Phosphorus fractions and dynamics as affected by land-use changes in the Central Mexican highlands

Land-use change from forest to agriculture in the volcanic ash-derived soils of Mexico has increased over recent decades. It is likely that land uses and management practices, particularly fertilizer use have affected phosphorus (P) distribution and availability. The objective of this study was to evaluate the effects of land-use types (native forest and maize mono-cropping), and the related P addition, on the forms and distribution of soil P and their isotopic exchangeability. An Andisol, sampled from a cropping site, along with the contiguous area under native forest was treated with ³²P-labelled potassium phosphate (KH₂³²PO₄). The soil samples were extracted after incubation times of 7, 21, 35 and 49 days. Phosphorus content and ³²P recovery in fractions sequentially extracted were assessed for each incubation time. Total soil P was dominated by inorganic fractions (79 to 86%) in both land-use types. Resin-Pi, bicarbonate extractable inorganic P (Bic-Pi) and sodium hydroxide extractable inorganic P (NaOH_0.1-Pi) were all raised with P addition. However, the proportion of organic P fraction was reduced under cropped soil. The recovery of ³²P in soils with P addition indicates that resin-Pi, Bic-Pi and NaOH_0.1-Pi comprised nearly all the exchangeable P. In native soils with no P addition, more than 19% of the ³²P was recovered in Bic-Po and NaOH_0.1-Po forms. This finding indicates that organic P cycling is crucial when soil Pi reserves are presented in an inadequate amount. Ecologically based management has to be designed for replenishment and succeeding maintenance of soil organic P compounds to increase sustainable agricultural production.     

Waterlogging tolerance of pea at germination

Peas (Pisum sativum L.) are exposed to waterlogging at germination when grown as relay in rice‐based cropping. Ninety‐one germplasm accessions were evaluated in relay (sown in waterlogged soil), and subsequently 10 diverse genotypes compared under relay and sole cropping (conventional tillage sowing) over two seasons in Bangladesh. Contrasting genotypes, BM‐3, NL‐2 and Kaspa, were further evaluated in three waterlogging treatments (drained control, 4 and 8 days waterlogging) in the glasshouse. Conspicuous variation in waterlogging tolerance at germination was observed in the field and confirmed under controlled conditions. In relay sowing in 2011, emergence of a few genotypes was affected by waterlogging. In 2012, emergence in relay was severely affected (12 plants/m²) compared to sole sowing (37 plants/m²). Among genotypes BM‐3 had 6 plants/m² emerge, which all subsequently died, in contrast to NL‐2 in which emergence was 13 plants/m² with all plants surviving. In the glasshouse, there was 14% emergence in BM‐3, 40% in NL‐2 and 55% in Kaspa after 8 days of waterlogging. Such marked differences in waterlogging tolerance at germination in the model pea are the first reported and illustrate prospects for selection to improve adaptation to relay sowing in South Asia.     

Water Use and Seed Yield of Horsegram Under Different Moisture Regimes and Mulches in Semi-Arid Region of Eastern India

In a two years field study on effect of irrigation at vegetative and flowering stages occurring at 40 and 60 days after sowing, respectively alongwith straw mulch ca. 5 t/ha were found to have beneficial effect on growth, yield attributes and seed yield of horsegram ( Dolichos biflorus Roxb.). Application of mulches significantly increased pods/plants, seeds/pod, test weight and seed yield and maintained better soil moisture during crop growth in semi-arid lateritic region of Indian sub-tropics. Mulches proved useful to conserve more moisture in soil profile and thereby increased the water use efficiency of the crop; straw mulch was found superior to leaf mulch.     

Substrate type,temperature, and moisture content affect gross and net N mineralization and nitrification rates in agroforestry systems

Accurate prediction of soil N availability requires a sound understanding of the effects of environmental conditions and management practices on the microbial activities involved in N mineralization. We determined the effects of soil temperature and moisture content and substrate type and quality (resulting from long-term pasture management) on soluble organic C content, microbial biomass C and N contents, and the gross and net rates of soil N mineralization and nitrification. Soil samples were collected at 0–10 cm from two radiata pine (Pinus radiata D. Don) silvopastoral treatments (with an understorey pasture of lucerne, Medicago sativa L., or ryegrass, Lolium perenne L.) and bare ground (control) in an agroforestry field experiment and were incubated under three moisture contents (100, 75, 50% field capacity) and three temperatures (5, 25, 40 °C) in the laboratory. The amount of soluble organic C released at 40 °C was 2.6- and 2.7-fold higher than the amounts released at 25 °C and 5 °C, respectively, indicating an enhanced substrate decomposition rate at elevated temperature. Microbial biomass C:N ratios varied from 4.6 to 13.0 and generally increased with decreasing water content. Gross N mineralization rates were significantly higher at 40 °C (12.9 g) than at 25 °C (3.9 g) and 5 °C (1.5 g g^–1 soil day^–1); and net N mineralization rates were also higher at 40 °C than at 25 °C and 5 °C. The former was 7.5-, 34-, and 29-fold higher than the latter at the corresponding temperature treatments. Gross nitrification rates among the temperature treatments were in the order 25 °C >40 °C >5 °C, whilst net nitrification rates were little affected by temperature. Temperature and substrate type appeared to be the most critical factors affecting the gross rates of N mineralization and nitrification, soluble organic C, and microbial biomass C and N contents. Soils from the lucerne and ryegrass plots mostly had significantly higher gross and net mineralization and nitrification rates, soluble organic C, and microbial biomass C and N contents than those from the bare ground, because of the higher soil C and N status in the pasture soils. Strong positive correlations were obtained between gross and net rates of N mineralization, between soluble organic C content and the net and gross N mineralization rates, and between microbial biomass N and C contents.     

An integrated water trading-allocation model, applied to a water market in Australia

Temporary water trading is an established and growing phenomenon in the Australian irrigation sector. However, decision support and planning tools that incorporate economic and biophysical factors associated with temporary water trading are lacking. In this paper the integration of an economic trading model with a hydrologic water allocation model is discussed. The integrated model is used to estimate the impacts of temporary water trading and physical water transfers. The model can incorporate economic and biophysical drivers of water trading. The economic model incorporates the key trade drivers of commodity prices, seasonal water allocations and irrigation deliveries. The hydrologic model is based on the Resource Allocation Model (REALM) framework, which facilitates hydrologic network simulation modelling. It incorporates water delivery system properties and operating rules for the main irrigation and urban centres in a study area.The proposed integration method has been applied to a case study area in northern Victoria, Australia. Simulations were conducted for wet and dry spells, a range of commodity prices and different irrigation distribution system configurations. Some example analyses of scenarios incorporating water trading were undertaken. From these analyses potential bottlenecks to trade that constrain the economic benefits from temporary water trading were identified. Furthermore, it was found that in certain areas of the system, trading can make impacts of long drought spells worse for water users, e.g. irrigators. Thus, the integrated model can be used to quantify short-term and long-term third party impacts arising from temporary water trading. These findings also highlight the need to link “paper trades” (estimated by economic models) to physical water transfers (estimated by biophysical models).     

Estimation of the rootzone depth above a gravel layer (in wild blueberry fields) using electromagnetic induction method

Wild blueberry (Vaccinium angustifolium Ait.) fields in the north east Canada are naturally grown in a course textured thin layer of soil and below this layer is a soilless layer of gravel. The root zone depth of this crop varies from 10 to 15 cm. Investigating the depth to the gravel layer below the course textured soil is advantageous, as it affects the water holding capacity of the root zone. Water and nutrient management are the two primary determinants of crop yield and the amount of leaching. The objective of this study was to estimate the depth to the gravel layer using DualEM-2 instrument. A C++ program written in Visual Studio 2010 was used to develop mathematical models for estimating the depth to the gravel layer from the outputs of DualEM-2 sensor. Two wild blueberry fields were selected in central Nova Scotia, Canada to evaluate the performance of DualEM-2 instrument in estimating the rootzone depth above the gravel layer. The mid points of squares created by grid lines were used as the sampling points at each experimental site. The actual depth to the interface was measured manually at selected grid points (n = 50). The apparent ground conductivity (EC_a) values of DualEM-2 were recorded and the depth to the interface was estimated for the same sampling points within the selected fields. The fruit yield samples were also collected from the same grid points to identify the impact of the depth to the gravel layer on crop yield. After calibrations, comprehensive surveys were conducted and the actual and estimated depths to the interface were established. The interpolated maps of fruit yield, and the actual (z_in) and estimated (\( {\text{z}}_{\text{in}}^{*} \)) depths to the interface were created in ArcGIS 10 software. Results indicated that the z_in was significantly correlated with \( {\text{z}}_{\text{in}}^{*} \) for the North River (R ² = 0.73; RMSE = 0.27 m) and the Carmel (R ² = 0.45; RMSE = 0.20 m) sites. Results revealed that the areas with shallow depth to the gravel layer were low yielding, indicating that the variation in the depth to the gravel layer can have an impact on crop productivity. Non-destructive estimations of the depth to the gravel layer can be used to develop erosion control strategies, which will result in an increased crop production.     

Effect of a saponin-based surfactant and aging time on ruminal degradability of flaked corn grain dry matter and starch

The objectives of this study were to investigate the effect of a saponin-based surfactant, Grain Prep surfactant (GP), and hot flake aging time on starch characteristics and ruminal DM and starch degradability of steam-flaked corn grain. In 2 experiments, the moisture content of incoming corn was automatically adjusted using the Grain Prep Auto Delivery System to 19.8% (Exp. 1) and 18.5% (Exp. 2). The application rate of GP was 22 mg/kg (as-is basis). Control corn was treated with water alone. Processed corn in Exp. 2 was stored in insulated containers for 0, 4, 8, or 16 h. Flaked corn samples were incubated in the rumen of lactating dairy cows for 0, 2, 4, 6, 16, or 24 h. In Exp. 1, GP increased, compared with the control, the soluble fraction and effective degradability (ED) of DM by 17.2 and 8.6%, respectively. The ED of cornstarch was increased by 6.7%. In Exp. 2, the concentration of soluble DM and starch were increased by GP by 15 and 24% compared with the control. The ED of DM and starch were also increased by 3 and 4%, respectively. No differences in gelatinization temperatures were observed due to treatment, except that GP-treated grain had a slightly greater mean gelatinization enthalpy in Exp. 2. In a pilot study, DM degradability parameters were not affected by germination of the corn kernels. Aging of the hot flakes for up to 16 h resulted in a quadratic decrease in DM and starch ruminal degradability. The aging process affected starch gelatinization enthalpy values of flaked grain in a manner opposite to that observed for ruminal DM and starch degradation. This phenomenon was most likely explained by increased starch intramolecular associations or crystallinity associated with starch annealing, or both. This study confirmed our previous observations that Grain Prep surfactant increases flaked corn DM and starch degradability in the rumen. Because the rate of degradation was not affected by the surfactant, the increase in degradability was attributed mainly to increases in DM and starch solubility.     

A study of health and productivity of traditionally managed cattle in Zambia

A three-tiered survey was devised comprising a detailed questionnaire, a serological survey and a sentinel herd scheme for disease surveillance. The survey was carried out in the traditional farming sector in 7 districts of Zambia to obtain background information on cattle management and productivity, data on the prevalence of tick-borne and other disease problems in these areas and to monitor changes in individual herds.In the questionnaire survey, 288 farmers were interviewed. They owned a total of 15 360 head of cattle, representing approximately one percent of the national herd. Mean herd sizes ranged from 31 to 114 for each district. Mean calving percentages were 44–80%. Average national offtake from these herds was 10%. Calf mortality rates ranged from 4 to 32%, while adult yearly mortality rates ranged from 4 to 16%. Factors affecting the regional variation of these figures are discussed.     

Comparative Performance of Copper and Silver Coated Stretchable Fabrics

The present work described the development of multifunctional, electrically conductive and durable fabrics by coating of silver and copper particles using a dipping-drying method. The particles were directly grown on fabric structure to form electrically conductive fibers. Particles were found to fill the spaces between the microfibers, and were stacked together to form networks with high electrical conductivity. The electrically conductive fabrics showed low resistance with high stretch ability. The utility of conductive fabrics was analyzed for electromagnetic shielding ability over frequency range of 30 MHz to 1.5 GHz. The EMI shielding was found to increase with increase in concentration of copper and silver particles. Furthermore, the heating performance of the copper and silver coated fabric was studied through measuring the change in temperature at the surface of the fabric while applying a voltage difference across the fabric. The maximum temperature (119°C for silver and 112°C for copper) were obtained when the applied voltage was 10 V. Moreover, the role of deposited particles on antibacterial properties was examined against pathogenic bacteria such as Staphylococcus aureus and Escherichia coli. At the end, the durability of coated fabrics was examined against several washing cycles. The fabrics showed good retention of the particles, proved by small loss in the conductivity of the material after washing.     

Growth and Physiological Performance of Aerobic and Lowland Rice as Affected by Water Stress at Selected Growth Stages

Aerobic rice technology is still new in Malaysia, and information regarding MARDI Aerob 1 (MA1), the first local aerobic rice variety, is still lacking. Therefore, comparative studies were carried out to determine the physiological performance of aerobic rice variety MA1 and lowland rice variety MR253 under water stress given at the panicle initiation, flowering and ripening stages. This experiment was arranged in a randomized complete block design. Stomatal conductance (g_s), chlorophyll a fluorescence (F_v/F_m), leaf relative water content (leaf RWC), and soil moisture content (SMC) as well as yield component parameters such as panicle number, grain yield and 100-grain weight were measured. Results revealed that g_s and leaf RWC for both varieties decreased with depletion of SMC. The correlation study between the physiological parameters and SMC indicated that F_v/F_m was not affected by water stress, regardless of varieties. The yield components (panicle number, grain yield and 100-grain weight) for both varieties greatly decreased when water stress was imposed at the panicle initiation stage. This study showed that the panicle initiation period was the most sensitive stage to water stress that contributed to a substantial reduction in yield for both varieties. Under the aerobic condition (control), MR253 produced higher panicle number, 100-grain weight and yield than MA1. Although MR253 is bred for lowland, it is well adapted to aerobic condition.