Use of the APSIM model in long term simulation to support decision making regarding nitrogen management for pearl millet in the Sahel

Soil fertility and climate risks are hampering crop production in the Sahelian region. Because experiments with only a few fertility management options on a limited number of sites and years cannot fully capture the complex and highly non-linear soil–climate–crop interactions, crop growth simulation models may suitably complement experimental research to support decision making regarding soil fertility and water management. By means of a long term (23 years) scenario analysis using the Agricultural Production Systems Simulator (APSIM) model, this study investigates millet response to N in view of establishing N recommendations better adapted to subsistence small-holder millet farming in the Sahel. Prior to this, the APSIM model was tested on a rainfed randomized complete block experiment carried out during the 1994 and 1995 cropping seasons, having contrasting rainfall conditions. The experiment combined, at three levels each, the application of cattle manure (300, 900 and 2700 kg ha^?1), millet residue (300, 900 and 2700 kg ha^?1) and mineral fertilizer (unfertilized control, 15 kg N ha^?1 + 4.4 kg P ha^?1 and 45 kg N ha^?1 + 13.1 kg P ha^?1) at ICRISAT Sahelian Center, Niger. The model suitably predicted plant available water PAW and the simulated water and nitrogen stress were in agreement with measurement (water) and expectation (N) regarding the fertilizer and rainfall conditions of the experiment. APSIM simulations were in satisfactory agreement with the observed crop growth except for the highest crop residue application rates (>900 kg ha^?1). For biomass and grain yield, the model performance was relatively good in 1994 but biomass yields were slightly overpredicted in 1995. The model was able to adequately reproduce the average trend of millet grain yield response to N inputs from manure and fertilizer, and to predict the overall observed higher grain yield in 1995 compared to 1994, despite the better rainfall in 1994. The 23-year, long term scenario analysis combining different application rates of cattle manure, millet residue and mineral fertilizer, showed that moderate N application (15 kg N ha^?1) improves both the long term average and the minimum yearly guaranteed yield without increasing inter-annual variability compared to no N input. Although it does imply a lower average yield than at 30 kg N ha^?1, the application of 15 kg N ha^?1 appears more appropriate for small-holder, subsistence farmers than the usual 30 kg N ha^?1 recommendation as it guarantees higher minimum yield in worst years, thereby reducing their vulnerability.     

Understanding the adoption of smartphone apps in crop protection

Precision Agriculture - There is a steady increase in smartphone apps available to improve farmers’ decision making with respect to crop protection. While current studies have focused on...     

Smartphone adoption and use in agriculture: empirical evidence from Germany

Precision Agriculture - Smartphone technology is promising for the future development of agriculture, as it can facilitate and improve many operational procedures and can also be combined with...     

Pharmacokinetics,pharmacodynamics, toxicology and therapeutics of mavacoxib in the dog: a review

Mavacoxib is a novel nonsteroidal anti‐inflammatory drug (NSAID), with a preferential action on the cyclooxygenase (COX)‐2 isoform of COX and a long duration of action. It is classified chemically as a member of the sulphonamide subgroup of coxibs. Mavacoxib is highly lipid but very poorly water soluble. In the dog, the pharmacokinetic (PK) profile comprises very slow body clearance, long elimination half‐life and a relatively large distribution volume. Biotransformation and renal excretion are very limited, and elimination occurs primarily by biliary secretion and excretion of unchanged drug in faeces. The PK profile of mavacoxib differs quantitatively between young healthy dogs (Beagles and mongrels) and clinical cases with osteoarthritis (OA). In OA dogs, mavacoxib exhibits a much longer terminal half‐life, associated principally with their greater median body weight compared with dogs used in preclinical studies. There is also some evidence of breed differences and a small effect of age on mavacoxib PK in the OA canine population. The pharmacodynamics (PD) of mavacoxib has been established: (i) in whole blood assays at the molecular level (inhibition of COX‐1 and COX‐2 isoforms); (ii) in preclinical models of inflammation and pain; and (iii) in clinical OA subjects treated with mavacoxib. The dosage schedule of mavacoxib for clinical use has been determined by owner and veterinary clinical assessments and is supported by integration of PK and PD preclinical data with clinical responses in canine disease models and in dogs with naturally occurring OA. The dosage regimen has been further confirmed by correlating levels of inhibition of COX isoforms in in vitro whole blood assays with plasma concentrations of mavacoxib achieved in OA dogs. In addition to the specific properties of mavacoxib, some general aspects of the PK and PD of other agents of the NSAID group, together with pathophysiological and clinical aspects of OA, are reviewed, as a basis for correlating with the safety and efficacy of mavacoxib in therapeutic use. Integration of PK and PD data suggests that the recommended dosage regimen of 2 mg/kg bw once for 14 days, followed by administration at monthly intervals, is optimal from both efficacy and safety perspectives and is further confirmed by clinical field studies.     

Grape Seed and Tea Extracts and Catechin 3-Gallates Are Potent Inhibitors of α-Amylase and α-Glucosidase Activity

This study evaluated the inhibitory effects of plant-based extracts (grape seed, green tea, and white tea) and their constituent flavan-3-ol monomers (catechins) on α-amylase and α-glucosidase activity, two key glucosidases required for starch digestion in humans. To evaluate the relative potency of extracts and catechins, their concentrations required for 50 and 90% inhibition of enzyme activity were determined and compared to the widely used pharmacological glucosidase inhibitor, acarbose. Maximum enzyme inhibition was used to assess relative inhibitory efficacy. Results showed that grape seed extract strongly inhibited both α-amylase and α-glucosidase activity, with equal and much higher potency, respectively, than acarbose. Whereas tea extracts and catechin 3-gallates were less effective inhibitors of α-amylase, they were potent inhibitors of α-glucosidase. Nongallated catechins were ineffective. The data show that plant extracts containing catechin 3-gallates, in particular epigallocatechin gallate, are potent inhibitors of α-glucosidase activity and suggest that procyanidins in grape seed extract strongly inhibit α-amylase activity.     

Nitrogen Sources and Adventitious Root Development in Eucalyptus globulus Microcuttings

In previous studies, it has been shown that nitrate supply may favor adventitious rooting in the rooting recalcitrant Eucalyptus globulus. Herein, the impact of various N sources on adventitious rooting and root branching in microcuttings of E. globulus was investigated. The positive effect of nitrate on adventitious root development was confirmed and extended to root branching. Urea yielded a rooting response comparable to that observed in presence of nitrate. Urease activity was observed, displaying two peaks: one at the root induction and another at the root formation step. The use of glutamic acid, glutamine or asparagine promoted higher root number, but yielded shorter roots. Rooted microcuttings derived from all nitrogen (N) sources were successfully acclimated to ex vitro conditions. The manipulation of N sources in adventitious rooting media can be a tool for improving new root density, length and branching in this species.     

Solid fraction of separated digestate as soil improver: implications for soil fertility and carbon sequestration

Journal of Soils and Sediments - This study investigated the C and N mineralisation potential of solid fractions (SFs) from co-digestated pig manure after P-stripping (P-POOR SF) in comparison with...     

Spectral vegetation indices selected for quantifying Russian wheat aphid (Diuraphis noxia) feeding damage in wheat (Triticum aestivum L.)

The effects of insect infestation in agricultural crops are of major economic interest because of increased cost of pest control and reduced final yield. The Russian wheat aphid (RWA: Diuraphis noxia) feeding damage (RWAFD), referred to as ??hot spots??, can be traced, indentified, and isolated from uninfested areas for site specific RWA control using remote sensing techniques. Our objectives were to (1) examine the use of spectral reflectance characteristics and changes in selected spectral vegetation indices to discern infested and uninfested wheat (Triticum aestivum L.) by RWA and (2) quantify the relationship between spectral vegetation indices and RWAFD. The RWA infestations were investigated in irrigated, dryland, and greenhouse growing wheat and spectral reflectance was measured using a field radiometer with nine discrete spectral channels. Paired t test comparisons of percent reflectance made for RWA-infested and uninfested wheat yielded significant differences in the visible and near infrared parts of the spectrum. Values of selected indices were significantly reduced due to RWAFD compared to uninfested wheat. Simple linear regression analyses showed that there were robust relationships between RWAFD and spectral vegetation indices with coefficients of determination (r ²) ranging from 0.62 to 0.90 for irrigated wheat, from 0.50 to 0.87 for dryland wheat, and from 0.84 to 0.87 for the greenhouse experiment. These results indicate that remotely sensed data have high potential to identify and separate ??hot spots?? from uninfested areas for site specific RWA control.