KUTUN : a morphogenetic model for cotton (Gossypium hirsitum L.)

A whole crop model for growth and development of cotton ( Gossypium hirsutum L.) is presented. The model is based on previous extensive studies on plant morphogenesis, growth of fruits and canopy photosynthesis. The crop model basically is a carbohydrate budget, but all processes are regulated by an underlying morphogenetic template, derived from the previous studies on plant morphogenesis. A cotton crop is considered as a set of partly autonomous, interacting strata, each consisting of a mainstem leaf and the adjoining sympodial branch, with their associated stem (and root) tissue. Growth of fruits and maintenance respiration have absolute priority for the allocation of assimilates but vegetative growth and growth of squares in any stratum depend to a large extent on the assimilates produced in that stratum. This stratification concept, together with the potential growth rates of all tissues in dependence of their developmental age and assimilate production, calculated for each stratum separately are the core of the simulation procedures. The crop model is shown to accurately generate a large number of well-documented semi-quantitive growth phenomena of cotton. Some lines for further research and development of the model are indicated

Looking back and moving forward: 50 years of soil and soil fertility management research in sub-Saharan Africa

Article purchased; Published online: 02 Nov 2017Low and declining soil fertility has been recognized for a long time as a major impediment to intensifying agriculture in sub-Saharan Africa (SSA). Consequently, from the inception of international agricultural research, centres operating in SSA have had a research programme focusing on soil and soil fertility management, including the International Institute of Tropical Agriculture (IITA). The scope, content, and approaches of soil and soil fertility management research have changed over the past decades in response to lessons learnt and internal and external drivers and this paper uses IITA as a case study to document and analyse the consequences of strategic decisions taken on technology development, validation, and ultimately uptake by smallholder farmers in SSA. After an initial section describing the external environment within which soil and soil fertility management research is operating, various dimensions of this research area are covered: (i) ‘strategic research’, ‘Research for Development’, partnerships, and balancing acts, (ii) changing role of characterization due to the expansion in geographical scope and shift from soils to farms and livelihoods, (iii) technology development: changes in vision, content, and scale of intervention, (iv) technology validation and delivery to farming communities, and (v) impact and feedback to the technology development and validation process. Each of the above sections follows a chronological approach, covering the last five decades (from the late 1960s till today). The paper ends with a number of lessons learnt which could be considered for future initiatives aiming at developing and delivering improved soil and soil fertility management practices to smallholder farming communities in SSA

Mixed cropping experiments with maize and groundnuts

Experiments were carried out during 3 seasons in the Yaounde area, Cameroon, in order to evaluate maize/groundnut mixtures compared with pure stands. Both crops had similar growth duration. Total grain/seed yields of both crops combined were lower for mixtures than for pure maize, but mixtures were found to be advantageous over pure stands in terms of relative yield total (RYT): in the Sept.-Dec. season of 1975 an av. of 6% more area would have been needed in pure stands to attain the same yield of each sp. as in the mixtures. In the March-July season of 1976 this was 16%. The results are discussed in terms of limiting factors. Results of a 3rd experiment suggest that the mixtures reduce the risk of supra-opt. population density compared with pure maize under severely limiting N availability. (Abstract retrieved from CAB Abstracts by CABI’s permission

An agricultural analysis of rainfall reliability for Cameroon

An improvement of Manning's analysis of rainfall reliability is presented. Confidence limits of 20-day rainfall totals are calculated with a simple normalizing transformation. Rainfall distribution within a 20-day period is assessed by simply counting the frequency of occurrence of dry spells exceeding 10 days duration. The joint probability of deficient 20-day rainfall total and dry spell occurrence is estimated. The analysis is applied to two practical examples in Cameroon, including the semi-arid northern area. ADDITIONAL ABSTRACT: An improvement of Manning's analysis of rainfall reliability is presented. Confidence limits of 20-day rainfall totals were calculated with a simple normalizing transformation. Rainfall distribution within a 20-day period was assessed by simply counting the frequency of occurrence of dry spells exceeding 10 days duration. The joint probability of deficient 20-day rainfall total and dry spell occurrence was estimated. The analysis was applied to 2 practical examples in Cameroon. (Abstract retrieved from CAB Abstracts by CABI’s permission

Farmers maize yields in S.W. Nigeria and the effect of variety and fertilizer: an analysis of variability in onfarm trials

Farmer-managed trials in developing countries often show great variability in yield and treatment effects. The use of statistical techniques is demonstrated to explain this variability in a maize + cassava intercropping trial in southwestern Nigeria. Concomitant variables, measured in the trial fields, are used as covariates in the ANOVA and as regressors in the analysis of mean site yield. It was found that a new maize variety (TZSR-W) performed better than the lcoal irrespective of farmers' yield level. Fertilizer effect increased as farmers' overall yield level (reflected in their mean site yield) increased. At current fertilizer and maize prices, fertilizer was profitable for all except the poorest-yielding fields. Variation in yield level was partly explained by degree of shade and stand losses during the season. Part of the stand losses was due to termites. The majority of female farmers in the sample had lower yields than males because of a combination of factors such as shade, late planting, poor weeding and longer occupation of the land