Conservation tillage in Kenya : the biophysical processes affecting its effectiveness

Appropriate soil management is important for improved ecosystem functioning and high crop production. This study investigates how different tillage [reduced tillage (RT) and conventional tillage (CT)], crop residue (plus and minus crop residue) and cropping systems (soybean-maize intercropping, rotation and continuous maize) affected (i) soil aggregation, (ii) composition and diversity of microbial populations, (iii) crop residue (CR) disappearance and termite activity, (iv) nitrogen fixation and (v) crop productivity in Kenya. The main experiment in Nyabeda (western Kenya) had been established in 2003, while experiments in Matayos (western Kenya) and Machang’a (eastern Kenya) were established in 2005. Soybean-maize intercropping improved macroaggregation and reduced microaggregates and free silt and clay (P The composition of both bacteria and fungi communities was markedly different in the two tillage systems. With CR application, Simpson’s indices of fungi were in the order intercropping >rotation >continuous maize. In addition, intercropping had highest bacteria diversity indices in the Nyabeda site. CR affected bacteria composition (e.g, in Matayos) and lowered diversity of soil fungi (P CR disappearance was up to 85% of the initial residue in 3.5 months, and the relative contribution of macro- and mesofauna to residue disappearance was 70-95% for surface-placed and 30-70% for buried residues. Soil of termite galleries (mainly sheetings) was more enriched in carbon (1.6%) than bulk farm soil (1.4%) and mound soil (1.2%; P250 Soybean nitrogen derived from the atmosphere (%NDfA) ranged from 42-65%; it was higher (P Seasonal average maize grain yields were 3.2-4.1 t ha-1 in continuous maize, 3.0-3.9 t ha-1 in soybean-maize rotation, and 1.8-2.8 t ha-1 in the soybean-maize intercropping system. Soybean grain yields were 0.92-0.99 t ha-1 in the soybean-maize rotation and 0.52-0.60 t ha-1 in the intercropping system. The net benefits were highest in the soybean-maize intercropping, followed by rotation > continuous maize. Soybean yields were similar between CT and RT; maize yields were lower (P We conclude that (i) despite fast disappearance of CR, its application increases soil aggregation and influences microbial composition and diversity and nitrogen fixation; (ii) for Ferralsols of western Kenya, combining RT and CR is important for improved soil structural stability and, intercropping maize and legume (soybean) leads to better soil structure and also gives higher net benefits than conventional rotation and continuous maize systems; and (iii) RT is appropriate for soybean production; maize yields are lower in RT than in CT due to surface crusing in the RT resulting from inadequate soil cover.Ressourcenschonende Landwirtschaft in Kenia : Die ihre Effektivität beeinflussenden biophysikalischen Prozesse Eine richtige Bodenbearbeitung ist wichtig für die verbesserte Funktion von Ökosystemen und für hohe landwirtschaftliche Erträge. Diese Studie untersucht den Einfluss verschiedener Bodenbearbeitungsmethoden [reduzierte Bodenbearbeitung (reduced tillage; RT) und konventionelle Bodenbearbeitung (conventional tillage; CT)], Ernterückstände (mit und ohne Rückstände) und Anbausysteme (Sojabohnen-Mais Mischkultur, Rotation und fortlaufender Maisanbau) auf (i) Bodenaggregation, (ii) Zusammensetzung und Diversität von Bodenmikrobengemeinschaften, (iii) Verschwinden von Ernterückständen (crop residue; CR) und Aktivität von Termiten, (iv) Stickstofffixierung (N) und (v) landwirtschaftliche Produktivität in Kenia. Die Hauptuntersuchungsfläche in Nyabeda (Westkenia) bestand seit 2003, während die Untersuchungen in Matayos (Westkenia) und Machang’a (Ostkenia) in 2005 begonnen wurden. Mit Sojabohnen-Mais-Zwischenpflanzung verbesserte sich die Makrostruktur des Bodens, während die Mikrostruktur und freier Schluff bzw. Ton (P Die Zusammensetzung sowohl der Bakterien- als auch der Pilzgemeinschaften unterschied sich deutlich in den beiden anderen Systemen. Die Simpson-Indices der Pilze sanken mit Anwendung von Pflanzenrückständen in der Folge Zwischenpflanzung >Rotation >ununterbrochener Maisanbau, und Zwischenpflanzung zeigte die höchsten Bakteriendiversitätindices am Standort in Nyabeda. Pflanzenrückstände beeinflussten die Bakterienzusammensetzung (z.B. in Matayos) und reduzierten die Diversität von Bodenpilzen (P Bis zu 85% der ursprünglichen Pflanzenrückstände verschwand in 3.5 Monaten und der relative Beitrag der Makro-bzw. Mesofauna hierzu war 70-95% für oberflächlich ausgebrachte bzw. 30-70% für eingearbeitete Rückstände. Der Boden der Termitengalerien (hauptsächlich überbaute Laufwege) enthielt mehr Kohlenstoff (1.6%) als Farmboden (1.4%) und Bodenmaterial in Termitenhügeln (1.2%; P250 Sojabohnenstickstoff aus der Atmosphäre (%NDfA) war höher (P-1. Gesamtfixierter Stickstoff bei RT plus CR war mindestens 55% bzw. 34% höher als bei den anderen Bodenbehandlungen (RT minus CR, CT plus CR, bzw. CT minus CR) in den Zwischenpflanzungs- bzw. Rotationssystemen. Die jahreszeitlich abhängigen durchschnittlichen Sojabohnenerträge waren ähnlich bei CT und RT; Maiserträge waren niedriger (P ununterbrochener Maisanbau. Es kann daher davon ausgegangen werden, dass (i) trotz des vollständigen Verschwindens, Pflanzenrückstände die Bodenaggregation erhöhen und die Zusammensetzung und Diversität der Bodenmikroben sowie die Stickstofffixierung beeinflussen; (ii) für die Ferralsols von Westkenia die Kombination von RT und Pflanzenrückständen wichtig ist für eine verbesserte strukturelle Stabilität der Böden, während Zwischenpflanzung von Mais und Hülsenfrüchten (Sojabohnen) zu einer verbesserten Bodenstruktur und auch zu höheren Nettonutzen im Vergleich zur konventionelle Rotation bzw. zu ununterbrochenem Maisanbau führen, und (iii) RT richtig ist für die Sojabohnenproduktion; Maiserträge sind niedriger bei RT als bei CT durch die Oberflächenverkrustung bei RT wegen der unzureichenden Bodenbedeckung

Micronutrient deficiencies in African soils and the human nutritional nexus: opportunities with staple crops

A synthesis of available agronomic datasets and peer-reviewed scientific literature was conducted to: (1) assess the status of micronutrients in sub-Saharan Africa (SSA) arable soils, (2) improve the understanding of the relations between soil quality/management and crop nutritional quality and (3) evaluate the potential profitability of application of secondary and micronutrients to key food crops in SSA, namely maize (Zea mays L.), beans (Phaseolus spp. and Vicia faba L.), wheat (Triticum aestivum L.) and rice (Oryza sativa L.). We found that there is evidence of widespread but varying micronutrient deficiencies in SSA arable soils and that simultaneous deficiencies of multiple elements (co-occurrence) are prevalent. Zinc (Zn) predominates the list of micronutrients that are deficient in SSA arable soils. Boron (B), iron (Fe), molybdenum (Mo) and copper (Cu) deficiencies are also common. Micronutrient fertilization/agronomic biofortification increases micronutrient concentrations in edible plant organs, and it was profitable to apply fertilizers containing micronutrient elements in 60–80% of the cases. However, both the plant nutritional quality and profit had large variations. Possible causes of this variation may be differences in crop species and cultivars, fertilizer type and application methods, climate and initial soil conditions, and soil chemistry effects on nutrient availability for crop uptake. Therefore, micronutrient use efficiency can be improved by adapting the rates and types of fertilizers to site-specific soil and management conditions. To make region-wide nutritional changes using agronomic biofortification, major policy interventions are needed

Soil health and ecosystem services: Lessons from sub-Sahara Africa (SSA)

Management practices to improve soil health influence several ecosystem services including regulation of water flows, changes in soil biodiversity and greenhouse gases that are important at local, regional and global levels. Unfortunately, the primary focus in soil health management over the years has been increasing crop productivity and to some extent the associated economics and use efficiencies of inputs. There are now efforts to study the inter-relationship of associated ecosystem effects of soil health management considering that sustainable intensification cannot occur without conscious recognition of these associated non-provisioning ecosystem services. This review documents the current knowledge of ecosystem services for key management practices based on experiences from agricultural lands in sub-Sahara Africa (SSA). Here, practicing conservation agriculture (CA) and Integrated Soil fertility management (ISFM) have overall positive benefits on increasing infiltration (> 44), reducing runoff (> 30%) and soil erosion (> 33%) and increases soil biodiversity. While ISFM and Agroforestry increase provisioning of fuelwood, fodder and food, the effect of CA on the provisioning of food is unclear. Also, considering long-term perspectives, none of the studied soil health promoting practices are increasing soil organic carbon (SOC). Annual contributions to greenhouse gases are generally low (< 3 kg N2O ha−1) with few exceptions. Nitrogen leaching vary widely, from 0.2 to over 200 kg N ha−1 and are sometimes inconsistent with N inputs. This summary of key considerations for evaluating practices from multiple perspectives including provisioning, regulating, supporting and cultural ecosystem services is important to inform future soil health policy and research initiatives in SSA

Soil fertility management in Babati: A practical guide on good agricultural management practices in smallholder farming systems

Working with farmers and extension staff within the Ministry of Agriculture and interactions with broad range of researchers across national research and CGIAR Centers operating in Northern Tanzania resulted in a wealth of experience and knowledge that we bring forward in this guide. We have observed wide yield gaps across farms and experienced first-hand key challenges faced by farmers as we worked in their fields, interacted in field days, participatory technology evaluations, exchange visits and brainstorming meetings with farmers. High attainable yields observed by some individual farmers and researchers in experimental and demonstration trials clearly demonstrate potential of applying simple agronomic and other supporting practices to change fortunes of farmers. This is what inspired this guide. Although expressed through simple illustrations and language, most of the data and information are generated through rigorous scientific and data analysis approaches to ensure accuracy of the information. The guide, a knowledge intensive resource, brings together key messages from 6 years of International Center for Tropical Agriculture’s (CIAT) operations in Babati and is a valuable management tool for farmers. It is also an essential reference tool for local agricultural extension and other stakeholders involved in the field of agriculture. The agricultural extension staff reviewed this guide during a workshop held on 17 June 2019 in Babati. These staff included: Jetrida Kyekaka, the District Agriculture, Irrigation and Cooperative Officer (DAICO); Rose Pallangjo, Jonus Masamu and Paulo Tarmo, the District Extension Officers; and Adelta Macha, an extension officer in Gallapo village

Improved agronomy increases wheat yield In Africa RISING action sites

United States Agency for International Developmen

Landscape natural resources management with soil and water conservation practices

United States Agency for International Developmen

Microbes matter: Unravelling trade-offs between integrated management options and microbial functions

We start with key highlights. We then present the soils as influenced by management practices followed by influences to overall microbes. Effects on specific functional groups including zinc and phosphorus solubilization follows before a presentation of how these relate with the soil properties. This is followed by a section on enzyme activities and another on specific functional genes and fungal to bacterial ratio. We then present data on CO2 evolution and mineralization of nitrogen and phosphorus. We finish with application of micro-biology through bio-inoculants and then a summary of research gaps