Resource concentration dilutes a key pest in indigenous potato agriculture

Modern restructuring of agricultural landscapes, due to the expansion of monocultures and the resulting elimination of non-crop habitat, is routinely blamed for rising populations of agricultural insect pests. However, landscape studies demonstrating a positive correlation between pest densities and the spatial extent of crop monocultures are rare. We test this hypothesis with a data set from 140 subsistence farms in the Andes and find the inverse correlation. Infestations by the Andean potato weevil (Premnotrypes spp.), the most important pest in Andean potato agriculture, decrease with increasing amounts of potato in the landscape. A statistical model predicts that aggregating potato fields may outperform the management of Andean potato weevils by IPM and chemical control. We speculate that the strong pest suppression generated by aggregating potato fields may partly explain why indigenous potato farmers cluster their potato fields under a traditional rotation system common in Andean agriculture (i.e., “sectoral fallow”). Our results suggest that some agricultural pests may also respond negatively to the expansion of monocultures, and that manipulating the spatial arrangement of host crops may offer an important tool for some IPM programs

Unearthing unevenness of potato seed networks in the high Andes: a comparison of distinct cultivar groups and farmer types following seasons with and without acute stress

The purpose of the research was to understand the fine-grained dynamics underlying potato seed networks in a center of crop origin and biodiversity, the central Andes of Peru, by differentiating between seasons with and without acute stress (i.e. frost, late blight), cultivar groups, and farmer types. Cultivar groups were classified into (i) bred varieties, (ii) commercial floury landraces, (iii) non-commercial floury landraces (single cultivars), (iv) non-commercial floury landraces (mixed cultivars), and (v) bitter landraces. Farmer types were classified as (i) general farmers, (ii) seed specialists, and (iii) custodian farmers. We documented seed provisions and acquisitions through the application of a semi-structured survey to 336 households in 2014-2015 in two main regions of the Peruvian central Andes: Huancavelica and Pasco-Junin. Farmers self-determined the most recent seasons with and without acute stress, specified the cause of the stress (i.e. frost, hail, late blight, drought), and described seed transactions for each season. The survey consisted of ten sections: (i) socioeconomic data; (ii) cropping season; iii) cultivar-level procurement; iv) seed volumes; v) specific seed sources and sinks; vi) social relationship to providers and clients; vii) seed transaction types; viii) place (s) of seed transaction; ix) seed destination/origin; x) quality guarantee of seed (including certification). For each respondent, every single transaction of seed acquisition and provision was recorded as a separate entry. Results confirm that seed networks are uneven and distinct for cultivar groups and farmer types. The study details the adaptations the system makes in the aftermath of acute stress and assesses the implications of its dynamics for conservation. Seed networks did re-organize following seasons with acute seed stress. A notable shift involved a contraction of seed networks within sub-regional clusters. Following stress, the directionality of seed provision versus acquisition inverts. We conclude that the self-regulatory capacity of farmer seed networks represents a strong safety net through which smallholders can respond to crop failure and seed stress. (2014-10

The spatial-temporal dynamics of potato agrobiodiversity in the highlands of central Peru: a case study of smallholder management across farming landscapes.

In the high Andes, environmental and socio-economic drivers are transforming agriculture and presumably affecting the in situ conservation of potato (Solanum spp.). To monitor the use and conservation of intraspecific diversity, systematic and comparative studies across agricultural land-use systems are needed. We investigated the spatial-temporal dynamics of potato in two landscapes of Peru’s central Andes: A highland plateau (Huancavelica) compared to an eastern slope (Pasco). We examined household-level areal allocations, altitudinal distribution, sectoral fallowing practices, and the conservation status for three main cultivar groups: (i) Bred varieties, (ii) floury landraces, and (iii) bitter landraces. Mixed methods were used to survey 323 households and the 1101 potato fields they managed in 2012–2013. We compared the contemporary altitudinal distribution of landraces with 1975–1985 altimeter data from the International Potato Center. Intensification is occurring in each landscape while maintaining high intraspecific diversity. Access to land and production for sale compared to consumption significantly affected smallholder management and differentiated landscapes. Most landraces were scarce across households: 45.4% in Huancavelica and 61.7% in Pasco. Potato cultivation has moved upward by an average of 306 m since 1975. Landrace diversity is versatile but unevenly distributed across landscapes. This requires adaptive ways to incentivize in situ conservation

Iron concentration of potato and sweetpotato clones as affected by location

The effect of growing location on the iron concentration of potato and sweetpotato as determined by ICP-MS was evaluated using freeze dried and milled samples from peeled raw potato tubers and sweetpotato roots. Significant variation of the iron concentrations due to genotype (clone or variety), location and genotype × location interaction was found for potato and sweetpotato. However, for potato, the iron concentration levels were mostly attributed to genotype which account for 62.89% of the total variance whereas for sweetpotato the iron concentration levels were mostly attributed to location which account for 76.16% of the total variance. Acidic soils seem to favor the iron absorption by the potato and sweetpotato plant while alkaline soils seem to diminish iron absorption. The mean iron concentration of the potato clones and varieties was higher in Yanamachay and Paltamachay, localities with acidic soils and high organic matter content; and was lower in Tacsana, the locality with the highest pH in the soil, lowest percentage of organic matter and highest proportion of sand. The mean iron concentration of the sweetpotato clones was drastically lower in Huaral, the locality with alkaline soil, than in San Ramon and Pucallpa. A broader and deeper designed study is planned to confirm the results found in this preliminary study