Reduced water consumption of dormant-seeded sugar beet in a semiarid climate
Dormant seeding refers to sowing spring crop species in fall. In the spring, seedlings start growing and the crop is established before spring sowing is normally completed. A dormant-seeded crop can establish quickly in spring and may escape from early season drought. A study was conducted to compare performances of dormant seeding with early and late spring seeding of sugar beet. Field experiments were carried out in the Khorasn province (NE of Iran) in 2002 and 2003 by growing a bolting resistant variety (BR1). The experiment consisted of a randomized complete block design with four replications. Dormant seeding was subjected to six irrigation treatments in addition to an early and late spring seeding. The first irrigation was applied 0, 10, 20, 30, 40 and 50 days after 60% soil moisture depletion. After harvest, root yield, sugar concentration, white sugar yield, and non-sugar components of the root samples were measured and analyzed. The results of the dormant seeding showed that root yield of sugar beet decreased with increasing delay of irrigation at the early stages of plant growth. High white sugar yield was obtained at dormant seeding without irrigation delay compared to the early seeding. No significant differences were observed for white sugar yield until three and five water withholdings in 2002 and 2003, respectively. In the second year of the experiment (2003), a relatively cold winter induced about 4.5% bolters and reduced plant population with 33% compared to the early and late spring sowing treatments. In general, white sugar yield produced in response to specific irrigation amounts for dormant-seeded treatments was higher compared to early and late seeding. However, dormant seeding cannot yet be recommended as a comprehensive agricultural practice for sugar beet and, therefore, further investigations are required to improve the quality of the beet by both agronomic techniques and new improved varieties.
Effect of drought on growth and water use of sugar beet
Summary The growth and water use of sugar beet affected by early (ED) and late (LD) drought was compared with that of irrigated (I) and unirrigated (NI) controls. Mobile shelters were used to exclude rain from ED plots during June and July, and LD plots during August and September, respectively, whereas outside these periods the ED and LD plots were irrigated as necessary. The ED treatment affected the fibrous roots severely. Many of the roots in the top 60 cm of soil died and development of the root system below this depth was slow. Expansion of the leaf canopy slowed, radiation interception was reduced and the rate of water use fell from about 1·2 times to 0·6 times Penman potential transpiration rate. The LD treatment, which was imposed when the fibrous root system was already extensive, had little effect on the fibrous roots except in the top soil. The accessible soil water was quickly depleted and the resulting stress was accompanied by earlier senescence of leaves. The rate of converting intercepted light to crop dry matter was reduced in both treatments. However, the ED treatment was the most detrimental because the amount of light intercepted in the months of highest radiation was greatly reduced owing to the restricted leaf cover. The relative effects on growth are reflected in the final sugar yields which were 8·7, 10·5, 9·9 and 12·0 (±0·30) t/ha in the ED, LD, NI and I treatments respectively. More of the deep soil water was used in the drought-affected plots (particularly LD) than in the irrigated controls. Maximum depths of water extraction were 140–150 cm in ED and I plots and > 170 cm in LD plots. The highest uptake rates per unit length of root (20–40 μl/cm per day) were measured in the deepest part of the root system. At all depths, uptake rates declined as the soil dried. After correcting for overestimated water use where necessary, the ratios of final dry matter and sugar yields respectively to season-long water use (June–October) were close to 1·4 and 0·8 t/ha per 25 mm for all four treatments.
The National PKI of Peru: a new certification hierarchy
In order to guarantee secure transactions through the Internet and to generate strong evidence that could be used in case of future legal disputes, several countries around the world have promoted and regulated the use of digital signatures based on Public Key Infrastructure (PKI). However, despite the high expectations, its implementation has achieved neither the desired results nor its globalization. Many of the reasons were discovered years ago, but they are still open problems for the scientific community nowadays. In order to consider the case of the national PKI of the Peruvian state as empirical evidence for studies that address the open problems, this article describes the details about a new certification hierarchy which is expected to overcome some of its predecessors’ limitations. It is also expected that the information disclosed in this article could be useful to other countries for making a preliminary assessment for possible cross-border recognition of Peruvian digital signatures.