Low Rainfall Conditions Research Articles

Influence of Foliar Silicic Acid Application on Soybean (Glycine max L.) Varieties Grown across Two Distinct Rainfall Years.

The foliar nutrition of silicic acid is considered to be a novel approach in enhancing the performance of many crops worldwide. The present study aimed to assess if the foliar application of silicon (Si) could influence the performance of soybean varieties with distinct crop duration, MAUS-2 (long duration) and KBS-23 (short duration). Field experiments were conducted in two consecutive years (2016 and 2017) of varied rainfall with foliar application of silicic acid @ 2 and 4 mL L−1 for three and two sprays each. The results showed significant enhancement in the yield, seed quality (protein and oil content), and uptake of nutrients (N, P, K, Ca, Mg, S, and Si) by various parts viz., seed, husk, and haulm of both varieties with foliar nutrition of silicic acid. However, the short duration variety, KBS-23, responded well under low rainfall conditions (2016) with two sprays of foliar silicic acid @ 4 mL L−1 and MAUS-2 variety in the second season under higher rainfall (2017) with three sprays of foliar silicic acid @ 2 mL L−1, along with the recommended dose of fertilizer. This research revealed that the effectiveness of foliar silicic acid nutrition differs with the duration of the varieties, number of sprays given, and water availability in the soil during the cropping period.

Genotypic selection approach made successful advancement in developing drought tolerance in perennial tree crop coconut

Coconut (Cocos nucifera L.) is a major plantation crop in humid tropics that affects the socio-economic life of several developing countries. Being a rainfed crop, coconut is highly prone to drought and breeding for drought tolerance has become a high priority research. We have identified that selection within populations as the way forward to improve drought tolerance. The current study evaluates the comparative performance of Ambakelle special (AS), a progeny of a within population selection with unselected CRIC60 to identify stable higher yielding palms for future breeding programs. Six-year yield data (2014-2019) from 110 palms in each group were evaluated. Results revealed variety, year and interaction have significant impact on annual yield (P<0.05) however, variety x year showed a non-cross-over interaction. AS recorded significant higher mean annual yield (101 nuts/palm/year) compared to CRIC60 (90 nuts/palm/year). Due to low rainfall condition prevailed from July 2016; lower nut yields were recorded for both varieties in 2017 and 2018. However, AS maintained its superiority indicating a better adaptation than CRIC60 under low rainfall conditions. Regression coefficient (bi) and mean annual yield were used in stability analysis and selected 45 palms as stable and higher yielding genotypes. Out of these 45 palms, thirty-three palms (73.3%) were from AS progeny further indicating the adaptability of AS to varying environmental conditions. Twenty palms (16 AS and 4 CRIC60) were further selected using variance of deviations from the regression (S2di) and mean kernel weight to be used in the future breeding programs for drought tolerance in coconut.

Rainfall, fire and large‐mammal‐induced drivers of Vachellia drepanolobium establishment: Implications for woody plant encroachment in Maswa, Tanzania

AbstractWorldwide, open grass areas of savannah ecosystems are being transformed into shrubland. This woody plant encroachment is likely a result of factors such as rainfall, fire and secondary dispersal by ungulate herbivory. However, few experiments have been conducted to disentangle and quantify the role of these factors for seed germination in savannahs. We assessed in situ germination success of Vachellia drepanolobium seeds under simulated rainfall variability patterns, fire treatments and dung experiments in Maswa Game Reserve, Tanzania. Fire reduced seed germination by more than 13%, whereas germination in buffalo and elephant dung increased by 1% and 3% respectively. Additionally, intermediate simulated rainfall was more beneficial for seedling emergence success than large, infrequent simulated rainfall amounts, while shoot growth was twice as high under frequent and intermediate simulated rainfall treatments than under large infrequent simulated rainfall. Our results provide insights that bush fires, drought stress, and large rainfall events can suppress V. drepanolobium seedling emergence and growth. Hence, bush encroachment may be linked to management practices such as fire regimes and climatic conditions, i.e., frequent low rainfall conditions. Our results can help predict future patterns of encroachment under varying rainfall and fire events.

Effect of rainfall and altitude on the 2-acetyl-1-pyrroline and volatile compounds profile of black glutinous rice (Thai upland rice).

The aroma intensity of rice is mixed of more than 100 volatile compounds. Fragrant rice is famous in Thailand due to specific aroma. One important volatile compound that contributes to aromatic intensity and represents a characteristic compound for fragrant rice is 2-acetyl-1-pyrroline (2AP). The production of volatile compounds and 2AP in rice is affected by various environmental factors, such as cultivation area, water content and temperature. Our research employed 29 samples of fragrant colored rice (Luempua black glutinous rice cultivar) from Phetchabun province, Thailand from three harvested rice seasons (2015-2017). The cultivation areas of rice samples exhibited differences in rainfall (976.6-1260.5 mm y r-1 ) and altitude (26.26-1033.41 m). All volatile compounds and 2AP were identified by gas chromatography-mass spectrometry (GC-MS). In 29 rice samples, 2AP levels decreased with increasing of rainfall. The increase in altitude seems to increase 2AP levels, but some high-altitude cultivation areas resulted in low 2AP content. A variety of volatile compounds was observed in 29 rice samples from different cultivation areas. The results showed that differences in altitude and rainfall affected the production of volatile compounds in fragrant colored rice. Moreover, our results indicated that different environmental conditions in cultivation areas potentially affect volatile compound production during rice growth. The increase in 2AP levels under low rainfall conditions and the assortment of volatile compound varieties produced in colored rice grown in different cultivation areas may be useful information for rice cultivation management striving to produce rice with high aromatic intensities. © 2021 Society of Chemical Industry.

Responses and Tolerance Mechanisms of Mangrove Trees to the Ambient Salinity along the Egyptian Red Sea Coast

Abstract Due to the importance of mangrove forests to the ecological system, environment, climate change adaptation, mitigation and ecosystem services, it is necessary to understand the status of the mangroves in Egypt (ecology and physiology). The present study aimed to obtain the basic information needed to evaluate the photosynthetic pigments and proline mechanisms of Avicennia marina and Rhizophora mucronata mangrove to the ambient salinity. The results reached that the free proline accumulated appreciably in leaves. The functional role of proline accumulation appears to be as a cytoplasmic osmoticum to lower cell water potential, provide hydration to bipolymer and serve as an energy source under high salinity environmental conditions. Mangroves showed variations in proline content between the two species. The highest value of proline was recorded 23.56 mg/g dry wt for R. mucronata and the minimum value was recorded 17 mg/g dry wt for A. marina. In addition, the mean value of proline was recorded 18.57 mg/g dry wt for A. marina and 23.98 mg/g dry wt for R. mucronata. The contents of chlorophyll-a in different analyzed mangroves was ranged from 4.46 to 6.05 mg/gf.wt. for A. marina, and from 3.69 to 4.29 mg/gf.wt. for R. mucronata. In addition, the chlorophyll-b content was ranged from 1.46 to 1.83 mg/gf.wt. for A. marina, and from 1.27 to 1.65 mg/gf.wt. for R. mucronata. The carotenoids contents in mangroves ranged from 2.94 to 2.29 mg/gf.wt for A. marina and from 2.04 to 2.09 mg/gf.wt for R. mucronata. In the present study, A. marina was relatively more tolerant and adapted to salinity, low rainfall and extreme temperature conditions than R. mucronata. This explains the more significant local distribution of A. marina in Egypt compared to R. mucronata.

Impact of climate change on economic components of Mediterranean olive orchards

Combining an olive growth simulation model with a specific module for economic components—namely, net margin (NM) and irrigation water productivity (IWP)—resulted in the AdaptaOlive v2.0 model. This model, used with perturbed climate (PC) and impact response surfaces (IRS), provided a tool that enabled the assessment of the impact of climate change on economic components of Mediterranean olive groves in southern Spain. Under future mild winter conditions, reductions in NM and IWP are expected; negative NM values may even be registered, with water availability having a relatively small effect on the results. In the opposite case, under future cool winter conditions, NM and IWP will increase, except for rainfed olive groves under low rainfall conditions, with water availability playing a major role. In addition, the distance (in terms of changes in temperature and rainfall compared to baseline conditions) to critical thresholds such as negative NM or IWP lower than irrigation water cost was assessed, identifying changes depending on weather conditions, water cost and olive oil price. Thus, future temperature increases of around 3 ºC under mild winter conditions could generate negative values of NM. These economic results impact the performance of adaptation strategies for olive groves, even ruling out some strategies that were previously recommended when only agronomic components were taken into account (e.g., deficit irrigation under mild winter conditions). There is thus a need for site-specific recommendations related to the use of irrigation and olive orchard management to maintain or increase the sustainability of these cropping systems. Despite the utility of using PC and IRS to achieve a scientifically sound evaluation of Mediterranean olive groves under future weather conditions, the approach presents some limitations that can be overcome using climate model outputs.

Influence of weather parameters on incidence of cowpea pod borer in central zone of Kerala

Cowpea is an annual herbaceous legume and is a main crop across Africa and Asia. It can be grown in sandy soil and is susceptible to low rainfall conditions. Cowpea pod borer (Muraca vitrata) is the main pest of cowpea. Weather factors affect different crops in many ways. Changing weather pattern over different regions affect host plants and pests. Total variability of pest populations in crops is determined by the natural growth of population and the influence of weather on activity and rate of multiplication of the insects (Kirk, 1997). Increased temperature increases productivity of cowpea if sufficient water is available, they also afford many insect species. Study conducted to examine the pest weather relationship of cowpea pod borer. Investigation was carried out on pod borer attack in cowpea [Vigna ungiculata (L.) Walp.] in five different stations of Thrissur, Kerala for three years from 2012-14. The study revealed that cowpea pod borer incidence had positive correlation with maximum temperature and diurnal temperature range, whereas, pod borer incidence showed a negative correlation with rainfall, number of rainy days and afternoon relative humidity. Step-wise regression analysis showed that maximum temperature and afternoon relative humidity experienced in prior week and rainfall and number of rainy days in prior two weeks are the significant weather factors for predicting pod borer infestation in cowpea.

Registration of ‘Devote’ soft white winter wheat

AbstractThe development of soft white winter (SWW) wheat (Triticum aestivum L.) cultivars requires numerous traits to be successfully commercialized in the low‐ to intermediate‐rainfall (&lt;400‐mm average annual precipitation) wheat production regions of the state of Washington, including winterhardiness, high grain volume weight, acceptable end‐use quality, and resistance to stripe rust, Fusarium crown rot (FCR), strawbreaker foot rot, and snow mold. Two essential traits for the low‐ to intermediate‐rainfall production regions of the state are emergence from deep planting and high grain yield under low annual rainfall conditions. ‘Devote’ (Reg. no. CV‐1170, PI 693628) SWW wheat was developed and released in March 2019 by the Agricultural Research Center of Washington State University. Devote is a semi‐dwarf cultivar adapted for the low‐ to intermediate‐rainfall wheat production regions of the state, emerges well under deep planting conditions, and is winter hardy. Devote has high‐temperature adult‐plant resistance to the stripe rust pathogen, carries the Pch1 gene for strawbreaker foot rot, is resistant to FCR and tolerant to snow mold, is intermediate in height, has late‐season maturity, and has high grain volume weight and grain yield. The end‐use quality properties of Devote are acceptable for cookie, cake, and cracker production.

Método de Penman-Monteith e Hargreaves-Samani para obtenção da ETo em ano chuvoso e seco

O planejamento e aproveitamento da água na produção agrícola, bem como o desenvolvimento de metodologias que permitam estimar o correto volume de água são fundamentais para o estabelecimento de planos eficientes de irrigação, evitando o desperdício. A evapotranspiração está diretamente relacionada ao consumo de água das plantas, desta forma, foram desenvolvidos diversos métodos para a determinação da evapotranspiração utilizando para isso, as variáveis meteorológicas. Dessa forma objetivou-se avaliar umas das metodologias mais utilizadas, que é o conhecida como método de Hargreaves-Samani para estimar a evapotranspiração de referência (ETo) em condições de baixa e elevada pluviosidade, utilizando como referência o método de Penman-Monteith-FAO56. Foram empregados dados de uma estação meteorológica automática pertencente à Universidade Federal Rural do Semi-Árido, em Mossoró (RN), os dados mencionados são referentes ao período de janeiro de 2011 a dezembro de 2012. A ETo foi estimada sendo considerada de uso prático, o modelo de Hargreaves-Samani que utiliza elementos meteorológicos de fácil obtenção como a temperatura, umidade relativa do are velocidade do vento, permitindo a estimativa da ETo é considerado de uso prático. Verificou-se que, as estimativas a partir do método de Hargreaves-Samani superestimaram os valores de ETo quando comparado com o método padrão em condições de elevada umidade para o ano de 2011, além de apresentar significância quanto a variável velocidade do vento, desta forma podendo ser fortemente influenciada por ela. Diante disso verifica-se a necessidade de calibração ou parametrização dos coeficientes da equação de Hargreaves-Samani como alternativa para uma melhor estimativa, principalmente para cidades com influência litorânea.

Response of chia (Salvia hispanica) to sowing times and phosphorus rates over two crop cycles

Chia (Salvia hispanica) is an annual oilseed crop of high nutritional value. This study aimed to analyze the performance of chia plants sown at different times and grown under different phosphorus rates. The experiment was conducted under field conditions at the Experimental Farm of the State University of Maringá, Umuarama, Brazil. Treatments were arranged in a randomized split-plot design with three replications. Phosphorus fertilizer was applied at the time of sowing at rates of 0, 40, 80, or 120 kg P2O5 ha−1. Seeds were sown on four dates at 14-day intervals, starting on March 21, 2017, for the first crop and March 29, 2018, for the second crop. Plant population density, raceme number, shoot dry matter yield, thousand seed weight, seed yield, and seed oil content were determined. It was observed that the end of March is the borderline for chia cultivation, because the low temperature and rainfall conditions occurring after this period compromise chia growth. The best phosphorous rate for chia growth was 80–120 kg ha−1, which led to optimum vegetative parameters.

Evaluation of Commercial Wheat Cultivars for Canopy Architecture, Early Vigour, Weed Suppression, and Yield

Herbicide resistance in weeds restricts control options, thereby escalating economic loss and threatening agricultural sustainability in cereal production. Field evaluation of the crop performance, competitive traits, and consequent weed suppressive potential of 13 commercial winter wheat (Triticum aestivum L.) cultivars was performed in central NSW Australia with a focus on the evaluation and modelling of above-ground interactions. In 2015 and 2016, replicated field trials were established with genetically diverse commercial wheat genotypes under moderate to low rainfall conditions in Wagga Wagga (572 mm) and Condobolin (437 mm) New South Wales, respectively. The heritage cultivar Federation and a commercial cultivar of winter cereal rye (Secale cereale L.) were included as known weed-suppressive controls. Crop and weed growth, as well as early vigour, leaf area index, and photosynthetically active radiation, were monitored at various crop phenological stages including early growth, vegetative, flowering, grain fill, and harvest. Significant differences between wheat cultivar and location were observed for crop biomass, early vigour, leaf area index, weed number, weed biomass, canopy architecture, and yield in both 2015 and 2016. Differences in weed establishment were largely impacted first by rainfall and season and secondly by crop architecture (i.e., height, size, canopy) and phenology (i.e., growth stages). Early vigour and early canopy closure were instrumental in suppressing weed establishment and growth. Cultivar performance and competition with weeds were also clearly influenced by both environmental factors and genotype, as evidenced by differences in early cultivar performance, yield, and weed suppression by season and location. Specifically, Federation, Condo, and Janz wheat cultivars were superior performers in terms of weed suppression in both locations and years; however, Federation produced up to 55% lower yield than recently introduced cultivars. Partial least squares (PLS) regression was performed to develop a predictive linear model for weed competition in commercial wheat cultivars based on weed dry biomass as the response variable and selected aboveground crop canopy traits as predictors. In 2015, the model differed in accordance with crop growth stage, but the impact of predictors on weed biomass at both locations was not significant. In 2016, under local above average rainfall conditions, the model showed a significant negative correlation (p &lt; 0.001) of most predictors on weed biomass (r2 = 0.51 at Condobolin, r2 = 0.62 at Wagga Wagga), suggesting the most influential factors in reducing weed numbers and establishment as crop vigour, biomass, and height. Our results indicate the establishment of competitive wheat cultivars in the absence of post-emergent herbicides resulted in a two to five-fold increased weed suppression over less suppressive genotypes, without significant yield penalties. Therefore, cultivar choice constitutes a cost-effective and sustainable weed management tool, particularly when weed pressure is significant.

A review of soil carbon dynamics resulting from agricultural practices

Literature related to the carbon cycle and climate contains contradictory results with regard to whether agricultural practices increase or mitigate emission of greenhouse gases (GHGs). One opinion is that anthropogenic activities have distinct carbon footprints – measured as total emissions of GHGs resulting from an activity, in this case, “agricultural operations”. In contrast, it is argued that agriculture potentially serves to mitigate GHGs emissions when the best management practices are implemented. We review the literature on agricultural carbon footprints in the context of agricultural practices including soil, water and nutrient management. It has been reported that the management practices that enhance soil organic carbon (SOC) in arid and semi-arid areas include conversion of conventional tillage practices to conservation tillage approaches. We found that agricultural management in arid and semi-arid regions, which have specific characteristics related to high temperatures and low rainfall conditions, requires different practices for maintenance and restoration of SOC and for control of soil erosion compared to those used in Mediterranean, tropical regions. We recommend that in order to meet the global climate targets, quantification of net global warming potential of agricultural practices requires precise estimates of local, regional and global carbon budgets. We have conducted and present a case study for observing the development of deep soil carbon profile resulting from a 10-year wheat-cotton and wheat-maize rotation on semi-arid lands. Results showed that no tillage with mulch application had 14% (37.2 vs 43.3 Mg ha−1) higher SOC stocks in comparison to conventional tillage with mulch application. By implementing no tillage in conjunction with mulch application, lower carbon losses from soil can mitigate the risks associated with global warming. Therefore, it is necessary to reconsider agricultural practices and soil erosion after a land-use change when calculating global carbon footprints.

Agronomic performance of grain sorghum in different spatial arrangements

Grain sorghum has been cultivated extensively in the Central-West region of Brazil in succession with soybean, since the species tolerates the low rainfall conditions recorded during this growing season. Phytotechnological adjustments for sorghum are still necessary in order to exploit the maximum yield potential of the crop. In this context, altering the plant distribution may result in better utilization of the growing area with a consequent increase in grain yield. On this basis, field experiments were conducted with two grain sorghum hybrids, replicated in two different locations, in order to evaluate the effect of the spatial arrangement of plants on the agronomic performance of grain sorghum. The design was a randomized complete block design in a 2 x 4 factorial scheme, with five replications. The factors consisted of two row spacings (0.50 and 0.25 m) and four plant densities: 120, 180, 240, and 300 thousand plants ha-1. The sorghum hybrids used were 1G244® and 1G100®. At harvest, morphological characteristics, yield components, and grain yields were evaluated. Row spacing did not influence the characteristics evaluated except for the plant height of for both hybrids, in addition to the stem diameter, tillering, and mass of a thousand grains for 1G100®. The increase in plant density provided an increase in grain yield, being the highest number of panicles per area the most expressive component for this behavior.

Coral Records at the Northern Edge of the Western Pacific Warm Pool Reveal Multiple Drivers of Sea Surface Temperature, Salinity, and Rainfall Variability Since the End of the Little Ice Age

AbstractReconstructions of key climate parameters prior to anthropogenic influences serve to constrain decadal to multicentury natural climate variability. In the western Pacific region, relatively few reconstructions exist north of the Western Pacific Warm Pool (WPWP), a region critical to global climate. In this study, we collected a coral core from Houbihu, southern Taiwan, and generated a 225‐year reconstruction of annual and wintertime sea surface temperature, dry season sea surface salinity, and wet season rainfall records derived from paired Porites Sr/Ca and δ18O profiles extending back to the end of the Little Ice Age (1850 CE). Multidecadal sea surface temperature trends generally track regional surface temperature reconstructions, indicating the dominant influence of solar and volcanic radiative forcings. Reconstructed dry season sea surface salinity reflects an advection signal linked to the East Asian Winter Monsoon and the Pacific Decadal Oscillation, both influencing variations in the Kuroshio Intrusion across the Luzon Strait. Reconstructed wet season rainfall, on the other hand, reveals influence of the Pacific Decadal Oscillation on the decadal variability of local and regional rainfall patterns. Relative to the late 1900s, our climate reconstructions document cooler and drier (high salinity and low rainfall) conditions during the end of the Little Ice Age, supporting other lines of evidence of a retracted WPWP region during this period. In the late 20th to early 21st century, our climate reconstructions record warming and freshening (low salinity and high rainfall) trends, highlighting the potential impact of anthropogenic forcing in the extension of the WPWP.

Spatial analysis of the impact of climate change factors and adaptation strategies on productivity of wheat in Ethiopia

Wheat production is expected to be challenged by future climate change. However, it is unclear how wheat grown in diverse agroecologies will respond to climate change and adaptation management strategies. A geospatial simulation study was conducted to understand the impacts of climate change and adaptation management strategies on wheat (Triticum aestivum L.) production in Ethiopia. Simulation results showed that the average long-term baseline (1980–2005) wheat yield ranged from 1593 to 3356 kg/ha. This wheat yield range is within the national average (2100–2700 kg/ha) for this decade. In regions with cooler temperatures (<21 °C), mid-century temperatures and elevated CO2, along with increased N fertilizer slightly improved attainable yield levels above 3000 kg/ha. Whereas, in regions with heat and drought conditions wheat yield declined regardless the increase of N or CO2 levels. Wheat yield increased at a diminishing rate with increase in N fertilizer rate. However, N fertilizer did not increase yields under low rainfall conditions. Two to five irrigation per season contributed to yield improvement for low rainfall locations, while yield did not substantially improve for locations receiving adequate seasonal rainfall. Therefore, based on this study, improved N fertilizer application in combination with increased CO2 could improve wheat yield under future climate in most wheat producing regions (with adequate rainfall) of Ethiopia. Our results provide valuable information regarding impacts of climate change factors and adaptation strategies for producers, researchers, extension professionals and policy makers.

Zonal Tillage as Innovative Element of the Technology of Growing Winter Wheat: A Field Experiment under Low Rainfall Conditions

Zonal tillage, including strip-till, can have a positive effect on soil properties, seed germination, plant emergence, growth, and yield of crops. The aim of this two-factor field experiment was to compare different technologies of basic soil tillage, fertilisation, and sowing of winter wheat carried out after two post-harvest agrotechnical practises in a region with low rainfall. The three treatments of the first factor were: conventional technology (CT)—plough tillage, pre-sowing fertilisation, seedbed preparation and sowing; reduced technology (RT)—plough tillage replaced with deep loosening and (ST)—one pass strip-till technology using a hybrid machine. Agrotechnical practises carried out after the harvest of the previous crop were the second factor treatments, i.e., crushed straw and shallow tillage (TS), mulch from crushed straw (MS). The measurement of the treatment effects included changes in soil moisture, plant emergence, yield components and their correlation, grain yield, and the dependence of the yield components on soil moisture. Wheat growing in ST technology resulted in a higher soil moisture than in RT and CT. Only immediately after winter was the soil moisture similar. Grain yield in ST was similar as in CT and significantly, up to 10.4%, higher than in RT. The higher ST grain yield resulted from uniform plant emergence, greater ear density, and grain weight per ear. The correlation between yield components was weaker in ST than in CT and RT. The positive dependence of the size of the crop components on soil moisture was also weaker. The agrotechnical practises performed right after the previous crop harvest affected neither the soil moisture during the growing season of winter wheat, nor the grain yield and its components.

A regional synthesis of seven-year maize yield responses to conservation agriculture technologies in Eastern and Southern Africa

In an effort to address the challenges of low crop productivity and food insecurity among Africa’s smallholder farmers, Conservation Agriculture (CA) is considered a promising strategy. This study synthesized and analyzed the maize yield merits of CA systems relative to conventional farmer practices and the contribution of agro-ecological zones, seasonal rainfall regimes and soil characteristics in five Eastern and Southern African (ESA) countries, namely Ethiopia, Kenya, Malawi, Mozambique and Tanzania, over a seven-year period. Agronomic data generated from 287 smallholder on-farm trials testing the productivity of CA cropping systems with a total of 4976 observations, were compiled and collated. Across the five countries, the factors country, cropping system, rainfall regime, agro-ecological zones and soil texture, accounted for 51, 20, 16, 10 and 3% of the yield variation, respectively. Furthermore, CA reduced yield variability by 11% (from 67% under conventional tillage to 56%). Across all the ESA environments and relative to conventional tillage with a mean of 2401 kg ha−1, CA-rotation had the highest maize yield increase (35%) compared with CA-sole (29%) and CA-intercrops (15 %) systems and thus offered the best opportunity for improved maize productivity compared with intercrops, CA-sole or conventional tilled systems. Furthermore, the highest returns (90–95%) to CA investments by smallholder farmers were realized under low rainfall conditions (<700 mm), thereby providing clear evidence of the climate smartness of CA systems under soil moisture stressed conditions. These CA yields relative to conventional till however were subdued to 26, 19 and 15% in medium-wet (700−1300 mm) and depressed even further to +1, -18 and +9% in wet (>1300 mm) environments, for CA-rotations, CA-sole and CA-intercrops, respectively. The study also showed that the most beneficial effects of CA occurred under loam textured soils. In addition, CA systems responded best (16%) on well drained soils yet depressed yields by 33% on poorly drained soils. We conclude that the prime conditions for CA performance relative to conventional tillage, involve use of CA-rotations, low rainfall (<700 mm) conditions, medium textured loam and well drained soils.

Bacterial community shifts in decomposing cowpats and the subsequent impacts on fecal source indicators for water quality monitoring

Abstract The intensification of dairy farming on the agricultural landscape in New Zealand has raised concerns about pollution sources from dairy fecal runoff into waterways. An important step for mitigation of pollution is the identification of the sources of fecal contamination. An amplicon-based metagenomic assay of the bacterial community mobilised into runoff from decomposing cowpats revealed shifts in the community composition over five and a half months of on-field decomposition. Mobilised fractions from the cowpats showed major bacterial community shifts from the anaerobic bacteria (Clostridiales and Bacteroidales) that dominate the cow rumen and fresh cowpat, to the bacterial Orders of the Actinomycetales, Sphingobacteriales and Flavobacteriales. These bacterial community shifts were in conjunction with summertime conditions of low rainfall and high sunshine hours coupled with reduced water availability. The impacts of these bacterial shifts is discussed in terms of their effects on the indicators used for water quality monitoring: the fecal indicator bacterium, Escherichia coli, and fecal source tracking (FST) markers (host-associated quantitative polymerase chain reaction (qPCR) markers and fecal steroids). The hypothesis that these bacterial community shifts would impact on the steroid ratios used as FST signatures was disproved. The fecal steroids were, therefore, reliable indicators of fecal sources from cowpats, which had been decomposing for up to five and a half months post-deposition. Consistent with the noted bacterial community changes, there were, however, concentration decreases in the bacterial groups targeted by the faecal source qPCR markers, and the E. coli mobilised from decomposing cowpats.

Production of Pearl Millet Irrigated with Different Levels of Brackish Water and Organic Matter

ABSTRACTThe objective is to determine the growth, yield and chemical characteristics of pearl millet irrigated with different levels of brackish water and organic matter in two cultivation cycles. The experimental design was randomized blocks in a 4 × 4 factorial arrangement, composed of 4 levels of brackish irrigation (25, 50, 75 and 100% evapotranspiration), 4 levels of organic matter (0, 15, 30 and 45 t ha−1) with 3 repetitions. Along two cultivation cycles, pearl millet crop was analyzed for: plant growth variables, fresh and dry mass production, water-use efficiency, and chemical composition. There was significant interaction between applied water levels and organic matter for lignin in the 2nd cut (P < .05). The number of leaves, number of dead leaves and fresh mass production were influenced by the isolated effect of brackish water levels in cut 1 (P < .05). In turn, fresh mass production, dry mass production, plant height, leaves length, panicle length, fresh mass production, crude protein and ether extract were influenced by the isolated effect of saline water levels in the 2nd cut (P < .05). Growth, biomass production and chemical composition variables in second cut are positively influenced by different brackish irrigation levels under low rainfall conditions.

Extreme and Variable Climatic Conditions Drive the Evolution of Sociality in Australian Rodents.

Climate change is generating an intensification of extreme environmental conditions, including frequent and severe droughts [1] that have been associated with increased social conflict in vertebrates [2-4], including humans [5]. Yet, fluctuating climatic conditions have been shown to also promote cooperative behavior and the formation of vertebrate societies over both ecological and evolutionary timescales [6]. Determining when climatic uncertainty breeds social discord or promotes cooperative living (orboth) is fundamental to predicting how species will respond to anthropogenic climate change. In light of this, our limited understanding of the order of evolutionary events-that is, whether harsh environments drive the evolution of sociality [6] or, alternatively, whether sociality facilitates the invasion of harsh environments [7]-and of how cooperation and conflict coevolve in response to environmental fluctuation represent critical gaps in knowledge. Here, we perform comparative phylogenetic analyses on Australian rodents (Muridae: Hydromyini) and show that sociality evolves only under harsh conditions of low rainfall and high temperature variability and never under relatively benign conditions. Further, we demonstrate that the requirement to cooperate under harsh climatic conditions generates social competition for reproduction within groups (reflected in the degree of sexual dimorphism in traits associated with intrasexual competition [8]), which in turn shapes the evolution of body size dimorphism. Our findings suggest that as the environment becomes more severe [1], the resilience of some species may hinge on their propensity to live socially, but in so doing, this is likely to affect the evolution of traits that mediate social conflict.