The Zambia Children\u27s KS-HHV8 Study: Rationale, Study Design, and Study Methods

The epidemic of human immunodeficiency virus in Zambia has led to a dramatic rise in the incidence of human herpesvirus-8 (HHV-8)–associated Kaposi\u27s sarcoma in both adults and children. However, there is a paucity of knowledge about the routes of HHV-8 transmission to young children. The Zambia Children\u27s KS-HHV8 Study, a large, prospective cohort study in Lusaka, Zambia, was launched in 2004 to investigate the role of household members as a source of HHV-8 infection in young children and social behaviors that may modify the risk of HHV-8 acquisition. This cohort is distinct from other epidemiologic studies designed to investigate HHV-8 incidence and transmission because it recruited and followed complete households in the urban central African context. Between July 2004 and March 2007, 1,600 households were screened; 368 households comprising 464 children and 1,335 caregivers and household members were enrolled. Follow-up of this population continued for 48 months postrecruitment, affording a unique opportunity to study horizontal transmission of HHV-8 and understand the routes and sources of transmission to young children in Zambia. The authors describe the study rationale, design, execution, and characteristics of this cohort, which provides critical data on the epidemiology and transmission of HHV-8 to young children in Zambia

Data from: Maize-nutrient response functions for Eastern and Southern Africa

Information is scarce for maize (Zea mays L.) response to nutrient application for many production areas in tropical Africa. Research was conducted to determine macronutrient response functions and to diagnose Mg–S–Zn–B deficiencies. Site–year × N-rate interactions within countries often accounted for little variation in yield relative to the N-rate effect. Country mean grain yield responses to N-rate were curvilinear to plateau, but linear in Malawi. Although mean yields differed, the response to N was similar for Kenya, Tanzania, and Zambia with a mean yield increase of 0.94 Mg ha–1 due to 50 kg ha–1 N compared with 1.59 Mg ha–1 for Malawi and Rwanda. Response to N was related to yield with no fertilizer applied (r = 0.40). Only Rwanda had mean responses to P and K with respective yield increases of 0.99 and 0.22 Mg ha–1 due to 15 kg ha–1. Application of Mg–S–Zn–B caused a mean yield increase of 0.73 Mg ha–1 in Rwanda but had no effect in other countries. Application of affordable fertilizer to twice as much land at 50% compared with 100% of the economically optimum rate results in mean gains of 50% for production and agronomic efficiency and 72% for profit/cost ratio. Soil test results were not related to response to applied nutrients but historical yield appears to be weakly predictive of N response. The determined country-level P and K response functions can be widely applied, except for Kenya, in consideration of other available information. The response to Mg–S–Zn–B in Rwanda needs further investigation

ESA Maize Fertilizer Response Data

This data was generated from collaborative research in five countries of eastern and southern Africa using a similar treatment structure for determination of maize response functions to fertiizer N, P, and K and for the diagnosis of deficiencies for Mg, S, Zn and B

Maize-nutrient response functions for eastern and southern Africa

Information is scarce for maize (Zea mays L.) response to nutrient application for many production areas in tropical Africa. Research was conducted to determine macronutrient response functions and to diagnose Mg–S–Zn–B deficiencies. Site–year × N-rate interactions within countries often accounted for little variation in yield relative to the N-rate effect. Country mean grain yield responses to N-rate were curvilinear to plateau, but linear in Malawi. Although mean yields differed, the response to N was similar for Kenya, Tanzania, and Zambia with a mean yield increase of 0.94 Mg ha–1 due to 50 kg ha–1 N compared with 1.59 Mg ha–1 for Malawi and Rwanda. Response to N was related to yield with no fertilizer applied (r = 0.40). Only Rwanda had mean responses to P and K with respective yield increases of 0.99 and 0.22 Mg ha–1 due to 15 kg ha–1. Application of Mg–S–Zn–B caused a mean yield increase of 0.73 Mg ha–1 in Rwanda but had no effect in other countries. Application of affordable fertilizer to twice as much land at 50% compared with 100% of the economically optimum rate results in mean gains of 50% for production and agronomic efficiency and 72% for profit/cost ratio. Soil test results were not related to response to applied nutrients but historical yield appears to be weakly predictive of N response. The determined country-level P and K response functions can be widely applied, except for Kenya, in consideration of other available information. The response to Mg–S–Zn–B in Rwanda needs further investigation

Data from: Diagnosis of crop secondary and micro-nutrient deficiencies in sub-Saharan Africa

Crop production in sub-Saharan Africa has numerous biotic and abiotic constraints, including nutrient deficiencies. Information on crop response to macronutrients is relatively abundant compared with secondary and micronutrients (SMN). Data from 1339 trial replicates of 280 field trials conducted from 2013 to 2016 in 11 countries were analyzed for the diagnosis of SMN deficiencies. The diagnostic data included relative yield response (RYR) and soil and foliar test results. The RYR to application of a combination of Mg, S, Zn, and B (Mg-S-Zn-B) relative to a comparable N-P-K treatment was a >5% increase for 35% of the legume blocks and 60% of the non-legume blocks. The frequencies of soil test Zn, Cu, and B being below their critical level were 28, 2 and 10% for eastern and southern Africa, respectively, and 55, 58 and 89% for western Africa, while low levels for other SMN were less frequent. The frequency of foliar results indicating low availability were 58% for Zn, 16% for S and less for other SMN. The r2 values for relationships between soil test, foliar test and RYR results were <0.035 with little complementarity except for soil test Zn and B with cassava (Manihot esculenta L. Crantz) RYR in Ghana, and foliar Zn with cereal RYR in Uganda. Positive RYR is powerful diagnostic information and indicative of good profit potential for well-targeted and well-specified SMN application. Geo-referenced RYR, soil analysis and foliar analysis results for diagnosis of SMN deficiencies in 11 countries of sub-Saharan Africa were generally not complementary

Data from: Maize-nutrient response information applied across Sub-Saharan Africa

The profit potential for a given investment in fertilizer use can be estimated using representative crop nutrient response functions. Where response data is scarce, determination of representative response functions can be strengthened by using results from homologous crop growing conditions. Maize (Zea mays L.) nutrient response functions were selected from the Optimization of Fertilizer Recommendations in Africa (OFRA) database of 5500 georeferenced response functions determined from field research conducted in Sub-Saharan Africa. Three methods for defining inference domains for selection of response functions were compared. Use of the OFRA Inference Tool (OFRA-IT; http://agronomy.unl.edu/OFRA) resulted in greater specificity of maize N, P, and K response functions with higher R2 values indicating superiority compared with using the Harvest Choice Agroecological Zones (HC-AEZ) and the recommendation domains of the Global Yield Gap Atlas project (GYGA-RD). The OFRA-IT queries three soil properties in addition to climate-related properties while the latter two options use climate properties only. The OFRA-IT was generally insensitive to changes in criteria ranges of 20–25% used in queries suggesting value in using wider criteria ranges compared with the default for information scarce crop nutrient response functions

Tropical Africa Crop Nutrient Diagnosis data set Jan 2019

The data are from 1339 trial replicates of 280 field trials conducted from 2013 to 2016 in 11 countries of tropical Africa. The data were analyzed for the diagnosis of secondary and micronutrient deficiencies. The diagnostic data included relative yield response to application of a combination of Mg, S, Zn, and B (Mg-S-Zn-B) relative to a comparable N-P-K treatment. Soil and foliar sample data is also included. The data is in an Excel file with seven worksheets plus a ReadMe worksheet