Celosia cristata L. is a tropical, herbaceous, annual species belonging to the family Amaranthaceae. Biostimulants produced with the alga Ascophyllum nodosum have provided positive effects on plant development. The objective of this work was to evaluate the effects of Ascophyllum nodosum biostimulant application on seedling production, vegetative growth and flowering of Celosia cristata plants. The experiment was carried out in two stages, in a greenhouse, as a completely randomized design, with five replications. In the first stage, treatments consisted of applications of 0 (water); 0.6; 0.8 and 1.0 mL L-1 of biostimulant with Ascophyllum nodosum, applied to the seedlings, seven days after emergence, in trays. At 21 days after the application of the treatments, the following were evaluated: seedling height, leaf number and root length. In the second stage, carried out in 1.5L containers, the following doses were used: 0 (water); 1.0; 1.5 and 2.0 mL L-1 of biostimulant with Ascophyllum nodosum, applied to the plants, at 7 and 37 days after transplantation, and plant height, leaf area, days at flowering and dry mass of inflorescences were evaluated. The results obtained in the two stages were submitted to analysis of variance and regression. The use of Ascophyllum nodosum biostimulant did not provide satisfactory results in the stage of seedling production, vegetative growth and flowering of Celosia cristata under the conditions of this experiment. The doses of biostimulant used in this research caused reduction of growth and lower mass of inflorescences.

Onion plants (Allium cepa L.) have a low competitive capacity against weeds, so these must be controlled from the beginning of the crop cycle. Plant communities respond differently to the management practices used in the fore crops (eg. tillage and fertilization). The objective was to evaluate the effect of different fore crops on the weed communities in direct seeding onion crops. During the 2015/16 season, an onion crop was implanted in the Lower Valley of the Rio Negro by direct seeding in plots with different fore crops: tomato, soybean, corn and carrot. The emergence of weeds was evaluated 15 and 45 days after sowing (DAS). The weeds on the ridge were collected in a 30 x 30 cm frame to determine the number and biomass for each species, and to calculate the richness and diversity. Ten weed species were observed in a cotyledonal state at 15 DAS, without differences between treatments. At 45 DAS, Lamium amplexicaule L., Xanthium spinosum L., Polygonum aviculare L., Picris echinoides L., Sonchusasper L. and Echinochloa crus-galli L. were the most frequent species. The greatest richness, density and diversity was observed after rotation with tomato. The differential response of the weeds to the fore crops would help design the rotations for more efficient weed control in an onion crop.

Argentina, one of the main South American strawberry (Fragaria x ananassa) producers, shows an increasing trend to reduce the use of agrochemicals (pesticides and fertilizers), and incorporate bio-inputs. In this context, the objective of this work was to evaluate the effect of MO.14 (a liquid organic amendment, rich in humic and fulvic acids), applied alone or combined with a biological activator (Biomix), on the yield and fruit quality of four strawberry cultivars. A trial was carried out in the 2016 productive season and part of 2017, in Famaillá (Tucumán). Treatments: MO.14 (drench), MO.14 (drench) + Biomix (foliar) and untreated control (T). Cultivars: Benicia, Camino Real, Merced and San Andreas. Yield (total fruit weight/plant, Yld), number of fruits/plant (NF), marketable fruit average weight (MFAW) and percentage of rotten fruits (%RF) were evaluated. Experimental design: CRD with three replications of 30 plants per cultivar and treatment. Data were subjected to ANOVA. Treatments improved Yld and NF, but not %RF and MFAW (genotypic effects prevailed). MO.14 showed Yld and NF values higher than MO.14 + Biomix. Treatment-cultivar interactions were significant for NF. Regarding the cultivars, Merced stood out (Yld, MFAW). In May 2017, when the first harvests of the 2nd year started, biostimulants exceeded T in Yld. Biostimulant treatments could reduce the use of chemical fertilizers in strawberry, contributing to agroecosystem sustainability, although new studies (dose, concentration, number of applications) should validate that.

Sustainability indicators applied to agricultural production systems are useful tools to reverse critical situations. However, sustainability assessment methodologies are not widely applicable. The objective of this paper is to elaborate a methodological proposal to preliminarily assess sustainability in horticultural systems of the southeast of the province of Buenos Aires and especially of the productive periurban area of the city of Mar del Plata (General Pueyrredon district). Assuming a technical-professional approach and from the integration of inductive and deductive methods, background studies, direct observations and semi-structured interviews with key informants, criteria, indicators and categories applicable to the area of study were defined. Then, preliminary applications were made to two cases of the periurban area of Mar del Plata with different types of production: conventional and in agroecological transition. It is expected with this methodological proposal to provide a useful tool to identify the critical aspects in the development of horticultural activities in the periurban area of Mar del Plata and in the region, in order to revert situations of environmental conflict and contribute with strategies aimed at sustainability.