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Iron and zinc are essential micronutrients for human health often found in insufficient quantities in the diet. Biofortification of seed crops has been undertaken to reduce micronutrient malnutrition. The objectives of this study were to identify variability for seed Fe, Zn, P, and phytic acid levels in an [F.sub.5:7] recombinant inbred line (RIL) population developed from a cross between AND696 and G19833, both common beans (Phaseolus vulgaris L.) of Andean origin. Quantitative trait loci (QTL) analysis was conducted with data from 2 yr and 2 P treatments with a previously described linkage map of AND696/ G19833. Significant environmental and genetic variability for Fe, Zn, and P levels was identified, and Fe and Zn levels were correlated (up to r = 0.53). Quantitative trait loci for seed Fe and Zn co-localized on three linkage groups (B1, B6, and B11). On B6, a QTL for Fe ([R.sup.2] = 0.36) was found at the same marker interval as a QTL for seed Zn ([R.sup.2] = 0.39), both derived from AND696. Quantitative trait loci for seed P were identified on six linkage groups and explained 17 to 55% of the total phenotypic variation depending on year and environment.

Tolerance to low P soils is a desirable trait in common bean (Phaseolus vulgaris L.) cultivars grown in acid-weathered soils. Genetic variability in response to P-deficient soils exists in the Andean gene pool. G19833, a low P-tolerant indeterminate Andean landrace, has been evaluated for quantitative trait loci (QTL) and tolerance to low P in combination with Mesoamerican parents. Our goal was to expand our understanding of phenotypic traits and QTL from G19833 expressed in an Andean background. An [F.sub.5:7] recombinant inbred line (RIL) population developed from two Andean bean genotypes, G19833 and AND696, a determinate line susceptible to low P soils, was examined under low and high soil P levels in replicated field trials. Phosphorus uptake was reduced by 70% and yield by 60% in low P compared to high P treatments. A linkage map was developed with 11 linkage groups and a total length of 1105 cM. Quantitative trait loci for root growth, seed yield, seed P content, and P use efficiency colocalized near the fin gene on linkage group B1. Quantitative trait loci for root growth traits, seed yield, and P uptake colocalized on B11. Quantitative trait loci for root length density (cm [cm.sup.-3]) and root surface area ([cm.sup.2]) did not colocalize with QTL for P uptake. This study indicates that root traits did not play an important role in tolerance to low P soil in an Andean x Andean cross, contrary to previous results with the same P-efficient Andean parent (G19833) crossed to a Mesoamerican bean genotype.

A potato (Solanum tuberosum L.) experiment from 2002 to 2004 examined fallow or winter rye (Secale cereale L.) (average residues ~1 Mg [ha.sup.-1]) cover crop systems with a split-plot design of 0 or 5.6 Mg [ha.sup.-1] poultry manure. A 75-L container experiment used field trial soil to evaluate N dynamics in the presence and absence of N fertilizer. Organic N source (manure, cover crop residues, or both) availability was used to adjust fertilizer rate downward to provide an estimated 224 kg N [ha.sup.-1] for all treatments. Plant growth, N uptake, and tuber yield were monitored, along with soil organic N status and light-fraction organic matter. In the field, the integrated treatment (179 kg N [ha.sup.-1] fertilizer + manure) consistently increased tuber yield and N uptake efficiency by 20% compared with the unamended conventional management (224 kg N [ha.sup.-1] fertilizer). Similarly, tuber yield and N uptake in the integrated treatments of the container experiment were 14 to 33% higher than the fertilized, unamended treatment. In the absence of fertilizer, rye cover crop and manure enhanced tuber yield 40 to 210% compared with unamended plants. The release of N from diverse sources was in apparent synchrony with plant demand, as indicated by monitoring of N[O.sub.3]-N dynamics and the presence of light-fraction N. Although manure application was associated with higher N input, subsoil N[O.sub.3]-N in manured and unmanured treatments averaged 6.7 and 7.9 mg [kg.sup.-1], respectively. High productivity and N efficiency were associated with integrating organic and inorganic N sources, which represents an environmentally and agronomically sound management strategy. Abbreviations: LFOM, light-fraction organic matter; NMP nitrogen mineralization potential.

Effective extension systems are vital to smallholder agriculture. Education on sustainable management involves complex interactions and communication flows among information providers and practitioners. Farmer practice is often overlooked within extension knowledge systems, resulting in incompatible recommendations and barriers to sustainable agriculture. This study investigates the diversity of smallholder agricultural practices, with a focus on maize-legume systems in Tanzania, including seasonal cropping patterns and management, as well as linkages to extension recommendations and information flows. We used a mixed methods approach to assess the state of extension and farmer practice around maize-legume production in Tanzania. Household and plot-level survey data (n = 220) and focus group discussions (n = 5) and extension information was ascertained through interviews with key stakeholders (n = 12) and a survey of village-based extension advisors (n = 193). We found legume management practices were highly local. In the Southern Highlands for example, farmers produced from one to three bean crops per year, using a range of planting arrangements. Further, extension recommendations often did not take into account the varieties, fertilizer or plant spacing used by farmers. This comprehensive study of extension knowledge systems in Tanzania highlights the persistent disconnects that occur at multiple levels, acting as a barrier to sustainable intensification of smallholder farming. [ABSTRACT FROM AUTHOR]

Remobilization of P from vegetative tissues can be an important source of grain P in common bean (Phaseolus vulgaris L.). Yet, data on the extent of remobilization of P from roots is scarce. We measured P remobilization from roots and leaves and examined the influence of P nutrition on remobilization patterns and tissue longevity. A split-root system was used to expose a portion of the root system (compartment roots) to low-P treatments independently from those imposed on the main root system. Phosphorus content of retained leaves, abscised leaves, stems, pods, seeds, and roots were observed over time. Leaf remobilization supplied over half of the pod plus seed P. Flux analysis suggested that leaf remobilization occurred earlier in low-P than it did in high-P plants. Root P content of compartment roots did not decrease with ontogeny. We compared remobilization patterns of root P in low-P and high-P plants in a short-term experiment using 32P applied to roots grown in either low-P or high-P compartments. Compartment roots retained over 80% of absorbed 32P almost all cases. The exception was roots of high-P plants grown in a high-P compartment, which retained only 20% of absorbed 32P. Together these results indicate common bean roots retain P when soil P levels are low. This behavior is in contrast to that of leaves and stems which remobilize P to the grain at both low and high levels of soil P fertility.

This paper explores the role of women empowerment and labour on enabling farmers to cross two hurdles: adopt and intensify soil fertility management (SFM), coming after six decades of SFM research that disseminated several technologies. Despite the assertion that productivity gains cannot be realized unless drivers of soil degradation are addressed, SFM usage is low. We collected data from a systematically drawn random sample of 238 farmers, representing 30% of farming households in five villages in Malawi's Rift Valley escarpments and analysed using a double‐hurdle model. Descriptive results show that 90% of the respondents used inorganic fertilizers, 72% planted legumes and 57% applied organic manure. The empirical analysis shows that one percentage point increase in dependency ratio reduces probability to apply organic amendments by 0.4 percentage points and erodes the positive influence of increasing labour on application of inorganic fertilizer. As women become increasingly empowered in decision‐making, there are significant trade‐offs: a percentage point increase in women empowerment in agriculture index (WEAI) potentially leads to a one‐third percentage point increase in the area allocated to legumes but reduces the amount of organic manure applied with higher elasticity of two percentage points. Considering the trade‐offs, sustainable intensification could be achieved by harnessing the positive influences while concurrently reducing the negative ones over a decision space. Notably, addressing the negative effect associated with women empowerment on manuring could unlock potentials for integrated SFM as women are already engaged in legume cropping. [ABSTRACT FROM AUTHOR]