Root distribution, nutrient uptake, and yield of two upland rice cultivars under two water regimes

Upland rice (Oryza sativa L.) cultivation has been increasing in global importance due to the decreasing water availability for flood- irrigated rice. The use of sprinkler irrigation to supplement rainfall and the identification of cultivars more adapted to lower water availability could be effective alternatives for producing upland rice without yield losses while using less water. The objective of this field study was to evaluate the root distribution, plant nutrition, and grain yield of two drought tolerant upland rice cultivars under two water regimes in the Cerrado Region of Brazil during two growing seasons. The main plots were two water regimes (rainfed and sprinkler-irrigation plus rainfall). Subplots were two upland rice cultivars Carajás and IAC 201. Low water availability reduced root growth by 7% and grain yields were from 2644 to 4002 kg ha-1 on average for rainfed and sprinkler irrigation treatments, respectively. Carajás had a significantly better root distribution, nutrient uptake, and higher grain yield (3732 kg ha-1) compared with IAC 201 (2914 kg ha-1) averaged over two growing seasons and water regimes. There were no treatment interactions. Our results suggest that, even when cultivars with a higher tolerance to less water availability are used, using sprinkler irrigation to augment limited rainfall during dry periods may be a viable method to increase upland rice grain yields. © 2013 by the American Society of Agronomy.

Efficacy of four irrigation needles in cleaning the apical third of root canals

This study aimed to evaluate the influence of irrigation needle gauge and design, and the final root canal diameter on the apical cleaning efficacy. Twelve human mandibular incisors were used. At different stages of root canal widening (sizes 20, 30 and 40 K-files), root canals were filled with radiopaque contrast medium. Four different needles were evaluated: 23G with side opening, 22G with apical opening, 30G with side opening and 30G with apical opening. Irrigation was carried out with 2 mL distilled water. The same tooth was radiographed with a digital system several times to assess the four types of needle in those three stages of canal widening. Pre-irrigation (canals filled with contrast) and post-irrigation (canals with remaining contrast) images were submitted to digital subtraction using the Adobe Photoshop CS4 program. Pre-irrigation (filled with contrast) and subtracted (cleaned by irrigation) areas were outlined by a trained and blinded operator using the Image Tool 3.0 software. Their ratio was calculated to express the percentage of apical cleaning in each stage of canal widening (sizes 20, 30 and 40 K-files) with each of the four needles. Data obtained were subjected to one-way ANOVA and Tukey's tests. The 30G needles with side and apical opening promoted better apical cleaning at all stages of root canal widening (p<0.05). In conclusion, smaller diameter needles were more efficacious in cleaning the apical third of the root canals, regardless of their design.

Evaluation of ornamental grasses submitted to water stress

The work was carried out at the College of Agricultural and Veterinary Sciences of the State University of São Paulo (UNESP/FCAV), Campus of Jaboticabal, Brazil, aiming to study the tolerance response to water stress and capacity of regeneration after mowing three different ornamental grasses used in Brazilian landscaping: Imperial zoysia grass (Zoysia japonica 'Imperial'), zoysia grass (Zoysia japonica) and St. Augustine grass (Stenotaphrum secundatum). The experimental design was entirely randomized in a factorial scheme 33 (three grass species: Zoysia japonica 'Imperial', Zoysia japonica and Stenotaphrum secundatum; in three water stress conditions: under full sun, with and without irrigation, and under greenhouse conditions without irrigation) with four replications per plot. The irrigation was performed using microsprinklers with a flow of 0.28 L s-1, and the grasses of all plots were mowed monthly. The evaluations were executed monthly, before mowing the grass, in the beginning of each season, that means, in October (for Spring evaluation), January (for Summer), April (for Autumn) and July (for Winter), considering the Brazilian climate conditions. The evaluated parameters were shoot height and total dry mass. The data were submitted to the variance analysis and the means were compared by the Tukey test at 5% confidence level. The grasses grown under greenhouse conditions, without irrigation, showed higher height and lower dry mass weight averages, what possibly indicates that the plants etiolated. The grasses grown under full sun, either with or without irrigation, showed a similar plant development. The S. secundatum species showed greater tolerance to water stress in October, month that followed the longest dry period. The total dry mass was gradually reduced during the experiment for all grasses grown under greenhouse conditions without irrigation; however, a great general tolerance to water stress was observed for all grasses because all of them survived along nine months without irrigation.

Effect of final irrigation protocols on microhardness and erosion of root canal dentin

The aim of this study was to evaluate the effect of final irrigation protocols (17% EDTA, BioPure MTAD, SmearClear, and QMiX) on microhardness and erosion of root canal dentin. Fifty roots were sectioned transversely at the cement-enamel junction and each root was sectioned horizontally into 4-mm-thick slices. The samples were divided into five groups (n=10) according to the final irrigation protocol: G1: distilled water (control group); G2: 17% EDTA; G3: BioPure MTAD; G4: SmearClear; and G5: QMiX. The dentin microhardness was then measured with a load of 25 g for 10 s. Initially, the reference microhardness values were obtained for the samples without any etching. The same samples were then submitted to the final irrigation protocols. A new measure was realized and the difference between before and after the procedures was the dentin microhardness reduction. In sequence, the specimens were submitted to SEM analysis to verify the dentinal erosion. The Kruskal Wallis and Dunn tests (α=5%) were used to compare the results. The dentin microhardness decreased for all final irrigation protocols. There was no significant difference between groups 2, 3, 4, and 5 (P>0.05), but this groups presented significant dentin microhardness reduction than G1 (P<0.05). In G2, occurred the highest incidence of dentinal erosion (P<0.05). 17% EDTA, BioPure MTAD, SmearClear, and QMiX promoted significant dentin microhardness reduction. © 2013 Wiley Periodicals, Inc.

Network for Cooperation in Integrated Water Resource Management for Sustainable Development in Latin America and the Caribbean No. 42

Editorial remarks.-- Open discussion: Conceptual change in regulation in a model of public service provision ; Policies and institutional frameworks for drinking water supply and sanitation ; Strategies for low-carbon development in megacities in Latin America ; Adapting to climate change in water management in the irrigation sector.-- Meetings: Towards a vision on natural resource governance for equality ; Water resources faced with uncertainty and the risk of climate change ; Regulation challenges in the water sector.-- News of the Network: Lessons to be drawn from the interprovincial Colorado River flow distribution agreement ; Rural drinking water programme in Chile ; Ecuador’s Act on Water Resources and Water Use and Exploitation.-- Internet and WWW News

An assessment of the economic impact of climate change on the water sector in Grenada

Changing precipitation patterns and temperature relate directly to water resources and water security. This report presents the findings of an assessment of the water sector in Grenada with respect to the projected impact of climate change. Grenada‘s water resources comprise primarily surface water, with an estimated groundwater potential to satisfy about 10%-15% of the present potable requirement. On the smaller islands Carriacou and Petite Martinique, domestic water is derived exclusively from rainwater catchments. Rainfall seasonality is marked and the available surface water during the dry season declines dramatically. Changing land use patterns, increase in population, expansion in tourism and future implementation of proposed irrigation schemes are projected to increase future water requirements. Economic modeling approaches were implemented to estimate sectoral demand and supply between 2011 and 2050. Residential, tourism and domestic demand were analysed for the A2, B2 and BAU scenarios as illustrated. The results suggest that water supply will exceed forecasted water demand under B2 and BAU during all four decades. However under the A2 scenario, water demand will exceed water supply by the year 2025. It is important to note that the model has been constrained by the omission of several key parameters, and time series for climate indicators, data for which are unavailable. Some of these include time series for discharge data, rainfall-runoff data, groundwater recharge rates, and evapotranspiration. Further, the findings which seem to indicate adequacy of water are also masked by seasonality in a given year, variation from year to year, and spatial variation within the nation state. It is imperative that some emphasis be placed on data generation in order to better project for the management of Grenada‘s water security. This analysis indicates the need for additional water catchment, storage and distribution infrastructure, as well as institutional strengthening, in order to meet the future needs of the Grenadian population. Strategic priorities should be adopted to increase water production, increase efficiency, strengthen the institutional framework, and decrease wastage. Grenada has embarked on several initiatives that can be considered strategies toward adaptation to the variabilities associated with climate change. The Government should ensure that these programs be carried out to the optimal levels for reasons described above. The ―no-regrets approach‖ which intimates that measures will be beneficial with or without climate change should be adopted. A study on the Costs of Inaction for the Caribbean in the face of climate change listed Grenada among the countries which would experience significant impacts on GDP between now and 2100 without adaptation interventions. Investment in the water sector is germane to building Grenada‘s capacity to cope with the multivariate impact of changes in the parameters of climate.

Network for Cooperation in Integrated Water Resource Management for Sustainable Development in Latin America and the Caribbean No. 43

Editorial remarks.-- Open discussion: Energy efficiency and economic regulation in water supply and sewerage services ; Policies and institutional frameworks for drinking water supply and sanitation.-- News of the network: The goal of food self-sufficiency of the countries of the cooperation council for de Arab States of the Gulf ; Narrowing the gaps in drinking water and sanitation: an opportunity for users ; Water Users'Organizations Act of Peru ; Commission for the Integrated management of the Tárcoles River Basin, Costa Rica ; Water and sanitation Management Unit in Panama.-- Courses: Course "Strategic aspects of irrigation".-- Internet and WWW news

Ratoon sugarcane yield integrated drip-irrigation and nitrogen fertilization

The aim of this study was to compare the use of water and nitrogen on ratoon sugarcane during irrigated and rain-fed conditions, and to assess the production potential of stalks and sugar with different rates of N-fertilizer on the subsurface drip-irrigated management. The experimental design was a randomized block with four replications for each experiment and treatments: (T1) irrigated, 0kg N ha-1; (T2) irrigated, 70kg N ha-1; (T3) irrigated, 140kg N ha-1; (T4) irrigated, 210kg N ha-1; (T5) not irrigated, 0kg N ha-1, and (T6) not irrigated, 140kg N ha-1. Biometric, technological, dry matter and yield variables were analyzed among the treatments. The irrigation system together with the application of N-fertilizer at 140kg ha-1 presented significant differences in dry matter accumulation of shoots, and for the production of stalks and sugar, respectively 94, 105 and 106%, higher when compared to the not irrigated, without N-fertilizer (T5). There was a positive and synergistic effect of irrigation with N-fertilizer on the productivity of stalks and sugar. Ratoon sugarcane irrigated with subsurface dripping had the highest yield (22Mg ha-1 of sugar) with the dosage of 140kg ha-1 N.

Large-Scale Water Productivity Assessments with MODIS Images in a Changing Semi-Arid Environment: A Brazilian Case Study

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Relationships between physiological traits and productivity of sugarcane in response to water deficit

The relationships between physiological variables and sugarcane productivity under water deficit conditions were investigated in field studies during 2005 and 2006 in Weslaco, Texas, USA. A total of 78 genotypes and two commercial varieties were studied, one of which was drought-tolerant (TCP93-4245) and the other drought-sensitive (TCP87-3388). All genotypes were subjected to two irrigation regimes: a control well-watered treatment (wet) and a moderate water-deficit stress (dry) treatment for a period of 90 days. Maximum quantum efficiency of photosystem II (F (v)/F (m)), estimated chlorophyll content (SPAD index), leaf temperature (LT), leaf relative water content (RWC) and productivity were measured. The productivity of all genotypes was, on average, affected negatively; however, certain genotypes did not suffer significant reduction. Under water deficit, the productivity of the genotypes was positively and significantly correlated with F (v)/F (m), SPAD index and RWC, while LT had a negative correlation. These findings suggest that genotypes exhibiting traits of high RWC values, high chlorophyll contents and high photosynthetic radiation use efficiency under low moisture availability should be targeted for selection and variety development in programmes aimed at improving sugarcane for drought prone environments.

Physiological changes in eucalyptus hybrids under different irrigation regimes

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Daily photosynthesis, water relations, and ion concentrations of uuonymus irrigated with treated wastewater

Euonymus japonica Thunb. (euonymus) plants were submitted for 9 months to two irrigation treatments using water from different sources: a control (C) water with electrical conductivity (EC) less than 1.2 dS.m(-1) and reclaimed wastewater (RW) with EC approximate to 4 dS.m(-1). At the end of the experiment, no differences in the total dry weight were observed between treatments, whereas the leaf dry mass increased (to the detriment of the root part in RW plants). Throughout the day, the stem water potential (Psi(stem)) of the RW plants was lower than in C, whereas stomatal conductance (g(S)) was slightly reduced in RW from 0800 HR to 1200 HR, but no significant variation in photosynthesis (P-n) or energy conversion efficiency (F'(v)/F'(m)) in photosystem II was detected through the effect of salinity. Gas exchange and fluorescence showed a tendency to increase after midday in plants treated with RW. The photosynthetic behavior and fluorescence of RW plants may have been related to the nitrogen and chlorophyll content of the leaves, confirming the resistance of the photosynthetic mechanism to salinity in this species in these conditions. The toxic effects produced by high concentrations of boron (B), sodium (Na+) and chloride (Cl-) were offset by the effect of other ions like magnesium (Mg2+), potassium (K+), and phosphorus (P) in plants irrigated with RW, thus improving their physiological status without decreasing their ornamental value.

SILICON IN ROW AND NITROGEN IN TOPDRESSING FERTILIZATION ON RICE UNDER DRY LAND AND SPRINKLER IRRIGATION CONDITIONS

The objective of this work was to evaluate the effects of silicon application adjusted with nitrogen fertilization via top-dressing on grain productivity, the silicon contents of the soil, in the plant tissue and nitrogen contents in dry and irrigated conditions. The experimental outlining was from designed blocks with subdivided parcels and four repetitions. The treatments consisted of culture system (dry and irrigated) and the under parcels by the combination of silicon (0 and 100 kg ha(-1)), in magnesium and calcium silicate form (with 23% of SiO2), and four doses of N (urea) via top-dressing (0, 30, 60 and 90 kg ha(-1)). Silicon application at sowing furrow was a viable technique because it provided significant increase in the content of this element in the root growth of rice. The application of silicon in the sowing furrow did not change the content of the element nor the nitrogen nutrition in rice plants. The nitrogen application reduced the silicon content and increased nitrogen nutrition in rice plants. Silicon application at sowing furrow provided no increase in rice grain yield. When there was no water limitation to nitrogen fertilization enhanced linearly on rice grain yield, whereas under water stress the effect of nitrogen fertilization was limited.

Interaction between N-fertilizer and water availability on borer-rot complex in sugarcane

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Chlorophyll a fluorescence in Annona emarginata (Schltdl.) H. Rainer plants subjected to water stress and after rehydration

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)