Average Yield Ratio Research Articles

Meta‐Analysis of the Effect of Nitrogen Fertilization on Annual Cereal–Legume Intercrop Production

Numerous studies have been performed to study the effect of N fertilization on cereal–legume intercrops, and their results are sometimes conflicting. Our objective was to do a meta‐analysis on cereal–legume intercrops testing the effects of N fertilization on land equivalent ration (LER; partial and total LER), yield ratio, and proportion of legume in the mixture of crop grains. This analysis was based on 17 published studies reporting the results of experiments performed in 15 countries on six species of cereals and 10 species of legumes. Experiments were generally based on replacement (50–50, i.e., in the intercrop, each species is sown at half the sowing rate used for the sole crop) or full substitutive (100–100, i.e., the sowing rate for each crop in the intercrop is identical to that for sole crops) designs. Nitrogen fertilization rates ranged from 0 to 180 kg N ha−1. The effect of N fertilization and its inter‐study variability were analyzed with mixed‐effect statistical models, including study as a random effect. Results showed that N fertilization had non‐significant effects on average LER and average yield ratio but that the inter‐study variability of these effects was large. Nitrogen fertilization was found to significantly decrease the grain proportion of the legume in the mixture and the partial LER of the legume in studies based on C3 cereal intercrops. The database used for the meta‐analysis is freely available (http://www6.versailles‐grignon.inra.fr/agronomie/Meta‐analysis‐in‐agronomy/Datasets/Dataset‐Intercrop).

Determination of 235U isotopic abundance by fission-yield difference method

Based on neutron activation analysis, a new method was presented for the determination of uranium isotopic abundance, in which fast neutrons generated by T (d, n) 4He were used to induce fission in uranium samples. The exponential relation between different abundances of 235U and the average fission-yield ratios of specific fission products was employed in this method. Taking the fission-yield ratios of specific fission products, such as Y¯88Rb/Y¯107Rh, Y¯88Rb/Y¯135I, Y¯88Rb/Y¯104Tc and Y¯92Sr/Y¯104Tc as the subjects of research, the relation curves between the average yield ratios and the 235U isotopic abundance as well as the expressions (Y¯i/Y¯j=f(H0)) for the average yield ratio (Y¯i/Y¯j) as a function of the 235U isotopic abundance (H0) were obtained. To verify the precision and accuracy of this method, 5 tests using each working curve were conducted for simulated samples with a 235U abundance of 72.2%, and the relative standard deviation (RSD) of all tests was less than 2%. Compared to the γ energy spectrum method, the relative error of each measurement result was between 1.11% and 1.66%.

Successful Isolation and PCR Amplification of DNA from National Institute of Standards and Technology Herbal Dietary Supplement Standard Reference Material Powders and Extracts

Twenty-four herbal dietary supplement powder and extract reference standards provided by the National Institute of Standards and Technology (NIST) were investigated using three different commercially available DNA extraction kits to evaluate DNA availability for downstream nucleotide-based applications. The material included samples of Camellia, Citrus, Ephedra, Ginkgo, Hypericum, Serenoa, And Vaccinium. Protocols from Qiagen, MoBio, and Phytopure were used to isolate and purify DNA from the NIST standards. The resulting DNA concentration was quantified using SYBR Green fluorometry. Each of the 24 samples yielded DNA, though the concentration of DNA from each approach was notably different. The Phytopure method consistently yielded more DNA. The average yield ratio was 22 : 3 : 1 (ng/microL; Phytopure : Qiagen : MoBio). Amplification of the internal transcribed spacer II region using PCR was ultimately successful in 22 of the 24 samples. Direct sequencing chromatograms of the amplified material suggested that most of the samples were comprised of mixtures. However, the sequencing chromatograms of 12 of the 24 samples were sufficient to confirm the identity of the target material. The successful extraction, amplification, and sequencing of DNA from these herbal dietary supplement extracts and powders supports a continued effort to explore nucleotide sequence-based tools for the authentication and identification of plants in dietary supplements.

Organic agriculture and the global food supply

AbstractThe principal objections to the proposition that organic agriculture can contribute significantly to the global food supply are low yields and insufficient quantities of organically acceptable fertilizers. We evaluated the universality of both claims. For the first claim, we compared yields of organic versus conventional or low-intensive food production for a global dataset of 293 examples and estimated the average yield ratio (organic:non-organic) of different food categories for the developed and the developing world. For most food categories, the average yield ratio was slightly <1.0 for studies in the developed world and >1.0 for studies in the developing world. With the average yield ratios, we modeled the global food supply that could be grown organically on the current agricultural land base. Model estimates indicate that organic methods could produce enough food on a globalper capitabasis to sustain the current human population, and potentially an even larger population, without increasing the agricultural land base. We also evaluated the amount of nitrogen potentially available from fixation by leguminous cover crops used as fertilizer. Data from temperate and tropical agroecosystems suggest that leguminous cover crops could fix enough nitrogen to replace the amount of synthetic fertilizer currently in use. These results indicate that organic agriculture has the potential to contribute quite substantially to the global food supply, while reducing the detrimental environmental impacts of conventional agriculture. Evaluation and review of this paper have raised important issues about crop rotations under organic versus conventional agriculture and the reliability of grey-literature sources. An ongoing dialogue on these subjects can be found in the Forum editorial of this issue.

An Ecological Study of Arthropod Populations on Apple in Northeastern Wisconsin: Species Affecting the Fruit1

The effect of insect populations on fruit was studied in a mature apple orchard under a natural and 2 artificial environments from 1959 through 1962. About 15, approximately 2%, of the 763 species collected from the orchard injured the fruit directly. Ninety-nine to 100% of the apples in the check and captan environments were injured each year, with the plum curculio, Conotrachelus nenuphar (Herbst); apple maggot, Rhagoletis pomonella Walsh; and codling moth, Carpocapsa pomonella (L.), causing most of the injury, in that order. Fruit injury by other species in the check and captan environments was insignificant. Injury in the DDT-captan block was gencrally low except for that caused by larvae of red-banded leaf roller, Argyrotaenia velutinana (Walker), and of eye-spotted bud moth, Spilonota ocellana (Denis and Schiffermüller), which progressively increased each year. Apple scab, Venturia inequalis (Winters), was an important factor in the natural (check) environment, affecting tree growth, fruiting, and insect populations. The last mentioned were generally favorably affected in the captan environment, and adversely so in the DDT-captan. Fruit production increased substantially from the check to the captan and DDT-captan blocks with an average yield ratio of 1:1.2:2.1, respectively, for the 4-year study. An additive effect was obtained with the use of DDT in the DDT-captan block, which was greater than the combined effect of scab and insect population suppression, resulting in increased tree vigor and fruit set which improved each year.