Effects of epigeic earthworm (Eisenia fetida) and arbuscular mycorrhizal fungus (Glomus intraradices) on enzyme activities of a sterilized soil–sand mixture and nutrient uptake by maize

A pot experiment was conducted to investigate the effect of epigeic earthworm (Eisenia fetida) and arbuscular mycorrhizal (AM) fungi (Glomus intraradices) on soil enzyme activities and nutrient uptake by maize, which was grown on a mixture of sterilized soil and sand. Maize plants were grown in pots inoculated or not inoculated with AMF, treated or not treated with earthworms. Wheat straw was added as a feed source for earthworms. Mycorrhizal colonization of maize was markedly increased in AM fungi inoculated pots and further increased by addition of epigeic earthworms. AM fungi and epigeic earthworms increased maize shoot and root biomass, respectively. Soil acid phosphatase activity was increased by both earthworms and mycorrhiza, while urease and cellulase activities were only affected by earthworms. Inoculation with AM fungi significantly (p?<?0.001) increased the activity of soil acid phosphatase but decreased soil available phosphorus (P) and potassium (K) concentrations at harvest. Addition of earthworms alone significantly (p?<?0.05) increased soil ammonium-N content, but decreased soil available P and K contents. AM fungi increased maize shoot weight and root P content, while earthworms improved N, P, and K contents in shoots. AM fungi and earthworm interactively increased maize shoot and root biomass through their regulation of soil enzyme activities and on the content of available soil N, P, and K.     

Electronic Journal of Extension: From Hard Copy to Electronic Format–An Evaluation of a Pilot Test

ABSTRACT

In 1992 the Journal of Extension's Board of Directors authorized a pilot project to test the feasibility of producing and distributing the Journal electronically as a means of reducing the direct and indirect costs of publication. The University of Wisconsin-Extension headed the pilot test and the University of Missouri-Extension was asked to conduct a comprehensive evaluation of the electronic Journal of Extension. This article describes the purposes, methods, content, and preliminary findings of the evaluation of this pilot project.     

How many soil samples are neccessary to obtain a reliable estimate of mean nitrate concentrations in an agricultural field?

In Germany, field‐average soil NO₃^‐ measurements are used to identify agricultural risks of groundwater pollution and to evaluate the compliance of land users with environmental regulations. In the present study, it was tested at three typical agricultural sites if common practices of soil NO₃^‐ sampling were appropriate to obtain reliable estimates of the mean field NO₃^‐ content in fall. Three sites of 1 ha area were extensively sampled for NO₃^‐. Ordinary statisticial analyses were conducted on the NO₃^‐ data in order to calculate how many samples per ha were required to predict the mean field NO₃^‐ with a given accuracy. Variograms were derived to assess applicability and relevance of ordinary statistical methods for heterogeneous fields. Results from statistical analysis suggest that at two sites common practices of soil NO₃^‐ sampling would have been adequate to obtain estimates of the actual mean field NO₃^‐ content with a sampling error less than 10 kg NO₃^‐‐N ha^—1 at a 95% probability level. At the other site, common practices obviously would have failed because NO₃^‐ contents varied much more spatially. It remains a problem of soil sampling for NO₃^‐ analysis that information on field heterogeneity is frequently not available a priori.     

What do babies eat? Evaluation of a food frequency questionnaire to assess the diets of infants aged 6 months

OBJECTIVE: To evaluate the relative validity of a food frequency questionnaire (FFQ) for assessing nutrient intakes in 6-month-old infants. DESIGN AND SETTING: The FFQ was developed to assess the diets of infants born to women in the Southampton Women's Survey (SWS), a population-based survey of young women and their offspring. The energy and nutrient intakes obtained from an interviewer-administered FFQ were compared with those obtained from a 4-day weighed diary. SUBJECTS AND METHODS: A sub-sample of 50 infants aged 6 months from the SWS had their diets assessed by both methods. The FFQ recorded the frequencies and amounts of milks, baby foods, regular foods and drinks consumed by the infants over the previous seven days. The diaries recorded the weights of all foods and drinks consumed by the infants on four separate days within 15 days following FFQ completion. RESULTS: Spearman rank correlation coefficients for intakes of energy, macronutrients and 18 micronutrients, determined by the two methods, ranged from r = 0.39 to 0.86; adjustment for energy intake tended to increase the correlation coefficients, range r(a) = 0.55 to 0.89. Bland-Altman statistics showed that mean differences between methods were in the range of -12.5% to +12.5% except for vitamin B12 (-18.9%). CONCLUSION: Although there were differences in absolute energy and nutrient intakes between methods, Spearman rank correlation coefficients indicated reasonable agreement in the ranking of intakes. The interviewer-administered FFQ is a useful tool for assessing energy and nutrient intakes of healthy infants aged about 6 months.     

Can phosphorus (P)-releasing bacteria and earthworm (Eisenia fetida L.) co-enhance soil P mobilization and mycorrhizal P uptake by maize (Zea mays L.)?

Journal of Soils and Sediments - Both earthworm (Eisenia fetida L.) and phosphorus (P)-releasing (PR) bacteria, including organic P-mineralizing (OPM) and inorganic P-solubilizing (IPS), are able...     

Stretching Soil Sampling to Watershed: Evaluation of Soil‐Test Parameters in a Semi‐arid Tropical Watershed

Soil sampling is an integral component of fertility evaluation and nutrient recommendation for efficient use of nutrients in crop production. Little attention has been devoted to evaluating methodology for sampling watersheds under dryland agriculture. A stratified random sampling methodology for sampling the Appayapally watershed in Mahabubnagar district of Andhra Pradesh state in the semi‐arid tropical region of India was adopted and evaluated. The watershed has an area of about 500 ha, with gentle sloping lands (<1% slope), and 217 farmers own land in the watershed. The soils are Alfisols. A total of 114 soil samples were collected from the top 15‐cm layer to represent the entire watershed. Each sample was a composite of 7–8 cores, randomly collected from the area represented by a crop and group of farmers. The soil samples were air dried, ground, and analyzed for pH, electrical conductivity (EC), organic carbon (C), total nitrogen (N), and extractable phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), sodium (Na), sulfur (S), zinc (Zn), manganese (Mn), iron (Fe), copper (Cu), and boron (B). Statistical analysis of the results on soil fertility parameters showed that the mean‐ or median‐based results of soil tests performed in the study did not differ significantly when the sample set size varied from 5 to 114 (100% of the population). Our results indicate that farmers' fields in the Appayapally watershed are uniform in the chemical fertility parameters studied, and even a small sample set size can represent the whole population. However, such a sampling strategy may be applicable only to watersheds that are very gently sloping and where fertilizer use is very low, resulting in an overall low fertility in the whole watershed.     

Evaluation of Assouline–Or Adjusted Model to Express Soil Drainage Curve

Eurasian Soil Science - The objectives of this research are prediction of soil drainage curve using Assouline and Or (2014) adjusted soil drainage model and comparison of the predicted results with...     

Evaluation of soil extractants to estimate available micronutrients under wheat‐field conditions

Abstract

Three extracting reagents were evaluated by correlation analyses to provide the best index of Zn, Cu, Mn and Fe availability to wheat (Triticum aestivum L.) plants growing under open field conditions. Twenty one soils were selected to obtain the widest range in properties of soils of the land wheat cultivated. The magnitude of the extractive power varied in the following order: 6NHCl ? EDTA + NH₄OA_C, pH4.65 > DTPA‐TEA, pH 7.3. The mild extractants, EDTA and DTPA, gave the same order of removal of micronutrients being Zn < Cu < Fe < Mn. The acid extractant was on the contrast more effective on Cu and Fe with respect to Zn and Mn, respectively. Wheat concentrations of Zn, Mn and Fe were significantly correlated to soil micronutrients. Highly significant relationships were found for Zn extracted by DTPA solution (r = 0.737***) and for Mn and Fe extracted by EDTA solution (r = 0.710*** and r = 0.564**). Plant Zn and Mn were also well predicted by the acid extraction. The absence of correlation for plant Cu vs. soil Cu occurred probably because of wheat concentrations almost constant, ranging from 5.0 to 8.0 mg/kg.     

Evaluation of some rice cultivars’ response to salinity stress using resistance indices

Parts of paddy fields in Mazandaran Province, northern Iran, are confronted with soil and water salinity. To screen proper rice cultivars, an experiment was performed with eight modified rice cultivars under four levels of irrigation water salinity (1, 2, 4 and 6 dS m^?1) with three replications, in Amol, northern Iran. The objective of the present study was the evaluation of eight screening indices for identifying salinity tolerance of these cultivars, so that suitable cultivars can be recommended for the cultivation with saline irrigation water in paddy fields. To evaluate the resistance of these cultivars to salinity stress, different indices were calculated. The results showed that Khazar cultivar was the most salt-sensitive cultivar in all salinity levels. In the irrigation salinity levels of 2 and 4 dS m^?1 Neda cultivar and in the level of 6 dS m^?1 Dasht cultivar were the most salt-resistant cultivars. In the two irrigation salinity levels of 4 and 6 dS m^?1, the mean productivity index was the most effective in the screening of salt-resistant cultivars. Harmonic mean, geometric mean productivity, stress tolerance index and mean productivity indices were found to be the best indices in screening resistant cultivars.     

Toxicity of three pesticides commonly used in Brazil to Pontoscolex corethrurus (Müller, 1857) and Eisenia andrei (Bouché, 1972)

The indiscriminate and excessive use of pesticides poses serious risks to humans and the environment, including soil biota. Ecotoxicological tests are useful to indicate the extent to which these chemicals are harmful and how and where their effects occur. Some of these tests were standardized by ISO (International Organization for Standartization) using the earthworm species Eisenia fetida and Eisenia andrei, both native to temperate climates. However, these species may be of lower relevance for soil ecotoxicological studies since they live in the litter and feed on fresh organic matter. The species Pontoscolex corethrurus, native to tropical regions, may be an alternative for more relevant ecotoxicological tests as it is an endogeic geophagous species. However, little is known of its sensitivity to pesticides. Therefore, avoidance and mortality tests were performed using E. andrei and P. corethrurus and three pesticides commonly used in Brazilian agriculture: carbendazim, carbofuran and glyphosate. The tests were conducted in tropical artificial soil (TAS). For carbendazim, the median avoidance concentration (AC₅₀) was 76.1 and 65.8 mg a.i. kg⁻¹ and the median lethal concentration (LC₅₀) 19.7 and 15.3 mg a.i. kg⁻¹ for E. andrei and P. corethrurus, respectively. For carbofuran, the AC₅₀ was 9.7 and 7.3 mg a.i. kg⁻¹ and LC₅₀ 13.5 and 9.3 mg a.i. kg⁻¹ for E. andrei and P. corethrurus, respectively. Concentrations applied in the field of these two pesticides have toxic effects on both species. Glyphosate showed no toxic effects for either species even at the highest concentration tested (47 mg a.i. kg⁻¹), although they displayed avoidance behavior at this concentration. The sensitivity of P. corethrurus appears to be similar to the standard species for the pesticides evaluated reinforcing the notion that E. andrei is a good test species. Nevertheless, further studies should be undertaken using other contaminants to confirm the similar sensitivity of both species and the relevance of E. andrei in ecotoxicological tests.     

A solid‐phase buffer technique to maintain low concentrations of phosphate in nutrient solutions

An inexpensive and mechanically simple technique has been developed to maintain realistically low P concentrations in nutrient solutions using a solid‐phase buffer. Phosphate is adsorbed on alumina in a PVC column, and the resulting alumina‐F is desorbed against nutrient solution circulated through the column. Kinetics of P adsorption and desorption indicate that the solid‐phase‐P has rapidly and slowly desorbing components and that buffering capacity is limited by desorption from the solid phase. The technique has been used to maintain F concentrations as low as 0.4 minol m^‐3 for 26 days in experiments with maize (Zea mays L.), and in solution cultures with prune (Prunus domestica L.) trees. Effects of P supply on P accumulation and P transport are discussed.     

Modified procedures for commercial adaptation of root iron‐reducing capacity as a screening technique

Abstract

Genotypic evaluation is critical to development of soybean [Glycine max (L.) Merr.] cultivars with genetic resistance to Fe‐deficiency chlorosis. Root Fe³⁺ reducing activity is correlated with genotypic resistance to Fe chlorosis measured in field nurseries, and thus may be a reliable method for identifying chlorosis‐resistat genotypes. However, to develop methods useful for large‐scale screening, several modifications of the previously published procedure for measuring root Fe³⁺ reducing activity were investigated. Several hydroponic experiments were conducted to test proposed modifications. It was determined that: (a) different genotypes may be grown together in the same nutrient solution without affecting Fe³⁺ reduction, (b) genotype separation is maximized by growth in CaCO₃ buffered solution (37.5 mg L^?1), (c) a labor‐intensive elongation step can be eliminated, and (d) denotype evaluation can be accomplished without introducing Fe into the hydroponic solutions. These refinements to the procedure should allow its adaptation and use in soybean breeding programs.     

Evaluation of Methods for Control of Ammonia Volatilization from Surface-Applied Nitrogen Fertilizers to Sugarcane Trash in North Queensland

Micrometeorological and microplot experiments were conducted in the field of freshly harvested green cane in Queensland,Australia.Results showed that high ammonia loss of fertilizer N could occur under relatively dry conditions when urea or commercial product of mixture of urea and muriate of potash were applied to the surface of sugarcane trash.The moisture content in the trash and the pH of fertilizer were two important factors controlling the processes of urea hydrolysis and ammonia volatilization.Most of the N in the soil was transformed to the nitratel-nitrite from after 70 days of fertilizer application.No significant leaching was found.Urea-free N fertilizers had higher N recoveries compared to urea-containing fertilizers.     

Molecular and cytogenetic characterization of a collection of bahiagrass (Paspalum notatum Flügge) native to Uruguay

Paspalum notatum is a subtropical grass present throughout America, and one of the main constituents of the natural grasslands in Uruguay. An apomictic autotetraploid (2n?=?4x?=?40) is the most frequent cytotype. The occurrence of sexual diploids (2n?=?2x?=?20) has also been reported as well as the occasional presence of apomictic triploids and pentaploids in Argentina. In this study, ISSR (inter simple sequence repeats) molecular markers were used to analyze the genetic variability of 210 P. notatum individuals from a collection from Uruguay. Cytometric analyses and chromosome counts were used to assess the ploidy level of the individuals. All plants from Uruguay analyzed were tetraploid. Intra- and inter-population variability was found both in genomic DNA content and at the genotypic level. Several multilocus genotypes were shared among individuals within populations and among populations over moderate geographical ranges, at the same time, very dissimilar genotypes were found within the same population. Part of the genetic variance among populations can be explained by a broader scale geographic structure which is partly coincident with the traditionally recognized grassland management regions. In spite of the apparently high degree of genetic admixture within populations, groups of related genotypes seem to follow a broader geographical structure in the area under study. These results suggest that an efficient collection strategy for this apomictically reproducing species should include carefully planned intra- and inter-population sampling. A broader scale regional sampling strategy should also be considered although further studies will be required to define genetic structure at this level.     

Evaluation of Crop Responses to Applied Fertilizer Phosphorus and Derivation of Optimum Recommendations using the Mitscherlich–Bray Equation

Abstract

In this article, the responses of three important crops (rice, wheat, and soybeans) to applied phosphorous (P) were examined and economically optimum P fertilizer recommendations using the Mitscherlich–Bray model were derived for the three crops at four locations in India. Crop‐yield responses were related to extractable P concentrations estimated by the Olsen method, employing a modification of Mitscherlich's equation. The parameters were considered reliable enough to use for the estimation of fertilizer recommendations at different fertilizer cost–price ratios (p) and marginal rate of return (R). The b parameter value explains how much soil P can substitute for fertilizer P. Thus, for each incremental unit of extractable P, fertilizer P could be reduced by 2.0, 2.9, 1.5, and 1.5 kg P/ha for rice (Periyar), rice (Bhubaneswar), wheat (Hisar), and soybean (Raipur), respectively. Optimum fertilizer rates for rice, wheat, and soybean were generated for different soil P fertility levels. There is also need for such information for other soils and crops.     

Is alternate wetting and drying irrigation technique enough to reduce methane emission from a tropical rice paddy?

Combination of a pre-season wet soil condition and rice straw incorporation just before transplanting, which is typical for a tropical rice double cropping, can induce a flash of methane (CH₄) emission shortly after the transplanting. The conventional practice of alternate wetting and drying (AWD) irrigation technique that typically starts at 21 days after transplanting (DAT) can hardly reduce this emission because the soil become methanogenic before the onset of AWD treatment. Field experiments were conducted in Central Luzon, Philippines, during the 2014–2017 dry rice seasons to examine the effects of the timing of rice straw/stubble incorporation on the efficacy of AWD in reducing the CH₄ emission. Two treatments of the timing of stubble incorporation were stubbles incorporated during the start of wet land preparation (S1) and stubbles incorporated during the dry fallow tillage (S2). For the water management, we compared two treatments: continuous flooding (CF) and AWD with – 15 cm threshold for irrigation. The AWD under S2 was implemented earlier at 10 DAT. We observed a significant interaction (p < 0.01) between effects of AWD and straw management on CH₄ emissions; the seasonal total CH₄ emission was reduced by AWD compared with CF by 73% under S2, while the reduction was <20% under S1. The AWD significantly (p < 0.05) increased the nitrous oxide (N₂O) emissions by 47 and 48% relative to CF under S1 and S2, respectively. The global warming potential (GWP, CH₄ + N₂O) and yield-scaled GWP were still substantially lower by 62 and 59%, respectively, in AWD than in CF under S2, but the reduction was not realized under S1 due to the relatively smaller CH₄ reduction and increased N₂O emission. The results confirm that pre-season aerobic stubble decomposition and earlier implementation of AWD enhanced AWD’s mitigation potential in reducing substantially the CH₄ emission from the tropical rice double-cropping system.     

Evaluation of the Accuracy of Diagnostic Tests From Repeated Measurements Without a Gold Standard

A model is presented to evaluate the accuracy of diagnostic tests from data from individuals that are repeatedly tested in time. Repeated measurements from three diagnostic tests for foot-and-mouth disease, applied to vaccinated and experimentally infected cattle, were analyzed. At any time the true disease status of the individuals was unknown, i.e., no gold standard was available. The model allows for correlation between repeated test results, in consequence of the underlying structure for the unknown true disease status, but also by the distribution of the test results conditional upon true disease status. The model also allows for dependence between the different diagnostic tests conditional upon true disease status. Prior information about the structure of the prevalence and the specificity of the tests was incorporated in a Bayesian analysis. Posterior inference was carried out with Markov chain Monte Carlo. Simulated data were analyzed to gain insight into the performance of the posterior Bayesian inference. The simulated data are typical for the expensive and, therefore, modestly sized infection experiments that are conducted under controlled conditions.     

Can commercial mulches be reservoirs of invasive earthworms? Promotion of ligninolytic enzyme activity and survival of Amynthas agrestis (Goto and Hatai, 1899)

Amynthas agrestis is an exotic, invasive earthworm in North America that has been associated with horticulture settings as well as damage to forest soil. An experiment was conducted to find out whether A. agrestis, an earthworm commonly found in mulches in Vermont, stimulates ligninolytic enzymes in the presence of commercial wood mulches. Mesocosms filled with a sandy loam soil were topped with either spruce, cedar or pine mulch. Half of the mesocosms received juvenile A. agrestis, the other half did not. After 7 weeks soils were analyzed for phenoloxidase and peroxidase activity. Most A. agrestis survived and developed into adults during the incubation period. Significantly greater phenoloxidase activity was detected in soils with A. agrestis than without earthworms. Mean (standard deviation) phenoloxidase activities in the presence of A. agrestis were 0.15 (±0.10), 1.14 (±0.46), 2.71 (±0.98) μmol g⁻¹ h⁻¹ for pine, spruce and cedar respectively, and 0.012 (±0.023), 0.25 (±0.25), 0.78 (±0.45) μmol g⁻¹ h⁻¹ in the absence of A. agrestis. There was significantly greater peroxidase activity for the pine and spruce treatment when earthworms were present. Mean peroxidase activities were 0.47 (±0.21), 0.94 (±0.29), 1.20 (±0.77) μmol h⁻¹ g⁻¹ soil for pine, spruce and cedar, respectively for soils with A. agrestis and 0.15 (±0.10), 0.37 (±0.10), 0.63 (±0.30) μmol h⁻¹ g⁻¹ soil in the absence of earthworms. The increased ligninolytic activity in combination with successful maturation of juveniles into adult A. agrestis suggests that mulch can be habitat for these invasive earthworms. This finding is supported by a survey of master gardeners in Vermont and New Hampshire 20% of whom reported to have seen these earthworms mainly in their gardens and mulched beds.