Farmers’ perceptions of earthworms and their role in soil

Farmers’ perceptions of earthworms were surveyed based on the criteria they use to identify them, i.e., use of common names, knowledge of morphological characteristics, presence in various land uses, soil layers, as well as direct and indirect use. A total of 39 farmers of the La Vieja River watershed in Colombia were interviewed and the data submitted to chi-square test and multiple correspondence analysis. Significant differences (p < 0.1) were found in farmers’ replies in relation to recognition and use of earthworms depending on gender, level of schooling, and age. According to the interviewees, earthworm abundance was highest in plantain and coffee crops, in places where harvest residues accumulate, and in soil layers from 0 to 20 cm depth. The topsoil was identified as the main area of recognition, which can be attributed to soil preparation tasks. Farmers differentiated earthworms by shape and color and in 97% of the cases, by size and how they react when captured. They recognized nine species and used several common names to differentiate them. Most (95%) farmers considered earthworms as soil quality indicators and many (38–49%) of them recognized their use for recreation and medicinal purposes and as important for soil organic matter decomposition. This study showed the value of local farmer knowledge for scientists as part of research aiming to facilitate communication between farmers and scientists and generate complementary means of addressing and interpreting natural processes and dynamics at the ecosystem level. It also highlights the need to draw from farmers’ perceptions in informal education processes and to link the contributions of scientists to traditional knowledge in order to consolidate proposals related to biodiversity conservation and use in rural development programs.     

Earthworm ecosystem service and dis-service in an N-enriched agroecosystem: Increase of plant production leads to no effects on yield-scaled N2O emissions

Earthworms can enhance plant productivity by promoting nitrogen (N) mineralization in N-limited agroecosystems and may also enhance the risk of N₂O emissions and ${{\text{NO}}_3}^{-}–\text{N}$ leaching in N-enriched agroecosystems. However, direct evidence demonstrating the enhancement by earthworms of N₂O emissions and ${{\text{NO}}_3}^{-}–\text{N}$ leaching in the field is scarce, particularly in intensively managed systems. In addition, the interaction of earthworm feeding strategies and organic amendment may profoundly modulate N cycling. We examined these impacts using two earthworm species with distinct ecological strategies (epigeic Eisenia foetida and endogeic Metaphire guillemi) in combination with two manure application methods (surface mulch and incorporation into the soil) in a field experiment. Our results demonstrated that earthworm addition significantly increased the crop yield by 18%–47% and cumulative N₂O emissions by 19%–25% largely regardless of earthworm species and manure application methods, respectively. However, earthworms did not significantly increase the leachate ${{\text{NO}}_3}^{-}–\text{N}$ concentration. Earthworm-induced N₂O emissions were primarily attributed to increased soil N availability (${{\text{NO}}_3}^{-}–\text{N}$ and microbial biomass N) and carbon (C) availability (dissolved organic C). In contrast, a stepwise regression revealed that an earthworm-promoted soil macroaggregation exerted negative effects on N₂O emissions. Irrespective of earthworm species and manure application methods, earthworms had no stimulatory effects on the yield-scaled N₂O–N because the promotion of crop productivity counteracted the extent of N₂O increase. In conclusion, understanding the trade-off between earthworm services and dis-services will contribute to the development of environmentally justified soil management by allowing the full utilization of biological resources.     

Decision support framework for assessment of non-point-source pollution of groundwater in large irrigation projects

Agriculture is the main non-point polluter of groundwater in irrigated areas as fertilizers and other agrochemicals are the main contaminants in the water that drains out of the root zone to recharge the aquifer. Nitrates from fertilizers, dissolved in percolation losses from rice fields, are the source of pollution considered. The concentration of nitrates in the percolated water depends on the distributed field water and nitrogen balances over the area. Its concentration in the groundwater depends on the total recharge, pollution loading, groundwater flow and solute transport within the aquifer. The development and application of a GIS based decision support framework that integrates field scale models of these processes for assessment of non-point-source pollution of groundwater in canal irrigation project areas is presented. The GIS is used for representing the spatial variations in input data over the area and map the output of the recharge and nitrogen balance models. The latter are used to provide the spatially distributed recharge and pollutant load inputs to the distributed groundwater flow and transport models, respectively. Alternate strategies for water and fertilizer use can be evaluated using this framework to ensure long-term sustainability of productive agriculture in large irrigation projects. The development and application of the framework is illustrated by taking a case study of a large canal irrigation system in India.     

Seed germination response of cuphea to temperature

Cuphea (Cuphea viscosissima Jacq. × C. lanceolata W.T. Aiton; PSR23) is a potential new oilseed crop. Its oil is high in medium-chain fatty acids that are suitable for detergent/cleaner applications and also for cosmetics. The objective of this study was to determine the critical temperatures for cuphea seed germination. To determine the base, maximum, and optimum temperatures for seed germination, mature cuphea seeds were harvested from plants grown at Prosper, ND, in 2004, 2005, and 2006. Seeds were germinated on a temperature-gradient bar varying between 5 and 35 °C. Cumulative germination was calculated for each temperature treatment. Base temperature (T_b) and optimum temperature (T_o) were estimated from the third-order polynomial temperature-response functions for each year. In addition, germination rate per day was used in a linear model to estimate the base temperature below which germination rate was equal to zero (T_b), and the maximum temperature above which germination was equal to zero (T_m). The optimum temperature (T_o) was calculated as the intercept of sub-optimal and supra-optimal temperature-response functions. Through the third-order polynomial temperature-response functions and the sub-optimal/super-optimal intercept approaches, we were able to generate six estimates for each critical value. Estimates of the base temperature for cuphea seed germination ranged between 3.3 and 11 °C, with the most reliable estimates between 6 and 10 °C, similar to many warm-season crops such as corn (Zea mays L.) and sorghum (Sorghum bicolor L.). The optimum temperature for cuphea seed germination ranged between 18.5 and 24 °C with a mean value of 21 °C. The maximum temperature for seed germination ranged 33–38 °C. On this basis, a cuphea planting date after 20 May is recommended for east-central North Dakota.     

MALDI-Qq-TOF-MS and transient gene expression analysis indicated co-enhancement of β-1,3-glucanase and endochitinase by tMEK2 and the involvement of divergent pathways

A mitogen-activated protein kinase (MAPK) pathway has been demonstrated as a key pathway in plant defense against pathogen attacks. With proteomics approaches, we specifically studied activation events downstream of a MAPK kinase, tMEK2, in tomato. Overexpression of a constitutively activated tomato MAPK kinase gene (tMEK2^MUT) enhanced resistance of transgenic tomato lines to the virulent bacterial pathogen Pseudomonas syringae pv. tomato. Pathogenesis-related genes, PR1b1, β-1,3-glucanase, and endochitinase were up-regulated by tMEK2^MUT. Two-dimensional electrophoresis and matrix-assisted laser desorption/ionisation-time-of-flight-mass spectrometry analysis of total soluble leaf proteins indicated that β-1,3-glucanase and endochitinase are among the up-regulated proteins in these transgenic plants. Co-expression studies using a transient gene expression system have indicated that β-1,3-glucanase and endochitinase genes up-regulated by tMEK2^MUT were down-regulated by different specific phosphatases through dephosphorylation of certain downstream signaling molecules. Our observations indicate that increased products of β-1,3-glucanase and endochitinase genes downstream of tMEK2 may play an important role in achieving disease resistance.     

Identification and antimicrobial activity of two alkaloids from traditional Chinese medicinal plant Tinospora capillipes

Two antimicrobial alkaloids, palmatine and jatrorrhizine, were isolated from tubers of traditional Chinese medicinal plant Tinospora capillipes using activity-guided isolation method and chromatography. Their antimicrobial activity was determined in vitro. The results showed that palmatine and jatrorrhizine had inhibitory activity against plant pathogens Colletotrichum gloeosporioides, Fusarium oxysporum f. sp. niveum, Mycosphaerella sentina, Pestalotia mangiferae, Cercospora kaki, Gymnosporangium haraeanum, Rhizoctonia solani and Colletotrichum graminicola, with the EC₅₀ values of 0.0348-0.8356 g L⁻¹ and 0.0240-0.8649 g L⁻¹, respectively. Palmatine and jatrorrhizine also exhibited inhibition against animal pathogens Bacillus cereus, Bacillus megaterium, Bacillus subtilis, Staphyloccocus aureus, Staphylococcus epidermidi, Micrococcus lysodeikticus, Proteus vulgaris, Salmonella typhi and Escherichia coli, with the MIC values of 0.1-0.8 g L⁻¹ and 0.1-0.6 g L⁻¹, respectively. These results suggested that palmatine and jatrorrhizine showed relatively broad spectrum antimicrobial activity against plant and animal pathogens.     

Application of eco-physiological quotients (qCO2 and qD) on microbial biomasses from soils of different cropping histories

Metabolic quotients for CO₂C (qCO₂C) and microbial-C-loss (qD) were studied on soil microbial communities under long-term monoculture (M) or continuous crop rotations (CR). Under defined laboratory conditions the mean qCO₂C (unit CO₂C unit⁻¹ C_mic h⁻¹) of different microbial biomasses from 17 M systems amounted to 1.097 μg CO₂qCO₂CC as compared to 0.645 μg CO₂C of microbial biomasses from 19 CR systems. The 1.7 times higher CO₂C release per unit biomass and time of microbial biomasses from M systems was significantly different at the P =0.001 level.In addition, microbial C-loss in samples from M or CR plots was followed for 5 weeks. Again, mean qD per unit microbial biomass and time was 1.6 times higher (P = 0.01) for microbial biomasses from M systems (0.301 μg C, 14 soils) when compared with CR systems (0.188μg C, 14 soils).These differences were not related to soil texture, C_org or pH of these soils. The effects of environmental influences (soil management) on the microbial pool in terms of a changing energy demand are discussed.     

Use of soil physical characteristics from laboratory measurements or standard series for modelling unsaturated water flow

Soil physical characteristics are important input parameters for simulation modelling of unsaturated flow in soils and associated solute flow. The determination of soil water retention and hydraulic conductivity curves in the laboratory is laborious and expensive. For modelling studies that require characteristics for many soil horizons, such as regional studies or scenario studies, it may be impossible to measure all the necessary characteristics. An alternative would be to use characteristics inferred from readily available soil data by class-pedotransfer functions. In this study such a comparison was made for six sites on sandy soils in the Netherlands using the soil-water model SWACROP with soil physical characteristics from either laboratory measurements or from a standard series as input. For this the simulated pressure head values and moisture content values were compared with measured values at eight different depths using statistical criteria. Furthermore two functional criteria, i.e. the number of workable days and number of days with possible drought, were inferred from simulated pressure head values and again the different results were compared. It was found that simulation results were not significantly different, implying that standard series or class-pedotransfer functions could be used in studies like these for simulating the unsaturated water flow regime in sandy soils on field/farm level or regional level. Differences for specific criteria for individual sites were sometimes substantial and in such cases (at field level) it will make a difference which soil physical characteristics are used.     

Old tall durum wheat cultivars are suited for dual-purpose utilization

The lateness, tallness and high vigour of old tall durum wheat cultivars could be advantageous for dual-purpose use and their high propensity for lodging should be reduced by grazing. A 3-year field trial was performed in Sardinia, Italy, in a typical Mediterranean environment. Crops of the durum wheat cultivar Senatore Cappelli were sown in October, and grazing was simulated by clipping half of the plots at the terminal spikelet stage of development. The forage biomass derived from clipping varied greatly between seasons (from 0.8 to 3.3 t ha⁻¹ dry matter) in response to the notable inter-seasonal variability in weather conditions. Cultivar Senatore Cappelli showed good recovery following clipping, with the ability to attain almost complete radiation interception well before anthesis. The high number of leaves that emerged after clipping might have contributed to this good recovery. Nevertheless, clipping reduced the dry matter produced by anthesis (16 t ha⁻¹ in clipped compared to 21 t ha⁻¹ in unclipped crops) as well as the final dry matter (DM_MAT) (19 t ha⁻¹ in clipped compared to 23 t ha⁻¹ in unclipped crops), although these differences disappeared when the clipped biomass was included. The lower lodging observed at anthesis in the clipped (21%) compared with unclipped crops (63%) likely reduced the difference between treatments. The lower DM_MAT of clipped treatments was reflected in a lower grain yield (GY) (3.4 t ha⁻¹ vs 4.2 t ha⁻¹ in the unclipped treatment). Clipping did not affect the amount of nitrogen present in the biomass, nitrogen uptake efficiency or radiation use efficiency. GY reduction after clipping was mediated by the reduction in spikes m⁻² and kernels m⁻² (KNO). Spike fertility was not affected by clipping, because the same amount of radiation was available for each spike (about 1 MJ). The period with reduced ground cover after clipping was reflected in an increased evaporation and reduced transpiration, which did not alter the total water used and increased the transpiration efficiency in terms of DM_MAT.Old tall durum wheat cultivars manifested good suitability for dual-purpose use in environments with low attainable yields because their low grain yield potential contributed to reducing the negative effects of clipping on GY. Their high straw yield and kernel protein percentage represented an advantage with respect to semi-dwarf cultivars.