant parts and it provides a suitable forage base to interface with diet selection and animal simulation models.     

A system for the rapid collection,analysis and dissemination of aphid-monitoring data from suction traps

The Rothamsted Insect Survey monitoring scheme, currently operating 12·2 m suction traps at 23 sites, provides regular information on the abundance and distribution of aphid pest species to assist growers and advisors in pest-control decision-making. The method of collecting and identifying the insect samples and handling the resulting data to minimize errors is described. Data summaries and interpretations are disseminated widely throughout the agricultural industry. The long run of data provides valuable opportunities for future research and for improving the interpretation of the data for advisory purposes.     

A statistical assessment of the dry-weight-rank method of pasture sampling

The statistical properties and applicability of the Dry-Weight-Rank (DWR) method of pasture sampling are examined. Formulae for the expected value and variance of the DWR estimates are presented.
The extent of bias in DWR is examined using several mathematical models. DWR is shown to break down when estimating multinomial proportions; however it provides good estimates for a subset of models simulated from a class of compound probability distributions.
The success of DWR in practice does not rest on a theoretical basis. It appears to be a remarkable empirical discovery that DWR estimates are virtually unbiased on most pasture types. Several cases are considered where difficulties may be encountered in using DWR. Provided the theoretical reservations of this paper are borne in mind, DWR will continue to be a useful practical tool, especially in the absence of non-destructive observational alternatives.     

A method for the rapid estimation of glycoalkaloids in potato tubers

A rapid method for estimating glycoalkaloid levels in potato tubers has been developed. It is basically a screening technique whereby large numbers of samples can be assigned to categories of alkaloid level such as very low, low, medium and high. The elapsed time is typically four hours and the per sample time 12 to 15 minutes when large numbers are run. Weighed tuber samples are cut up and blended with a volume (ml) of extracting solution equal to the weight of the sample in g. After blending for four minutes, a portion of the extract is poured on to a fluted filter. An aliquot of the filtrate is treated with an antimony trichloride reagent and the color is read at 550 nm after 15 min.     

Cultivation system influenced the critical period for weed control in cotton field

Background The critical period of weed control(CPWC) refers to the period of time during the crop growth cycle when weeds must be controlled to prevent yield losses. Ultra-narrow row(UNR) is a method of planting of cotton in rows that are 25 cm or less apart. Amongst cultural techniques for weed control, the use of narrow row spacing is considered to be a most promising approach that can effectively suppress weed growth and provide greater yields in cotton. This cultivation system can shorten th...     

Potential pasture production in the uplands of Wales

Only a very limited number of species, including red fescue (Festuca rubra) , perennial ryegrass ( Lolium perenne) , timothy (Phleum protense) and white clover (Trifolium repens) are considered as suitable for wet hill land. Detailed comparison of red fescue, perennial ryegrass and timothy on contrasting acid brown earth and stagnogley soils from 1966 to 1969 at Pant-y-dŵr Hill Centre (305 m OD) highlighted the advantages of red fescue in annual DM production and its more even distribution over a longer growing season but also indicated drawbacks of slow initial establishment and lower feed quality. In vitro DOMD of red fescue averaged 645 g kg⁻¹ over the year compared with 690 g kg⁻¹ for perennial ryegrass and timothy. Assessment of a narrow range of species under surface seeding conditions on a stagnogley soil from 1971 to 1975 confirmed the value of red fescue in DM production and persistence. The results are discussed in relation to the characteristics required in herbage species for hill land improvement.     

A rapid method for the estimation of damaged starch in wheat flours

A new method was developed for determination of damaged starch in wheat flour. The method was based on the idea that the difference between the soluble matter contents of the extracts prepared from the same flour with and without alpha-amylase is mainly due to the action of alpha-amylase on damaged granules. The extraction stage of the method is similar to the AACC method (76-30A). However, after this stage a refractometer was used to measure Brix values of solutions instead of determination of reducing sugars. The sample size and incubation period of the AACC method were optimized for the proposed method using response surface methodology. The damaged starch levels of twenty-five commercial samples were determined by the proposed method as well as the two AACC Methods (No: 76-30A and 76-31). The results of the proposed method are compared with the results of the AACC Methods by using regression analysis. The correlation coefficients between the proposed method and both of the AACC Methods were 0.99. The average absolute differences between the proposed method and the AACC methods were 3.9 and 5.0%, respectively. The proposed method can be completed in 30 min with low number of experimental steps. The results showed that the starch damage values measured by the new method could be viewed with as much confidence as the traditional AACC Method 76-30A.     

A tissue culture method for the rapid propagation of potatoes

A tissue culture method for the rapid propagation of potatoes was studied using 38 varieties. At least 50 plantlets were regeneratedin vitro, in a sequential procedure, from a single isolated shoot tip. Rapid proliferation of shoots was enhanced by shake culture of previously differentiated organogenic cultures. These shoots in turn were used to regenerate complete plantlets by the culture of nodal sectionsin vitro. Culture initiation was more dependent on the variety than culture proliferation. The culture media contained the Murashige-Skoog basal components supplemented with 6-benzylaminopurine, gibberellic acid and naphthalene acetic acid. The system described, whereby high propagation rates can be achieved, was referred to as “multi-meristem” culture in contrast to the 1:1 rate normally obtained by the conventional, “single-meristem” culture. Evaluations of varietal stability, using both biochemical and morphological criteria showed no detectable changes due to thein vitro procedures. It is proposed to utilize the “multi-meristem” propagation technique for the conservation and international distribution of valuable clonal germplasm.     

Coefficients for the dry-weight rank method of botanical analysis of pasture

The coefficients of the dry-weight-rank (DWR) method ('t Mannetje & Haydock, 1963) can be predicted from the general occurrence of the geometric series relationship between abundance and rank of species in a pasture using either an estimate of the percentage contribution of the first ranked species, or from the ratio of the contribution of two species.     

Variations in composition of pasture herbage

Changes in the chemical composition of pasture samples from five dairy farms were observed over a 2-year period. Many of the minerals were at their lowest concentration in samples taken in the spring and early summer. At these times the concentrations of P, Mg and Na were often less than sufficient to meet the calculated requirements of the dairy cow fed on pasture alone. Cu and Co concentrations in the herbage were also generally low relative to the needs of the dairy cow.     

一种快速有效油用亚麻转基因体系的建立

油用亚麻(俗称胡麻)是我国重要的油料作物之一,也是干旱和半干旱地区的主要经济作物.近年来随着国家经济的发展和人们生活质量的提高,人们对油用亚麻的需求逐渐提升.建立一种快速高效便捷的油用亚麻遗传转化体系对油用亚麻分子育种具有重要意义.本实验以油用亚麻子叶节作为遗传转化的外植体,以草铵膦作为转基因植株筛选剂,通过农杆菌介导...     

A comparison between barley and groundnut as supplements for dairy cows at pasture

In two 12-week grazing experiments using twelve and eighteen spring-calved cows in 1976 and 1977 respectively, the effects of feeding either a barley or a groundnut concentrate supplement were investigated. The mean yield of herbage DM on offer was 2330 and 2030 kg ha^-1, with crude protein concentrations of 192 and 193 g per kg DM in 1976 and 1977 respectively. Grazed herbage was the sole feed in the control treatment. In the other two treatments the herbage was supplemented with 3 kg per cow per d of a concentrate containing either 82·2% barley or groundnut with mean crude protein concentrations of 109 and 409 g per kg DM respectively. Similar results were obtained in both experiments with average daily milk yields of 18·3, 19·8 and 19·9 kg per cow on the control, barley and groundnut treatments respectively. The supplements had no significant effects on either milk composition or liveweight change. It is concluded, that with an ample supply of herbage of high crude protein concentration, a supplement of groundnut had no advantages over one of barley.     

A rapid method for the determination of sulphur dioxide in sulfited potato flakes

A simple and rapid method is presented for the determination of sulfite in dehydrated potato flakes. Special extraction and filtration techniques are used to prevent potato cell rupture and subsequent release of the starch. Presence of cooked starch would interfere greatly with filtration of the extract. An iodimetric titration and simple calculation yield reproducible results with little effort or time.