The Journal of Agricultural Science
About: The Journal of Agricultural Science is an academic journal. The journal publishes majorly in the area(s): Fertilizer & Sowing. It has an ISSN identifier of 0021-8596. Over the lifetime, 12947 publication(s) have been published receiving 244921 citation(s). The journal is also known as: The Journal of agricultural science.
Papers published on a yearly basis
Abstract: A method is proposed for estimating the percentage of dietary protein that is degraded by microbial action in the rumen when protein supplement is added to a specified ration. The potential degradability, p , is measured by incubating the supplement in artificial-fibre bags in the rumen and is related to incubation time, t , by the equation p = a+b (1 – e -ct ). The rate constant k , measuring the passage of the supplement from the rumen to the abomasum, is obtained in a separate experiment in which the supplement is combined with a chromium marker which renders it completely indigestible. The effective percentage degradation, p , of the supplement, allowing for rate of passage, is shown to be p = a +[ bc/(c+k) ] (1- e -(e+k)t ) by time, t , after feeding. As t increases, this tends to the asymptotic value a+bc /( c+k ), which therefore provides an estimate of the degradability of the protein supplement under the specified feeding conditions. The method is illustrated by results obtained with soya-bean meal fed as a supplement to a dried-grass diet for sheep. The incubation measurements showed that 89% of the soya-bean protein disappeared within 24 h and indicated that it was all ultimately degradable with this diet. When the dried grass was given at a restricted level of feeding the allowance for time of retention in the rumen reduced the estimate of final degradability to 71% (69% within 24 h). With ad libitum feeding there was a faster rate of passage and the final degradability was estimated to be 66% (65% within 24 h).
E.-C. Oerke1•Institutions (1)
TL;DR: Despite a clear increase in pesticide use, crop losses have not significantly decreased during the last 40 years, however, pesticide use has enabled farmers to modify production systems and to increase crop productivity without sustaining the higher losses likely to occur from an increased susceptibility to the damaging effect of pests.
Abstract: Productivity of crops grown for human consumption is at risk due to the incidence of pests, especially weeds, pathogens and animal pests. Crop losses due to these harmful organisms can be substantial and may be prevented, or reduced, by crop protection measures. An overview is given on different types of crop losses as well as on various methods of pest control developed during the last century.Estimates on potential and actual losses despite the current crop protection practices are given for wheat, rice, maize, potatoes, soybeans, and cotton for the period 2001–03 on a regional basis (19 regions) as well as for the global total. Among crops, the total global potential loss due to pests varied from about 50% in wheat to more than 80% in cotton production. The responses are estimated as losses of 26–29% for soybean, wheat and cotton, and 31, 37 and 40% for maize, rice and potatoes, respectively. Overall, weeds produced the highest potential loss (34%), with animal pests and pathogens being less important (losses of 18 and 16%). The efficacy of crop protection was higher in cash crops than in food crops. Weed control can be managed mechanically or chemically, therefore worldwide efficacy was considerably higher than for the control of animal pests or diseases, which rely heavily on synthetic chemicals. Regional differences in efficacy are outlined. Despite a clear increase in pesticide use, crop losses have not significantly decreased during the last 40 years. However, pesticide use has enabled farmers to modify production systems and to increase crop productivity without sustaining the higher losses likely to occur from an increased susceptibility to the damaging effect of pests.The concept of integrated pest/crop management includes a threshold concept for the application of pest control measures and reduction in the amount/frequency of pesticides applied to an economically and ecologically acceptable level. Often minor crop losses are economically acceptable; however, an increase in crop productivity without adequate crop protection does not make sense, because an increase in attainable yields is often associated with an increased vulnerability to damage inflicted by pests.
Abstract: § 34. 1. The permeability and capillarity constants of soil have been defined.2. The movements of air and water through three types of soil have been measured and shewn to conform to equations connecting the rate of motion with the above constants.3. It is suggested that the measurement of S, Pα, Pω and K is of more importance than, and should replace, the determination of the sizes of the soil particles as in the usual “mechanical analysis” of soils.In conclusion, we have to acknowledge our indebtedness to Professors T. R. Lyle and R. J. A. Barnard for valuable advice and suggestions and to the Victorian Government for financial assistance towards the expenses of this research.
Abstract: A rapid and accurate atomic absorption method for the determination of chromium in faeces samples from pasture experiments using chromic oxide ‘markers’ is described. Of the elements present after ashing and digesting the samples in a phosphoric acid—manganese sulphate—potassium bromate solution silicate, aluminium, calcium and magnesium were found to interfere in the determination. The effects of these interferences were overcome by the addition of calcium to the test solution and by the addition of silicate to the standards, which were prepared in ‘blank’ solutions.The sensitivities of a number of alternate chromium resonance lines relative to that of Cr 3578·7 A. are given. These lines may be used to increase the concentration range of the analysis.The results of a comparison of the atomic absorption method with a chemical method are given.
TL;DR: A rapid method for measuring gas production during incubation of feedingstuffs with rumen liquor in vitro was described and gas production in 24 h from 200 mg feed dry matter was well correlated with digestibility of organic matter, determined in vivo with sheep.
Abstract: A rapid method for measuring gas production during incubation of feedingstuffs with rumen liquor in vitro is described. Gas production in 24 h from 200 mg feed dry matter was well correlated with digestibility of organic matter, determined in vivo with sheep. Multiple regression analysis, when it included data from proximate analysis, resulted in an equation ( R = 0·98) for prediction of metabolizable energy content, based on 30 experiments with rations varying in protein and crude fibre content, and 59 other experiments with concentrates. Energy content was in the range of 7·7–13·2 MJ ME/kg D.M. ( ± S.D. = 11·17 ± 1·08). The residual standard deviation of the equation was 0·25 MJ. Gas production was measured in calibrated syringes. The only chemical determinations needed are dry matter, protein and fat. Differences in activity between batches of rumen liquor are corrected by reference to gas production with standard feedingstuffs (hay meal and maize starch).
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