Hemp (Cannabis sativa L.) leaf photosynthesis in relation to nitrogen content and temperature: implications for hemp as a bio-economically sustainable crop

Hemp (Cannabis sativa L.) may be a suitable crop for the bio-economy as it requires low inputs while producing a high and valuable biomass yield. With the aim of understanding the physiological basis of hemp's high resource-use efficiency and yield potential, photosynthesis was analysed on leaves exposed to a range of nitrogen and temperature levels. Light-saturated net photosynthesis rate (Amax) increased with an increase in leaf nitrogen up to 31.2\uc2 \uc2\ub1\uc2 1.9\uc2 \uce\ubcmol m\ue2\u88\u922 s\ue2\u88\u921 at 25\uc2 \uc2\ub0C. The Amax initially increased with an increase in leaf temperature (TL), levelled off at 25\ue2\u80\u9335\uc2 \uc2\ub0C and decreased when TL became higher than 35\uc2 \uc2\ub0C. Based on a C3 leaf photosynthesis model, we estimated mesophyll conductance (gm), efficiency of converting incident irradiance into linear electron transport under limiting light (\uce\uba2LL), linear electron transport capacity (Jmax), Rubisco carboxylation capacity (Vcmax), triose phosphate utilization capacity (Tp) and day respiration (Rd), using data obtained from gas exchange and chlorophyll fluorescence measurements at different leaf positions and various levels of incident irradiance, CO2 and O2. The effects of leaf nitrogen and temperature on photosynthesis parameters were consistent at different leaf positions and among different growth environments except for \uce\uba2LL, which was higher for plants grown in the glasshouse than for those grown outdoors. Model analysis showed that compared with cotton and kenaf, hemp has higher photosynthetic capacity when leaf nitrogen is <2.0\uc2 g N m\ue2\u88\u922. The high photosynthetic capacity measured in this study, especially at low nitrogen level, provides additional evidence that hemp can be grown as a sustainable bioenergy crop over a wide range of climatic and agronomic conditions

The role of Amazonian anthropogenic soils in shifting cultivation: Learning from farmers’ rationales

We evaluated farmers’ rationales to understand their decision making in relation to the use of fertile anthropogenic soils, i.e., Amazonian dark earths (ADE), and for dealing with changes in shifting cultivation in Central Amazonia. We analyzed qualitative information from 196 interviews with farmers in 21 riverine villages along the Madeira River. In order to decide about crop management options to attain their livelihood objectives, farmers rely on an integrated and dynamic understanding of their biophysical and social environment. Farmers associate fallow development with higher crop yields and lower weed pressure, but ADE is always associated with high yields and high weeding requirements. Amazonian dark earths are also seen as an opportunity to grow different crops and/or grow crops in more intensified management systems. However, farmers often maintain simultaneously intensive swiddens on ADE and extensive swiddens on nonanthropogenic soils. Farmers acknowledge numerous changes in their socioeconomic environment that affect their shifting cultivation systems, particularly their growing interaction with market economies and the incorporation of modern agricultural practices. Farmers considered that shifting cultivation systems on ADE tend to be more prone to changes leading to intensification, and we identified cases, e.g., swiddens used for watermelon cultivation, in which market demand led to overintensification and resulted in ADE degradation. This shows that increasing intensification can be a potential threat to ADE and can undermine the importance of these soils for agricultural production, for the conservation of agrobiodiversity, and for local livelihoods. Given that farmers have an integrated knowledge of their context and respond to socioeconomic and agro-ecological changes in their environment, we argue that understanding farmers’ knowledge and rationales is crucial to identify sustainable pathways for the future of ADE and of smallholder agriculture in Amazonia. © 2016 by the author(s)

Vegetable seed systems among ethnic minority communities in northern Vietnam

Despite the potential of vegetables for nutrition and income in Northern Vietnam, inadequate access to quality seed is a major constraint affecting production, diversity and diet quality. Both self-saved seed and bought seed are important sources for farmers and are linked to the primary purpose of production, market access, seed production knowledge and skills, and trustworthiness of the source. Vegetable diversity, seasonal availability and seed access varies with ethnic group, location, type of and specific vegetables requiring contextualisation of nutrition-sensitive interventions. There are opportunities for farmer sharing and exchange of seeds, vegetables, and knowledge, for safeguarding diversity, promote dietary quality, and improve farmer income

French bean seed production calendar

French bean seed production calendars for awareness creation and capacity building activities in vegetable and seed production and storage among ethnic minority vegetable farming households in Northern Vietnam. Particularly designed with and for the H’Mong and Dao people in Lao Cai province and Thai people in Son La province in English and Vietnamese

H'mong mustard seed production calendar

H’mong mustard seed production calendars for awareness creation and capacity building activities in vegetable and seed production and storage among ethnic minority vegetable farming households in Northern Vietnam. Particularly designed with and for the H’Mong and Dao people in Lao Cai province and Thai people in Son La province in English and Vietnamese

Vegetable seed systems for ethnic minorities in northern Vietnam for enhanced nutrition and income

Vegetables are a main source of nutrition and income for ethnic minority farmers in Vietnam’s Northern highlands. While the consumption of vegetables and value chains for fresh retail produce and seed markets offer huge opportunities for household nutrition security and development, and particularly women inclusion, current smallholder systems suffer from multiple problems. The Integrated vegetable seed systems development project addressed these issues by elucidating how, and under what conditions, increased access and use of high-quality seed translates into enhanced smallholder nutrition and income security. This poster provides the project highlights presented at the NL-CGIAR Conference, 2-3 November 2022

Using chromosome introgression lines to map quantitative trait loci for photosynthesis parameters in rice (Oryza sativa L.) leaves under drought and well-watered field conditions

Photosynthesis is fundamental to biomass production, but sensitive to drought. To understand the genetics of leaf photosynthesis, especially under drought, upland rice cv. Haogelao, lowland rice cv. Shennong265, and 94 of their introgression lines (ILs) were studied at flowering and grain filling under drought and well-watered field conditions. Gas exchange and chlorophyll fluorescence measurements were conducted to evaluate eight photosynthetic traits. Since these traits are very sensitive to fluctuations in microclimate during measurements under field conditions, observations were adjusted for microclimatic differences through both a statistical covariant model and a physiological approach. Both approaches identified leaf-to-air vapour pressure difference as the variable influencing the traits most. Using the simple sequence repeat (SSR) linkage map for the IL population, 1–3 quantitative trait loci (QTLs) were detected per trait–stage–treatment combination, which explained between 7.0% and 30.4% of the phenotypic variance of each trait. The clustered QTLs near marker RM410 (the interval from 57.3 cM to 68.4 cM on chromosome 9) were consistent over both development stages and both drought and well-watered conditions. This QTL consistency was verified by a greenhouse experiment under a controlled environment. The alleles from the upland rice at this interval had positive effects on net photosynthetic rate, stomatal conductance, transpiration rate, quantum yield of photosystem II (PSII), and the maximum efficiency of light-adapted open PSII. However, the allele of another main QTL from upland rice was associated with increased drought sensitivity of photosynthesis. These results could potentially be used in breeding programmes through marker-assisted selection to improve drought tolerance and photosynthesis simultaneously

Robust increases of land equivalent ratio with temporal niche differentiation : A meta-quantile regression

Intercropping has been shown to be land use efficient, but there is a large variation in the land equivalent ratio (LER) among studies. We used quantile regression to estimate the effect of temporal niche differentiation and its interaction with other key characteristics of intercropping, i.e., crop type combination, N fertilizer, relative density, and intercropping pattern, using data from the intercropping literature. Quantile regression characterizes the entire distribution of the response metric by estimating quantiles of this distribution. This method gives a comprehensive characterization of the diversity of the response in the population. In this study, the effect of temporal niche differentiation on the LER was positive and significant across all quantiles (10, 15, …, 85, 90%). The response of the LER to temporal niche differentiation was similar in C3 –C3 and C3 –C4 intercrops except at low quantiles (below 20%), where a stronger response was found in C3 –C4 than in C3 –C3 intercrops. There was a negative effect of N fertilizer on the LER in the absence of temporal niche differentiation at all tested quantiles. At low LER (quantiles </p

Global analysis of nitrogen fertilization effects on grain zinc and iron of major cereal crops

Human zinc (Zn) and iron (Fe) deficiencies can partly be alleviated by enhancing cereal concentrations of these micronutrients. Soil nitrogen (N) levels codetermine cereal grain yields and Zn and Fe nutrition of plants and grains. Grain Zn and Fe concentrations have been reported to be affected by both yield dilution and enhanced acquisition and grain allocation of Zn and Fe. A global meta-analysis of 100 publications concerning wheat, maize, and rice providing 785 records of Zn and 506 records of Fe allowed us to assess their relative importance and quantify the concentrations and bioavailability of Zn and Fe in major cereal grains over a wide range of N fertilization levels. Compared with the no N controls, N application significantly increased grain Zn and Fe concentrations in all crops except maize Zn. The increase in grain protein concentration correlated positively with the increases in Zn and Fe concentrations in all cereals except Zn in maize. In rice, the grain Zn and Fe concentration increase was independent of the rate of N applied. Grain concentrations of Zn and Fe in wheat and Fe in maize were positively correlated with N rate but were only higher than those in the controls above 40–60 kg N ha−1. At lower N rates, the dilution effect was thus stronger than the enhancement effect. N supply had a larger effect on Zn and Fe concentrations in loamy textured soils or at lower soil available N and phosphorus (P), or higher soil organic matter and available Zn contents or with P and Zn fertilization, but the effect sizes differed among crops. Reductions in phytic acid concentration after N fertilization occurred in wheat, potentially improving micronutrient bioavailability. Thus, our findings indicate that N fertilization could be managed in ways that simultaneously support high grain yields and enhance nutritional quality for major cereals