Feed the crop, not the soil! : Explaining variability in maize yield responses to nutrient applications in smallholder farms of western Kenya

Crop productivity intensification in smallholder farming systems of sub-Saharan Africa (SSA) is urgently required to improve food self-sufficiency. Increased fertilizer use can address nutrient deficiencies that limit crop productivity in SSA. There is however large uncertainty in crop yield responses to fertilizer applications on farmer fields. This uncertainty has been linked to strong heterogeneity in soil fertility between and within farms. Fertilizer recommendations that account for this spatial heterogeneity are therefore required to better advise farmers, reduce investment and environmental risks for sustainable crop productivity intensification. The main objective of this study was to better understand and explain patterns of maize yield and yield responses to fertilizer applications under heterogenous fertility conditions in smallholder farming systems. This would allow for improved targeting of fertilizer applications, and enable better prediction of expected crop yield response to fertilizer use. A series of on-farm experiments assessing maize yield response to fertilizer application under variable soil fertility conditions were established on 23 farmers’ fields in Siaya, western Kenya across multiple seasons. Prior to experiment establishment, farmers were extensively interviewed to obtain information on past crop and nutrient management practices in selected fields. The experiment used was comprised of nutrient omission trials (NOTs) on farmer fields in Siaya to assess patterns of maize yield response to fertilizer applications of 150 kg ha-1 nitrogen (N), 40 kg ha-1 phosphorus (P) and 60 kg ha-1 potassium (K). In Phase 1, plots with treatments including control, PK, NK, NP and NPK were repeated for 7 consecutive seasons in the same plots. In Phase 2 of the experiment, a second set of NOTs including PK, NK, NP and NPK were established in every plot on 6 fields that were previously part of Phase 1. On 13 other fields from Phase 1, all plots received NPK in Phase 2. Yields and above ground biomass were measured every year, soil samples were taken in 2013, 2014, 2016 and 2018 and plant samples were taken in 2016 and 2018. Spatial-temporal patterns in yield and yield responses were studied and compared with soil and farmer characteristics. Yield response to soil nutrient supply was studied with the QUEFTS model, and the RC-P model was used to study fate of fertilizer P. Nutrient balances were calculated. The frequency and magnitude of maize yield response to fertilizer N, P and K varied strongly over space and time, yet observed patterns were not adequately explained by soil chemical parameters or texture. Fertilizing with N, P, and K substantially reduced observed spatial-temporal variability in maize yield response, and resulted in consistently enhanced maize yields. All fields were responsive to N, most fields to P and only 7 to K. On average, NPK yields were about 5 to 5.5 tons ha-1 in the short- and long rainy seasons respectively. Application of only NP or NK resulted in strongly declining yields within a few seasons, with large differences between farms in resilience of soil P and K stocks. Based on observed spatial-temporal patterns, we concluded that blanket fertilizer recommendations in such farming systems result in low fertilizer use efficiencies. We further concluded that current methods for soil analysis do not adequately explain the observed variation in maize yield response to application of N, P and K fertilizers under the highly variable soil fertility conditions encountered in smallholder farming systems. Accounting for past manure application in Phase 1 of the experiment improved our ability to explain the variation in maize yield response to fertilizer application. Mean maize yield response to N, P and K application was 2.8, 1.1 and 0.6 t ha-1 in fields with animal manure previously applied, and 2.3, 3.0 and 1.6 t ha-1 in farms without past manure applications over 7 cropping seasons. Differences in maize yield response in fields with and without past manure applications were mainly related to enhanced soil phosphorus (P) and potassium (K) supply, and larger recovery of applied nitrogen (N) in fields with manure previously applied. Based on these findings, we concluded that the strong influence of past animal manure application on yield response to fertilizer applications merits the inclusion of past manure application as a co-variate in analysis of yield response data from smallholder cropping systems of SSA. The Quantitative Evaluation of the Fertility of Tropical Soils (QUEFTS) model did not adequately estimate crop yield responses to fertilizer applications under variable soil fertility conditions. This was linked to poor estimation of soil N, P and K supply based on current relationships for potential soil nutrient supply in the QUEFTS model. In particular, soil organic carbon (SOC) and P-Olsen were poor indicators of crop N and P uptake from the soil. Maize grain yield in unfertilized control treatment plots provided better estimates of potential soil N, P and K supply, resulting in improved predictions of maize yield response to fertilizer applications. These findings suggest that the standard soil parameters analysed do not accurately inform on the soil fertility status of the field and are of little use for smallholder farmers. Improved relations for estimation of potential soil nutrient in QUEFTS are required for better prediction of expected maize yield response to fertilizer application under variable soil fertility conditions. Maize crops in strongly nutrient-depleted soils responded strongly to balanced NPK fertilization, with yields comparative to long-term means within three seasons. Placement of P fertilizer strongly improved recovery, reducing the need for larger soil P stocks on soils that will typically develop a large insoluble P pool under P fertilization. The RC-P model provided insights in long-term recovery of P and could describe the observed P uptake patterns reasonably well. We concluded that strongly nutrient depleted tropical soils such as those in Siaya with high clay contents that are typical for western Kenya, do not require prior investments to rebuild nutrient stocks and soil organic matter to substantially increase crop yields to 5-5.5 t ha-1. This has important implications for crop productivity intensification in SSA as a large proportion of soils under cultivation are strongly nutrient depleted, and earlier approaches have suggested the need for costly and capital intensive soil fertility replenishment. Results in this thesis clearly demonstrate that sustainable intensification of crop productivity on smallholder farms of SSA is very well possible on all fields under good management, even when soils are strongly nutrient depleted. However, the need for P and K fertilizers and amounts applied should be tailored to specific field conditions to reduce farmer costs in the short term. Accounting for past farm management and assessment of current yields under minimal or no fertilizer applications provides a means for improved targeting of fertilizer applications at the farm level. In the long term, farmers should aim for balanced fertilization to prevent mining of soil stocks. Simplified decision support tools that use field level information to develop improved estimates of fertilizer N, P and K requirements based on refined relationships between soil nutrient supply, nutrient uptake and yield, are required to derive fertilizer recommendations in future.</p

Rural WASH project in Zimbabwe: monitoring and feedback mechanism for accelerating progress

A large scale Rural WASH Project is being implemented in 33 districts of Zimbabwe since June 2012. Failure of formal and routine monitoring mechanism during the initial phase of implementation led to development of innovative, rigorous but a very simple monitoring, feedback and reporting mechanism. This was built and integrated into the routine monitoring and reporting system of the implementing partners without creating additional burden. This mechanism proved to be extremely successful in tracking the progress at logframe/national, provincial/regional, implementing partner, district and indicator level on monthly basis. The mechanism was linked to development of corrective action plans at various levels aimed at accelerating progress. Each month a comprehensive graphical report is prepared and shared at national, provincial, and district levels with all stakeholders including donors. The overall progress on the project so far is well on track which was substantially behind before initiation of this monitoring mechanism

Treatment of shigella infections: why sulfamethoxazole-trimethoprim, tetracyclines and ampicillin should no longer be used

Background: Bloody diarrhoea results in high morbidity and mortality especially in developing countries with shigellosis being the main cause of acute bloody diarrhoea. The use of appropriate antimicrobial agents in the treatment of acute diarrheal disease shortens the duration of illness and bacterial shedding leading to a reduction in morbidity and mortality. Treatment options for many infections are becoming limited due to globally emerging antibiotic resistance. Globally, resistance of shigella species to trimethoprim-sulfamethoxazole (TMP-SMX), tetracyclines and ampicillin has been reported with subsequent recommendations of not using these antimicrobial drugs for empirical therapy of acute bloody diarrhoea.Objective: To establish the antimicrobial susceptibility patterns and antimicrobial drug use for treatment of shigella species in patients with acute bloody diarrhoea.Design: A hospital based case control study.Setting: Six health facilities, three in Kilifi County and three in Nairobi County.Subject: A total of 284 stool specimens were collected from patients who fitted the standard cases definition for acute bloody diarrhoea.Results: Eighty (28.2%) bacterial isolates were recovered from 284 stool samples collected from cases presenting with acute bloody diarrhoea of which 67 (83.8%) were Shigella species, nine (11.3%) were Enteroinvassive Escherichia coli isolates, three (3.8%) were Salmonella Typhi and one (1.3%) were Yersinia enterocolitica. Shigella isolates had high resistance to sulfamethoxazole-trimethoprim (97%), tetracycline (83.6%) ampicillin (58.2%) and chloramphenicol (20.9%). The isolates showed low resistance to nalidixic (4.5%) and ciprofloxacin (3.0%) while there was no resistance to ceftriaxone. The most common multidrug resistance pattern detected in Shigella strains combined sulfamethoxazole-trimethoprim, amoxicillin/ampicillin and tetracyclines.Antibiotic prescriptions were given to 243(85.6%) of the patients presenting with acute bloody diarrhoea. Among these, 94 (38.7%) were given prescriptions for ciprofloxacin, 53 (21.8%) for sulfamethaxazole-trimethiprin and 36(14.8%) for Tetracyclines. Chloramphenicol, amoxicillin/ampicillin, nalidixic acid and ceftriaxone were prescribed to 10.7 %, 3.7%, 2.9% and 0.4% of the patients respectively. A total of 123 (51%) received antibiotics which were ranked to have high resistance (sulfamethoxazole-trimethoprim, tetracyclines ampicillin and chloramphenicol).Conclusion: The high rates of antimicrobial resistance among the commonly prescribed antimicrobials such as sulfamethoxazole-trimethoprim, tetracycline, ampicillin and chloramphenicol is of major concern. Despite recommendations discouraging the empirical use of sulfamethoxazole-trimethoprim, tetracycline, ampicillin and chloramphenicol for treatment of acute bloody diarrhoea, more than half of the patients with acute bloody diarrhoea were still treated with these antibiotics.There is need to train health care workers on the proper management of acute bloody diarrhoea and the importance of adhering to the clinical guidelines

Rolling out Zimbabwean approach to demand-led sanitation in most vulnerable communities

Rural WASH Project (2012-2016) is being implemented in 33 of 60 rural districts in five provinces of Zimbabwe aiming at improving WASH services. One of the major components under this project is the implementation of demand led sanitation and hygiene promotion which focuses on elimination of open defaecation through promotion of household sanitation technologies confirming to national standards. The approach is a hybrid of traditional CLTS, and PHHE and Zimbabwe technology specific sanitation approach. The results from the implementation for the last 23 months suggest a major breakthrough including construction of 57,542 household latrine and 525 ODF communities. It also demonstrated a strong potential of achieving sanitation SDG before 2030 if replicated nationwide with maintaining the current level of efforts. This paper describes the evolution of sanitation approaches in Zimbabwe and share unique experiences from the implementation of the demand led sanitation

Crystal structure and proton conductivity of BaSn0.6Sc0.4O3-delta: insights from neutron powder diffraction and solid-state NMR spectroscopy

The solid-state synthesis and structural characterisation of perovskite BaSn(1–x)Sc(x)O(3–δ) (x = 0.0, 0.1, 0.2, 0.3, 0.4) and its corresponding hydrated ceramics are reported. Powder and neutron X-ray diffractions reveal the presence of cubic perovskites (space group Pm3m) with an increasing cell parameter as a function of scandium concentration along with some indication of phase segregation. (119)Sn and (45)Sc solid-state NMR spectroscopy data highlight the existence of oxygen vacancies in the dry materials, and their filling upon hydrothermal treatment with D(2)O. It also indicates that the Sn(4+) and Sc(3+) local distribution at the B-site of the perovskite is inhomogeneous and suggests that the oxygen vacancies are located in the scandium dopant coordination shell at low concentrations (x ≤ 0.2) and in the tin coordination shell at high concentrations (x ≥ 0.3). (17)O NMR spectra on (17)O enriched BaSn(1–x)Sc(x)O(3–δ) materials show the existence of Sn–O–Sn, Sn–O–Sc and Sc–O–Sc bridging oxygen environments. A further room temperature neutron powder diffraction study on deuterated BaSn(0.6)Sc(0.4)O(3–δ) refines the deuteron position at the 24k crystallographic site (x, y, 0) with x = 0.579(3) and y = 0.217(3) which leads to an O–D bond distance of 0.96(1) Å and suggests tilting of the proton towards the next nearest oxygen. Proton conduction was found to dominate in wet argon below 700 °C with total conductivity values in the range 1.8 × 10(–4) to 1.1 × 10(–3) S cm(–1) between 300 and 600 °C. Electron holes govern the conduction process in dry oxidizing conditions, whilst in wet oxygen they compete with protonic defects leading to a wide mixed conduction region in the 200 to 600 °C temperature region, and a suppression of the conductivity at higher temperature

The Endogenous Th17 Response in NO<inf>2</inf>-Promoted Allergic Airway Disease Is Dispensable for Airway Hyperresponsiveness and Distinct from Th17 Adoptive Transfer

Severe, glucocorticoid-resistant asthma comprises 5-7% of patients with asthma. IL-17 is a biomarker of severe asthma, and the adoptive transfer of Th17 cells in mice is sufficient to induce glucocorticoid-resistant allergic airway disease. Nitrogen dioxide (NO2) is an environmental toxin that correlates with asthma severity, exacerbation, and risk of adverse outcomes. Mice that are allergically sensitized to the antigen ovalbumin by exposure to NO2 exhibit a mixed Th2/Th17 adaptive immune response and eosinophil and neutrophil recruitment to the airway following antigen challenge, a phenotype reminiscent of severe clinical asthma. Because IL-1 receptor (IL-1R) signaling is critical in the generation of the Th17 response in vivo, we hypothesized that the IL-1R/Th17 axis contributes to pulmonary inflammation and airway hyperresponsiveness (AHR) in NO2-promoted allergic airway disease and manifests in glucocorticoid-resistant cytokine production. IL-17A neutralization at the time of antigen challenge or genetic deficiency in IL-1R resulted in decreased neutrophil recruitment to the airway following antigen challenge but did not protect against the development of AHR. Instead, IL-1R-/- mice developed exacerbated AHR compared to WT mice. Lung cells from NO2-allergically inflamed mice that were treated in vitro with dexamethasone (Dex) during antigen restimulation exhibited reduced Th17 cytokine production, whereas Th17 cytokine production by lung cells from recipient mice of in vitro Th17-polarized OTII T-cells was resistant to Dex. These results demonstrate that the IL-1R/Th17 axis does not contribute to AHR development in NO2-promoted allergic airway disease, that Th17 adoptive transfer does not necessarily reflect an endogenously-generated Th17 response, and that functions of Th17 responses are contingent on the experimental conditions in which they are generated. © 2013 Martin et al

Acquisition of naturally occurring antibody responses to recombinant protein domains of Plasmodium falciparum erythrocyte membrane protein 1

Background: Antibodies targeting variant antigens expressed on the surface of Plasmodium falciparum infected erythrocytes have been associated with protection from clinical malaria. The precise target for these antibodies is unknown. The best characterized and most likely target is the erythrocyte surface-expressed variant protein family Plasmodium falciparum erythrocyte membrane protein 1 (PfEMP1). Methods: Using recombinant proteins corresponding to five domains of the expressed A4 var gene, A4 PfEMP1, the naturally occurring antibody response was assessed, by ELISA, to each domain in serum samples obtained from individuals resident in two communities of differing malaria transmission intensity on the Kenyan coast. Using flow cytometry, the correlation in individual responses to each domain with responses to intact A4-infected erythrocytes expressing A4 PfEMP1 on their surface as well as responses to two alternative parasite clones and one clinical isolate was assessed. Results: Marked variability in the prevalence of responses between each domain and between each transmission area was observed, as wasa strong correlation between age and reactivity with some but not all domains. Individual responses to each domain varied strikingly, with some individuals showing reactivity to all domains and others with no reactivity to any, this was apparent at all age groups. Evidence for possible cross-reactivity in responses to the domain DBL4γ was found. Conclusion: Individuals acquire antibodies to surface expressed domains of a highly variant protein. The finding of potential cross-reactivity in responses to one of these domains is an important initial finding in the consideration of potential vaccine targets