Biomass and nutrient accumulation by cover crops and upland rice grown in succession under no-tillage system as affected by nitrogen fertilizer rate.

Cover plants are intended to cover the soil, protecting it from erosion, nutrient leaching, and providing nutrients through recycling or biological fixation. The objectives of this study were to evaluate the dry biomass productivity and total accumulation of nutrients in the cover crops shoots and in the upland rice grown in succession; and evaluate the effect of the isolated and combined use of cover crops and urea on upland rice crop, grown under no-tillage system. The field experiment was conducted at Selvíria-MS, Brazil, in an Oxisol (Rhodic Haplustox), cerrado (savannah) phase. The experimental design was randomized blocks, in a 5x3 factorial scheme. The treatments were four cover crops species: sunn hemp (Crotalaria juncea L.), pigeon pea (Cajanus cajan L.), green velvet bean (Mucuna prurens), millet (Pennisetum glaucum L.), and spontaneous vegetation (fallow in off-season) combined with 20 kg N ha-1 applied at sowing, 20 kg N ha-1 applied at sowing + 60 kg N ha-1 at plus topdressing, and without mineral N fertilizer application. The millet recycled large amounts of K, Mg, S, and micronutrients, but negatively influenced the rice grain yield grown in succession. There was no response to topdressed mineral N fertilizer when the crop was grown in rotation to legume cover crops. Upland rice under no-tillage showed a positive response to the N fertilization at seeding and when it is grown in rotation with the use of millet or fallow in the off-season. Upland rice also showed a response to N fertilization applied at topdressing

Hydrological influence on the evolution of a subtropical mangrove ecosystem during the late Holocene from Babitonga Bay, Brazil

Mangroves are key ecosystems which respond to global changes in tropical and subtropical regions worldwide. We describe late Holocene mangroves that established close to the southernmost limit (28°S) for this type of ecosystem in South America. Our findings are based on a C dated core obtained from Babitonga Bay, Santa Catarina State, Brazil (26°12′S, 48°33′W). Analysis of palynology, sedimentary facies, isotopic and elemental data shows that mangrove establishment took place ~500 yrs. B.C.E., following an increase in humidity, and expanded further during the Roman Warm Period and at the end of Dark Age Cold Period. Mangrove and precipitation proxies records appear to be sensitive to rainfall patterns imposed both by the expansion/retraction of the Intertropical Convergence Zone and also the interaction with the South Atlantic Subtropical Anticyclone which affects coastal region due to sea surface temperature variations.The authors thank the Coastal Dynamic Laboratory (LADIC-UFPA) , C-14 Laboratory of the Center for Nuclear Energy in Agriculture (CENA-USP) , University of Joinville (UNIVILLE) and Radiocarbon Laboratory (LAC-UFF) for all infrastructure and support. We also thank three anonymous Reviewers and Prof. H. Falcon-Lang for their constructive comments. The first and third author thanks Brazilian Council for Technology and Science-CNPq for fellowship (process 131813/2016-1 , 165911/2015-8 and 305074/2017-2 ). This study was financed by CNPq ( 445111/2014-3 , 405060/2013- 0 ) and FAPESP ( 2011/00995-7 , 2017/03304-1, and 2020/13715-1 ). This study also was financed in part by the Coordenação de Aperfeiçoamento de Pessoal Nível Superior – Brazil (CAPES) – Finance Code 001

SYNTHESIS OF N-15-ENRICHED UREA (CO((NH2)-N-15)(2)) FROM (NH3)-N-15, CO, AND S IN A DISCONTINUOUS PROCESS

CO((NH2)-N-15)(2) enriched with the stable isotope N-15 was synthesized based on a reaction involving CO, (NH3)-N-15, and S in the presence of CH3OH. The method differs from the industrial method; a stainless steel reactor internally lined with polytetrafluoroethylene (PTFE) was used in a discontinuous process under low pressure and temperature. The yield of the synthesis was evaluated as a function of the parameters: the amount of reagents, reaction time, addition of H2S, liquid solution and reaction temperature. The results showed that under optimum conditions (1.36, 4.01, and 4.48 g of (NH3)-N-15, CO, and S, respectively, 40 ml CH3OH, 40 mg H2S, 100 degrees C and 120 min of reaction) 1.82 g (yield 76.5%) of the compound was obtained per batch. The synthesized CO((NH2)-N-15)(2) contained 46.2% N, 0.55% biuret, melting point of 132.55 degrees C and did not exhibit isotopic fractionation. The production cost of CO((NH2)-N-15)(2) with 90.0 at. % N-15 was US$ 238.60 per gram.Foundation for Research Support of the State of Sao Paulo (FAPESP)Foundation for Research Support of the State of Sao Paulo (FAPESP

In search of meaningful work on digital freelancing platforms: the case of design professionals

Growth of the platform economy has been accompanied by critiques of the fragmented, isolated and precarious nature of the employment it offers. Yet, little is known about how creative freelancers perceive the meaning of work on the platforms. Based on 40 interviews with freelancers, clients, platform owners and industry experts, this paper reveals that most freelancers are concerned about how operating through the platform, and their dependence on it, is undermining the meaningfulness of their work. Freelancers find that the platforms are eroding both the manifest (i.e. monetary) and latent (i.e. non‐monetary) meaning of their work although they are mostly concerned about the latent element of meaning. The analysis reveals that the small group of freelancers who pursue meaningful work and earn a sustainable income on platforms are those with strong entrepreneurial orientation