Hugo Escobar’s research while affiliated with University of Tarapacá and other places

Northern Chile has scarce water resources due to the Atacama Desert. Thus, water obtained from The Andes range has great interest. This study analyzes the effect of different amounts of irrigation water on gas exchange, seed yield, biomass and water use efficiency in two chia (Salvia hispanica L.) phenotypes, white and black. We performed measurements during flowering and at physiological maturity. The experiment was installed in field conditions under three water regimes: 100, 70 and 40% of the evapo-transpiration portemntial (ETo). No significant differences were found in gas exchange parameters among treatments, but there were differences between sampling times, decreasing as a function of senescence. Intrinsic water use efficiency (WUE-intr) was not different between treatments or on the two measuring dates in either phenotype, except for black in the treatment with least water. The water use efficiency in biomass production (WUE-biomass) did not show significant differences between treatments in either phenological stage. Seed yield was not significantly different between treatments in white chia, while in dark chia seed yield increase was directly related to water availability. In both phenotypes, the WUE referring to seed yield (WUE-seed) was significantly greater in plants with less water availability.

Chia (Salvia hispanica L.) is a species with seeds that have high essential fatty acid content, which has encouraged increased crop production worldwide. However, the expansion of chia is limited because it is a photoperiodsensitive plant adapted to areas without cold. The objective of the present study was to determine the effect of different climatic conditions on the growth, grain yield and oil production of chia under irrigation in three geographic areas of Chile: Valle de Azapa (18°30’ S lat) with a coastal desert climate, normal desert climate in Canchones (20°26’ S lat), and Las Cruces (33°30’ S lat) with dry Mediterranean climate with marine influence, and two chia phenotypes: white and dark. Results indicated that desert conditions in the Valle de Azapa (VA) and Canchones (CH) provided better conditions for plant growth; the highest yield (> 2900 kg ha-1) and oil production (> 550 L ha-1). In Las Cruces (LC), at higher latitude, low temperatures present beginning in April coincided with the reproductive stage, affecting yield which was no more than 129 kg ha-1; thus this zone is not recommendable for chia cultivation. This study also determined an 11.8 h day length threshold for the beginning of flowering; when plants are exposed to shorter days flower initiation is more precocious, but when day length is not adequate plants only begin to flower when they have accumulated 600-700 ºC d.

Date palm was introduced to South America, probably from Morocco, by Spanish colonialists to the central coast of Peru, from where it spread to Mexico and North America. Currently, date palm is little known as an agronomic crop; its cultivation in South America is limited to specifi c areas of Peru, Chile, Argentina, and Brazil. Excellent climatic conditions for date palm cultivation are present in northern Chile from Arica to Copiapó, as well as in areas of central and northern Peru such as Ica, Zaña, and Pisco. Important germplasm has developed from seed propagation which has produced all the named cultivars such as Medjool, Zahidi, and Deglet Noor. The importance of seedling-derived material lies in its adaptation to edaphic and climatic conditions different from those found in its area of origin, including acquisition of tolerance to high levels of salinity and boron in soil and irrigation water. It is interesting that there are date palms cultivated in locations at 1,500 m elevation such as the valleys of Pisco and Ingenio in Peru and Codpa in Chile. Currently, date production in Chile and Peru is all consumed locally. As well as having areas with optimal climate for the cultivation of date palms, Chile and Peru have important strengths and opportunities for the development of this crop, such as internationally recognized prestige in the production and exportation of fruit, government support of innovation, and multiple free trade agreements. There are also weaknesses, mainly the absence of local agronomic researchers familiar with the crop, lack of trained workers, insuffi cient knowledge about this fruit, and limited consumption. Date palm has an important potential in South America due to favorable agricultural and economic conditions as well as an expanding international demand.

The objective of this study was to analyze the effect of saline-boron stress on the vegetative growth, dry leaf weight, water potential (Ψw), relative water content, and leaf and root B and Cl- contents in 8 accessions of olive. Rooted one-year-old plants were cultivated for 132 days with 50% shading in 5-L pots containing sand substrate and watered with Jensen's nutrient solution. After eight days of uniform ferti-irrigation, the plants were exposed to saline-boron stress, which was administered in three successive stages to condition them to a final stress of 0.49 mM B(OH)3 and 200 mM NaCl. The accessions were identified by their place of origin as Suca, Chiza, San Pedro I (SPI), Taltal, Azapa, San Pedro II (SPII), Frantoio and Lluta. The results showed that saline-boron stress decreased vegetative growth and dry matter in all accessions. The levels of Cl- in leaves and roots increased significantly, although Suca and SPI experienced the least increases. B increased in leaves and roots but did not reach toxic levels. Water potential decreased except in the accession Taltal. RWC decreased in all accessions. Cv. Frantoio, known internationally for its high salt tolerance, was used as a reference for the observed responses in the other accessions.

To understand the effect of biochar, identify its presence and quantify its stability in soil, it is necessary to differentiate between the two main sources of carbon. These sources are resident soil organic matter and biochar, which is produced by burning organic matter under low oxygen concentration in a process known as pyrolysis. The present study employs solid-liquid extraction with an alkaline solution, the efficiency of which was improved by a reflux system and quantification using the modified Walkley-Black method, to distinguish the two carbon sources in samples of arid soils from the area surrounding the city of Arica, XV region of Chile. The mean annual precipitation of this area is less than 0.4 mm, and its soils are characterized by high salinity, low organic matter content, high porosity and low bulk density. The values for total extracted organic carbon obtained using this method were very similar to those for the resident soil organic carbon, indicating that the technique extracts mostly resident soil organic carbon and not biochar carbon. Biochar carbon represented less than 6% of the total organic carbon extracted by the method. The results demonstrate that this method can quantitatively differentiate between resident total organic carbon and applied biochar carbon. The method thus represents a valuable alternative to the use of an elemental analyzer.

N. Lara, L. Figueroa, F. Carvajal, Y. Zapata, C. Urbina, and H. Escobar. 2013. Quantitative differentiation between soil organic carbon and biochar carbon in Aridisol. Cien. Inv. Agr. 40(2): 387-395. To understand the effect of biochar, identify its presence and quantify its stability in soil, it is necessary to differentiate between the two main sources of carbon. These sources are resident soil organic matter and biochar, which is produced by burning organic matter under low oxygen concentration in a process known as pyrolysis. The present study employs solid-liquid extraction with an alkaline solution, the efficiency of which was improved by a reflux system and quantification using the modified Walkley-Black method, to distinguish the two carbon sources in samples of arid soils from the area surrounding the city of Arica, XV region of Chile. The mean annual precipitation of this area is less than 0.4 mm, and its soils are characterized by high salinity, low organic matter content, high porosity and low bulk density. The values for total extracted organic carbon obtained using this method were very similar to those for the resident soil organic carbon, indicating that the technique extracts mostly resident soil organic carbon and not biochar carbon. Biochar carbon represented less than 6% of the total organic carbon extracted by the method. The results demonstrate that this method can quantitatively differentiate between resident total organic carbon and applied biochar carbon. The method thus represents a valuable alternative to the use of an elemental analyzer.

We analyzed the mitigating effect of NO3 - and salicylic acid (SA) on the detrimental effects of salt stress by studying the water status of plants of maize grown in Hoagland's medium with NaCl 100 mM as the saline component, to which SA and NO3 - were added in different concentrations as mitigating agents. We evaluated water potential Ψw, osmotic potential Ψs, relative water content (RWC), turgor potential (Ψp ), and the osmotic adjustment (OA) of leaves and roots. SA 0.5 mM mitigated the effects of salinity by increasing the Ψs of the leaf, the Ψsof theroot, the Ψpof the leaf, RWC and OA of the leaf; while NO3 was only effective in combination with SA, mitigating the effects of salinity by increasing RWC and OA. However, the interaction SA-NO3 reduced leaf Ψw and Ψs of leaves and roots. Mtigation of salt stress was also detected by a positive effect on plant growth. The greatest effect on growth was produced by the NO3 treatments and SA 0.5 mM combined with NO3.

and L. Cardemil. 2010. Mitigating effect of salicylic acid and nitrate on water relations and osmotic adjustment in maize, cv. Lluteño exposed to salinity. Cien. Inv. Agr. 37(3): 71-81. We analyzed the mitigating effect of NO 3 -and salicylic acid (SA) on the detrimental effects of salt stress by studying the water status of plants of maize grown in Hoagland´s medium with NaCl 100 mM as the saline component, to which SA and NO 3 -were added in different concentrations as mitigating agents. We evaluated water potential (Ψ w), osmotic potential (Ψ s), relative water content (RWC), turgor potential (Ψ p), and the osmotic adjustment (OA) of leaves and roots. SA 0.5 mM mitigated the effects of salinity by increasing the Ψ w of the leaf, the Ψ s of the root, the Ψ p of the leaf, RWC and OA of the leaf; while NO 3 -was only effective in combination with SA, mitigating the effects of salinity by increasing RWC and OA. However, the interaction SA-NO 3 -reduced leaf Ψ w and Ψ s of leaves and roots. Mitigation of salt stress was also detected by a positive effect on plant growth. The greatest effect on growth was produced by the NO 3 -treatments and SA 0.5 mM combined with NO 3 -.