Building resilience against drought and soil erosion: impact of field water conservation in the drought prone Vertisol areas of northern Ethiopia

Field water conservation practices are a way forward to build resilience against drought through increasing productive green water and crop yield, while reducing runoff (blue water) and soil erosion. A long-term tillage experiment was carried out (2005 to 2011) on a Vertisol to quantify the impact of field water conservation practices on soil moisture, runoff, soil loss and crop yield in a rainfed field in northern Ethiopia. The experimental layout was a randomized complete block design with three replications on permanent plots of 5 m by 19 m. The tillage treatments were (i) derdero+ (DER+) with a furrow and permanent raised bed planting system, 30% standing crop residue retention and no-tillage on top of the bed, (ii) terwah+ planting system (TER+) with ploughing once at sowing, 30% standing crop residue retention and fresh broad beds, and (iii) conventional tillage (CT) with a minimum of three tillage operations and removal of crop residues. The crops grown in rotation were wheat, barley, teff and grass pea. The field conservation practices thus combined indigenous conservation practices (derdero and terwah) with the concepts of conservation agriculture (hence the ‘+’). Data on soil loss, runoff, soil moisture, crop yield and NDVI were collected. Significantly different (p<0.05) mean soil losses of 4.4, 12.5 and 18 t/ha/y were recorded for DER+, TER+ and CT, respectively. Similarly, the mean runoff was 458, 706 and 925 m3/ha/y from treatments with DER+, TER+ and CT, respectively. The average grain yield of wheat over three years was 2.46, 2.02 and 1.61 t/ha for DER+, TER+ and CT, respectively. NDVI records in wheat and grass pea were higher in DER+

Brazilian Consensus on Photoprotection

Brazil is a country of continental dimensions with a large heterogeneity of climates and massive mixing of the population. Almost the entire national territory is located between the Equator and the Tropic of Capricorn, and the Earth axial tilt to the south certainly makes Brazil one of the countries of the world with greater extent of land in proximity to the sun. The Brazilian coastline, where most of its population lives, is more than 8,500 km long. Due to geographic characteristics and cultural trends, Brazilians are among the peoples with the highest annual exposure to the sun. Epidemiological data show a continuing increase in the incidence of nonmelanoma and melanoma skin cancers. Photoprotection can be understood as a set of measures aimed at reducing sun exposure and at preventing the development of acute and chronic actinic damage. Due to the peculiarities of Brazilian territory and culture, it would not be advisable to replicate the concepts of photoprotection from other developed countries, places with completely different climates and populations. Thus the Brazilian Society of Dermatology has developed the Brazilian Consensus on Photoprotection, the first official document on photoprotection developed in Brazil for Brazilians, with recommendations on matters involving photoprotection

Lawson criterion for ignition exceeded in an inertial fusion experiment

For more than half a century, researchers around the world have been engaged in attempts to achieve fusion ignition as a proof of principle of various fusion concepts. Following the Lawson criterion, an ignited plasma is one where the fusion heating power is high enough to overcome all the physical processes that cool the fusion plasma, creating a positive thermodynamic feedback loop with rapidly increasing temperature. In inertially confined fusion, ignition is a state where the fusion plasma can begin "burn propagation" into surrounding cold fuel, enabling the possibility of high energy gain. While "scientific breakeven" (i.e., unity target gain) has not yet been achieved (here target gain is 0.72, 1.37 MJ of fusion for 1.92 MJ of laser energy), this Letter reports the first controlled fusion experiment, using laser indirect drive, on the National Ignition Facility to produce capsule gain (here 5.8) and reach ignition by nine different formulations of the Lawson criterion

Iron Behaving Badly: Inappropriate Iron Chelation as a Major Contributor to the Aetiology of Vascular and Other Progressive Inflammatory and Degenerative Diseases

The production of peroxide and superoxide is an inevitable consequence of aerobic metabolism, and while these particular "reactive oxygen species" (ROSs) can exhibit a number of biological effects, they are not of themselves excessively reactive and thus they are not especially damaging at physiological concentrations. However, their reactions with poorly liganded iron species can lead to the catalytic production of the very reactive and dangerous hydroxyl radical, which is exceptionally damaging, and a major cause of chronic inflammation. We review the considerable and wide-ranging evidence for the involvement of this combination of (su)peroxide and poorly liganded iron in a large number of physiological and indeed pathological processes and inflammatory disorders, especially those involving the progressive degradation of cellular and organismal performance. These diseases share a great many similarities and thus might be considered to have a common cause (i.e. iron-catalysed free radical and especially hydroxyl radical generation). The studies reviewed include those focused on a series of cardiovascular, metabolic and neurological diseases, where iron can be found at the sites of plaques and lesions, as well as studies showing the significance of iron to aging and longevity. The effective chelation of iron by natural or synthetic ligands is thus of major physiological (and potentially therapeutic) importance. As systems properties, we need to recognise that physiological observables have multiple molecular causes, and studying them in isolation leads to inconsistent patterns of apparent causality when it is the simultaneous combination of multiple factors that is responsible. This explains, for instance, the decidedly mixed effects of antioxidants that have been observed, etc...Comment: 159 pages, including 9 Figs and 2184 reference

Conservation agriculture for wheat-based cropping systems under gravity irrigation: increasing resilience though improved soil quality

A field experiment was conducted under furrow irrigation on a Vertisol in arid northwestern Mexico, to evaluate sustainable production alternatives for irrigated wheat systems. Treatments included: tillage (conventionally tilled raised beds where new beds are formed after disc ploughing before planting [CTB] and permanent raised beds [PB]) and irrigation regimes (full and reduced). Physical and chemical soil quality was compared among treatments. PB improved soil structure and direct infiltration, increased topsoil K concentrations (0–5 cm; 1.6 cmol kg−1 in PB vs. 1.0–1.1 cmol kg−1 in CTB) and reduced Na concentrations (0–5 cm; 1.3–1.4 cmol kg−1 in PB vs. 1.9–2.2 cmol kg−1 in CTB) compared to CTB. Crop growth dynamics were studied throughout the season with an optical handheld NDVI sensor. Crop growth was initially slower in PB compared to CTB, but this was compensated by increased crop growth in the later stages of the crop cycle which influenced final yield, especially under reduced irrigation. These results were reflected in the final grain yield: in the third year after conversion to PB, no difference in grain yield was found between tillage systems under full irrigation. However, under reduced irrigation the improved soil quality with PB resulted in a 19% and 26% increment in bread and durum wheat grain yields, respectively. As projected climatic scenarios forecast higher evapotranspiration,less reliable rainfall and increased drought, our results indicate that PB could contribute to maintaining and increasing wheat yields in a sustainable way

Influence of tillage, residue management, and crop rotation on soil microbial biomass and catabolic diversity

The densely populated, intensively cropped subtropical highlands of the world have agricultural sustainability problems from soil erosion and fertility decline. In 1991, the International Maize and Wheat Improvement Center (CIMMYT) initiated a long-term field experiment at its semi-arid highland experiment station in Mexico (2240 masl; 19.318N, 98.508W; Cumulic Phaeozem) to investigate the long-termeffects of tillage/seeding practices, crop rotations, and crop residue management on maize and wheat grown under rainfed conditions. Soil ecology status contributes to agricultural system sustainability, and evaluations were made to determine the effect of different management practices on soil microbial biomass (SMB) (substrate-induced respiration (SIR) and chloroform fumigation incubation (CFI)) and micro-flora physiological and catabolic diversity (BIOLOGTM ecoplate well system). SMB-C (CFI, SIR) was significantly and respectively 1.2 and 1.3 times higher for residue retention (average 387mg C kg1 dry soil and 515 mg C kg1 dry soil, respectively) compared to residue removal. SMB-C (CFI) was significantly higher for wheat (369mg C kg1 dry soil) compared to maize (319mg C kg1 dry soil). SMB-N (CFI) was significantly 1.3 times higher for residue retention (average 28mg N kg1 dry soil) compared to residue removal. The average well color development (AWCD) obtained by the BIOLOGTM ecoplate essay indicated there were large differences in the catabolic capability of soil microbial communities after 15 years of contrasting management practices. While maize and wheat rotation under conventional tillage with residue retention showed a significantly higher overall AWCD value compared to the other treatments, AWCD ofmaize with zero tillage and residue removal was significantly lower than in the other treatments. AWCD was significantly higher for residue retention compared to residue removal and for wheat as compared to maize. For maize, the management practices were divided into two groups; zero tillage with residue removal was separate from all other treatments. For wheat, conventional tillage was separate from all zero tillage treatments. This study suggests that in the target area, a cropping system that includes zero tillage, crop rotation, and crop residue retention can increase overall biomass and micro-flora activity and diversity compared with common farming practices. In the long term, zero tillage combined with residue retention creates conditions favourable for the development of antagonists and predators, and fosters a new ecological stability. Zero tillage without residue retention is an unsustainable practice that leads to poor soil health in the long run.status: publishe

Short term changes in dynamics of C and N in soil when crops are cultivated on permanent raised beds

Densely populated, intensively cropped highland areas in the subtropics are prone to erosion and declining soil fertility, making agriculture unsustainable. Permanent raised bed planting systems, as a form of conservation agriculture, have been developed to reduce production costs while conserving resources and sustaining the environment. In 2004, a new experiment with long term focus was started under rain fed conditions at El Batan (Mexico; 2,240 m a.s.l.; 19.31N, 98.50W; Cumulic Phaeozem), which aims at understanding the effects of (1) tillage (conventionally tilled or permanent raised beds), (2) residue management (retention or removal) and (3) N fertilizer application (0 or 120 kg N/ha) on N availability in a yearly maize/wheat rotation system. Incubation experiments were conducted to establish how the different treatments affect C and N dynamics in the soil. Tillage increases the availability of soil organic matter by soil aggregate disruption, enhancing C and N mineralization. Conventionally tilled raised beds with incorporation of crop residues increased the CO2 production rate. In both tillage systems, retention of maize or wheat residue without N fertilizer application led to N immobilization. In permanent raised beds, however, the immobilization due to residue retention could be compensated by application of N fertilizer, while conventionally tilled raised beds appeared to use the applied N fertilizer less efficiently.status: publishe

Effects of conservation agriculture on runoff, soil loss and crop yield under rain fed conditions in Tigray, Northern Ethiopia

The aim of conservation agriculture (CA) is to improve soil quality and crop yield whilst reducing runoff and topsoil erosion. An experiment was carried out in a rainfed field using a permanent raised bed planting system for 3 yr (2005–2007) in Adigudem, northern Ethiopia in order to evaluate the effect of CA on runoff, soil loss and crop yield. CA practices were introduced in fields with Vertisols in a randomized complete block design on permanent 5 · 19 m plots. Three treatments were evaluated: (1) conventional tillage (CT) with a minimum of three tillage operations and removal of crop residues, (2) terwah (TER) that was similar to CT except that contour furrows were included at 1.5 m intervals, and (3) derdero+ (DER+), which consists of permanent raised beds with a furrow and bed system, retention of 30% of standing crop residues and zero tillage on the top of the bed. All ploughing as well as the maintenance of the furrows of the permanent raised beds was done using a local ard plough called maresha. Results from monitoring over 3 yr showed that soil loss and runoff were significantly higher (P < 0.05) in CT followed by TER and DER+. Average soil losses of 5.2, 20.1 and 24.2 t ⁄ ha were recorded from DER+, TER and CT, respectively. Runoff was 46.3, 76.3 and 98.1 mm from DER+, TER and CT, respectively. Grain yield was significantly lower (P < 0.05) in DER+ under teff in 2006, probably due to the high sensitivity of teff to weeds. The yield of wheat in 2007 was significantly higher in DER+ followed by TER. The terwah system is recommended as a first measure for wider adoption to reduce runoff and soil loss and to increase crop yield. The long-term goal is to achieve a derdero+ system, i.e. a permanent raised bed planting system along with the application of crop residues.status: publishe