Tillage system and planting date effects on corn (Zea mays L.) and soybean (Glycine max L.) yield

Although tillage systems produce different soil conditions, which result in different ideal planting dates, and crops respond to planting date, most of tillage research is conducted based on a calendar date. If a tillage system by planting date interaction exists, most of the planting date recommendations based on calendar date research could change. Different authors have modified surface residue distribution in an attempt to achieve optimal soil conditions for crop growth in the row zone while maintaining optimum soil conservation conditions in the mulched interrow zone. A reasonable goal for soil management involves identifying the level of soil and residue disturbance necessary to optimize soil environmental conditions for the corn plant and residue cover for soil conservation. In order to design a tillage system that produces a residue-free band-width based on site-specific soil properties and crop needs, the use of a model to capture the effect of surface residue management, soil non-uniformities (i.e., row zone tillage), and tillage is necessary. Considering a potential tillage by planting date interaction and site-specific strip tillage opportunities, this thesis has the following objectives. The first objective is to test the performance of strip tillage, no tillage, and conventional tillage when each system is planted on the day that optimum soil temperature and water conditions for planting are reached for each system. The second objective is to conduct a soil temperature sensitivity analysis to residue-free band-width, and tillage depth with strip tillage using a model that couples water and heat transport in non-uniform soils. In a two-year study on a poorly drained soil tillage system, effects on corn yield were not detected when preestablished soil temperature and water content criteria were used to determine the day of planting each system. On the other hand, planting date has an effect on corn yield. A tillage system by planting date interaction was detected for soybean yield in one of two years, when drought conditions existed during the second half of July and August. Soil temperature, soil water content, and matric potential were most sensitive to changes in residue-free band-width at 0.05-m in both soils studied

Strip Till, No-Till and Conventional Tillage Comparisons - Does Planting Date Affect Results?

Numerous tillage studies have been conducted in Iowa, the Midwest, and throughout the U.S. with a wide range of results. The tillage system that results in the highest yield depends on several factors including soil type and weather during the study Generally, systems with little soil disturbance are favored on coarser textured soils and/or in drier years (Eckert 1987; Beyaert et al 2002). For soil and water conservation purposes, as well as for economic reasons, extending successful use of no-till or similar systems to finer textured soils seems advantageous

Sea-level trends along freshwater and seawater mixing in the uruguayan Rio de la Plata estuary and Atlantic Ocean coast

Sea level is rising worldwide with local differences due to global and regional drivers. This article analyses yearly freshwater and sea level trends and fluctuations during the mixing of fresh- and sea-water along the Uruguayan coast of the Rio de la Plata River estuary and the Atlantic coast from 1961 to 2014. The global and regional drivers as well as local co-variables are described, classified in nine discrete classes and inter-correlated. Despite the observed increasing trends, local sea level rises (SLR) are not well correlated with global SLR except at the estuarine-ocean boundary (Punta del Este station). Freshwater inflow, which variability often coincides with Oceanic El Niño-La Niña (ONI-ENSO) events, is the first descriptor of sea level fluctuations and outliers all along the coast, particularly at Punta del Este. Local SLR roughly follows the overall global trend with periods of acceleration and stabilization often coinciding with ENSO event

Soil quality impacts of current South American agricultural practices

Increasing global demand for oil seeds and cereals during the past 50 years has caused an expansion in the cultivated areas and resulted in major soil management and crop production changes throughout Bolivia, Paraguay, Uruguay, Argentina and southern Brazil. Unprecedented adoption of no-tillage as well as improved soil fertility and plant genetics have increased yields, but the use of purchased inputs, monocropping i.e., continuous soybean (Glycine max (L.) Merr.), and marginal land cultivation have also increased. These changes have significantly altered the global food and feed supply role of these countries, but they have also resulted in various levels of soil degradation through wind and water erosion, soil compaction, soil organic matter (SOM) depletion, and nutrient losses. Sustainability is dependent upon local interactions between soil, climate, landscape characteristics, and production systems. This review examines the region’s current soil and crop conditions and summarizes several research studies designed to reduce or prevent soil degradation. Although the region has both environmental and soil resources that can sustain current agricultural production levels, increasing population, greater urbanization, and more available income will continue to increase the pressure on South American croplands. A better understanding of regional soil differences and quantifying potential consequences of current production practices on various soil resources is needed to ensure that scientific, educational, and regulatory programs result in land management recommendations that support intensification of agriculture without additional soil degradation or other unintended environmental consequences.EEA ParanáFil: Wingeyer, Ana Beatriz. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Paraná; ArgentinaFil: Amado, Telmo Jorge Carneiro. Universidade Federal de Santa Maria. Centro de Ciências Rurais; BrasilFil: Pérez Bidegain, Mario. Universidad de la República. Facultad de Agronomía; UruguayFil: Studdert, Guillermo. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Balcarce; ArgentinaFil: Perdomo Varela, Carlos Honorio. Universidad de la República. Facultad de Agronomía; UruguayFil: García, Fernando O. International Plant Nutrition Institute. Americas and Oceania Group. Latin America - Southern Cone; ArgentinaFil: Karlen, Douglas L. United States. Department of Agriculture. Agricultural Research Service; Estados Unido

Tendencias recientes de las precipitaciones e impactos asociados con ENSO en la cuenca del Río de la Plata

La evolución temporal de la precipitación anual sobre la cuenca del Río de la Plata (RdP) durante el periodo 1971-2015, evidencia un incremento aproximado de 40 mm y una alta variabilidad interanual, particularmente influenciada por El Niño. Se destacan los años 2002 y 2014 como los más húmedos, superando los 1.700 mm/año, mientras que 1999 y 2008 se destacan como los años más secos, coincidiendo con fases frías del ENSO. La precipitación anual ha aumentado en el promedio de la cuenca (alrededor de 40 mm más en la actualidad que en la década de 1970). Sin embargo, al norte de la cuenca se observa disminución. El índice de intensidad diaria de precipitación (SDII) ha aumentado, aproximadamente 3 mm respecto a los años setenta. Las fuertes tasas de tendencia positiva de lluvia correspondientes a días húmedos para RR>99 percentil (RR99p) son evidentes en la mayor parte de la cuenca. La fuerte tendencia incremental de la precipitación anual parece estar más relacionada con la intensificación de los eventos extremos. Se sugiere que la cuenca se comporta como más húmeda probablemente asociada a eventos de lluvias extremas, que con una mayor frecuencia de días húmedos. Se registraron varias inundaciones, muchas de ellas asociadas a fase cálida del ENSO, que han impactado en la población, debido en gran medida a la vulnerabilidad asociada a la exposición.The evolution of the annual precipitation over the Rio de la Plata basin (RdP) during the period 1971-2015, shows an approximate increase of 40 mm and a high interannual variability, particularly influenced by El Niño. The years 2002 and 2014 are the most humid, exceeding 1,700 mm / year, while 1999 and 2008 stand out as drier years, coinciding with the cold phase of ENSO. Annual precipitation is increased in the basin average (about 40 mm more at present than in the 1970s). However, to the north of the basin there is a decrease. The daily precipitation intensity index (SDII) has increased, approximately 3 mm from the 1970s. The strong positive rainfall rates corresponding to wet days for RR> 99 percentile (RR99p) are evident in most of the basin. The strong incremental trend of annual precipitation seems to be more related to the intensification of extreme events. It is suggested that the basin behaves as wetter probably associated with events of extreme rains, than with a greater frequency of wet days. There were several floods, many associated with El Niño, which have impacted the population, largely due to the vulnerability associated with exposure

Grid Computing for Climate Processing on South America

O projeto LAG-Clima quer estabelecer um ambiente de computação em grade de processamento e compartilhamento de dados. O objetivo é manter uma rede de interconexão entre instituições na América do Sul para previsão climática em meso-escala e disponibilizar dados. Plataforma de softwares: BRAMS (código meteorológico de meso-escala), OurGri

Climate Risks and Reasons for Concern along the Uruguayan Coast of the Rio de la Plata Estuary

The Uruguayan coast of the Río de la Plata river estuary (RdlP) is 300 km long. It encompasses an inner tidal river and a middle and an outer estuary. The RdlP is a micro-tidal system dominated by river inflow from the Paraná and Uruguay rivers and southern winds with increasingly frequent wind-induced storm surges impacting the coast. The El Niño-Southern Oscillation influences the river inflow, prevailing winds, water/sea level and beach erosion. First, we focus on the IPCC Reasons for Concern (RFC) about the trends of climate risks threatening the Uruguayan coast. The trends and maxima of air temperature, water/sea levels and river inflow in three coastal stations from 1980 to 2019 show temporal changes attributable to climate change and El Niño-Southern Oscillation (ENSO). The occurrence, evolution and Montecarlo simulations of return periods of the yearly river flow and sea level height maxima provide metrics of RFC to categorise the climate risks from past to projected future and the level of risk from undetectable to very high. Then, we summarise some current and expected climate risks and present the current adaptation framework and some expected impacts. The RFC has increased, reaching moderate to high-risk levels

The state of the Martian climate

60°N was +2.0°C, relative to the 1981–2010 average value (Fig. 5.1). This marks a new high for the record. The average annual surface air temperature (SAT) anomaly for 2016 for land stations north of starting in 1900, and is a significant increase over the previous highest value of +1.2°C, which was observed in 2007, 2011, and 2015. Average global annual temperatures also showed record values in 2015 and 2016. Currently, the Arctic is warming at more than twice the rate of lower latitudes

Modeling phosphorus transport using the WEPP model

The Water Erosion Prediction Project (WEPP) model has been widely tested for its ability to predict soil erosion, runoff, and sediment delivery over a very wide range of conditions and scales for both hillslopes and watersheds. However, WEPP has not been used to estimate nutrient loss, in particular phosphorus losses. It is well known that most of the phosphorus transported from cropland is attached to sediment; consequently management practices that reduce erosion and sediment transport could reduce phosphorus losses. Management practices like vegetative filter strips, grass barriers, and multispecies riparian buffers have been proposed to reduce the transport of sediment and nutrients from agricultural lands to streams. However, research has not specifically addressed the question of how different amounts of perennial vegetative cover distributed in the landscape could affect soil loss and water quality. The first objective of this dissertation is to incorporate and test the ability of WEPP to estimate phosphorus loss with sediment at the watershed scale. The second objective is to study the effect of different landscape configurations on sediment yield and phosphorus loss using the WEPP model. The hypothesis related to the first objective is that WEPP can be coupled with a simple algorithm to simulate transport of phosphorus bound to sediment at the watershed outlet. Two hypotheses are related to the second objective. The first hypothesis is that increasing the amount of perennial cover located at the bottom of the hillslope will reduce sediment yield and phosphorus loss within a corn-soybean rotation at the watershed scale. The second hypothesis is that the strategic placement of perennial cover strips distributed in the hillslopes will reduce sediment yield and phosphorus export from the watershed compared to the same proportion of perennial cover located at the bottom of the hillslope. Two watersheds (side by side) in corn-soybean rotation were used to test the model. Watershed sizes were 5.05 and 6.37 ha. Total phosphorus (TP) loss at the watershed outlet were simulated as the product of TP in the soil (kg of TP kg-1 of soil), amount of sediment at the watershed outlet (kg of soil ha-1), and an enrichment ratio (ER) factor. One approach (P-empirical) estimated ER according to an empirical relationship, and the other approach used ER calculated by WEPP (P-WEPP). To address the first hypothesis of the second objective the scenarios were: 2.5% (2.5_B scenario), 5% (5_B scenario), 10% (10_B scenario), 15% (15_B scenario), and 20% (20_B scenario) of the area converted to perennial cover and placed at the bottom of the hillslope. To address the second hypothesis of the second objective the scenarios included 10% of the area in perennial cover placed at the bottom of the hillslope (10_B scenario), 10% in perennial cover with 50% at the bottom of the hillslope and the other 50% placed 40 m upslope (10_S scenario), 10% in perennial cover where WEPP simulated maximum detachment (10_WEPP scenario), and 20% in perennial cover with 50% at the bottom of the hillslope and the other 50% at 40 m upslope (20_S scenario). The same baseline scenario was used to address both hypotheses of the second objective. This scenario corresponded to a corn soybean rotation. The t-test failed to reject the null hypothesis that there was no statistical difference between the mean measured and simulated TP loss. This was the case for both methods (p=0.49 and p =0.40, P-empirical and P-WEPP, respectively). The Nash-Sutcliffe coefficient was 0.80 and 0.78 for the P-empirical and P-WEPP method, respectively. The inclusion of perennial cover at the bottom of the hillslope decreased the amount of sediment delivered to the channel; the reductions modeled for the various scenarios when compared to the baseline scenario were in the range of published field work. However, sediment yield and phosphorus losses at the watershed scale were affected by erosion in the channels. Doubling the amount of perennial cover from 10% to 20% placed at the bottom of the hillslope reduced the amount of sediments and total phosphorus with sediment on average by 34% and 32%, respectively. With 20% perennial cover, sediment yield was reduced on average by 38% and 74% compared to the baseline scenario for the 20_S and 20_B scenarios, respectively. Within WEPP modeling limitations, this work suggested that placement at the bottom may provide the greatest benefit.</p