Mirta Teresinha Petry

Funções de pedotransferência para estimativa da retenção de água em alguns solos do Rio Grande do Sul

Soil physical hydraulic properties are determinations considered expensive and difficult to obtain. The use of pedotransfer functions (PTFs) is an alternative for obtaining such properties more easily and practically costless. The objective of this study was to develop and validate PTFs to estimate soil water retention of different textural soil classes in the State of Rio Grande do Sul, Brazil. The research was carried out using data from physical analysis of soils belonging to the database of Sistema Irriga laboratory, Universidade Federal de Santa Maria. This database consists of soil texture information (sand, silt and clay), density (of soil and of particles), soil porosity (macro, micro and total), besides of water content information at the matrix potential of 0, -1, -6,-33, -100, -500 e -1500kPa. Soil samples were collected on the surface layer of cultivated soils of RS. The variables were submitted to a correlation test, and were subsequently analyzed in multiple regressions test to obtain the PTFs, using the stepwise option of the SAS statistical program. The generated PTFs showed greater associations of soil attributes only related to soil structure such as soil water retention for higher potential (0 and -1kPa) and textural and structural attributes for lower potential (-33, -100, -500 e -1500kPa). The PTFs showed high accuracy in estimating soil water holding capacity of the considered potentials.

População de plantas e espaçamento entre linhas do feijoeiro irrigado. II: rendimento de grãos e componentes do rendimento

The objective of this experiment was to evaluate the effect of different plant populations and row spacing on dry matter accumulation, grain yield and yield components of irrigated drybean. The experiment was conducted during the 1997/98 growing season in the experimental field of the Rural Engineering Department of the Federal University of Santa Maria, Santa Maria - RS, Brayl. The cultivar BR-FEPAGRO 44 - Guapo brilhante, (type II) was submitted to three plant populations (175, 250 and 325 thousand plants ha-1) and three row spacing (35, 50 and 65cm). A factorial completely randomized design was used with four replications. Sprinuer irrigations were appiied when maximum crop evapofranspiration, determined based on class A evaporation pan, indicated na accumulated value of 25mm. Results demonstrated that the different plant populations and row spacing did not affect grain yield and grain weight. However, the number ofseeds per legume and legumes per plant increased as plant population decreased. The reduction in row spacing increased shoot dry matter during grain filling period. The cultivar BR-FEPAGRO 44 - Guapo brilhante presented great plasticity of grain yield components mainly because the reduction in plant population resulted in higher grain yield of individual plants.

População de plantas e espaçamento entre linhas do feijoeiro irrigado. I: comportamento morfológico das plantas

Engenheiro Agronomo, Programa de Mestrado em Engenharia Agricola, UFSM.RESUMOO experimento foi conduzido com o objetivo deavaliar variacoes no indice de area foliar, altura das plantas,numero de nos, comprimento dos entrenos na haste principal ealtura das vagens em relacao a superficie do solo do feijoeiroirrigado e cultivado em diferentes populacoes de plantas eespacamentos entre linhas de cultivo. O experimento foiconduzido no ano agricola 1997/98, em area experimental doDepartamento de Engenharia Rural da Universidade Federal deSanta Maria, Santa Maria, RS. A cultivar de feijao preto BR-FEPAGRO 44 - Guapo brilhante, de crescimento indeterminado(tipo II), foi cultivada em tres populacoes de plantas (175, 250 e325 mil plantas ha

Qualidade física de solos irrigados do Estado do Rio Grande do Sul

As areas irrigadas caracterizam-se pela intensificacao dos cultivos e, por consequencia, por uma intensa utilizacao do solo. Isso resulta em uma maior pressao de degradacao da estrutura do solo, ocasionando muitas vezes a compactacao dos solos. O objetivo deste trabalho foi realizar a caracterizacao fisica dos solos irrigados de algumas regioes do Estado do Rio Grande do Sul, com vistas a promover uma base de informacoes para orientar a tomada de decisoes relativas ao manejo de areas irrigadas. Os perfis dos solos foram divididos em tres camadas: (superficial, intermediaria e inferior), nas quais determinaram-se a textura do solo, a densidade do solo (Ds) e de particulas e porosidade. Os solos foram agrupados em faixas de teor de argila, sendo que, para cada faixa de teor de argila, estabeleceu-se um valor critico de densidade do solo (Ds) e de macroporosidade (Macro). As amostras com valores DS maiores que o valor citrico e com valores de macro menores que o valor citrico foram caracterizados com indicacao de compactacao. As amostras de solo coletadas foram classificadas, com maior frequencia na faixa de 400-500g kg-1 de argila, nas camadas superficial e intermediaria e na faixa de argila superior a 700g kg-1 na camada inferior. Do total das areas amostradas, 66,5% apresentaram indicacao de compactacao do solo na camada superficial, 20,5% na camada intermediaria e 9,5% na camada inferior.

Physical quality of irrigated soils in some regions of Central Brazil.

Intensive soil cultivation using heavy machinery, especially when soil moisture content is relatively high, has caused degradation of the physical properties of soil, mainly soil compaction. The objective of this study was to evaluate the physical quality of soil of some irrigated regions of Brazil and to collect information necessary to guide soil management decisions. This study was carried out in areas irrigated by center pivots in the States of Goias, Minas Gerais and Sao Paulo. The soil profile was divided into three soil layers: superficial, intermediate and inferior. The following determinations were conducted: soil texture, bulk density, particle density and soil porosity. Soil types were grouped according to clay content. For each group of clay content, critical values of bulk density and soil macroporosity were established above which (bulk density) and below which (macroporosity) the soil sample were characterized as compacted. Considering the entire area sampled in the superficial layer, 14.2% of the samples collected in Goias, 9.5% of soil samples collected in Minas Gerais and 34% of the samples collected in Sao Paulo presented indications of soil compaction as a function of bulk density and macroporosity.

The Use of a Meteorological Station Network to Provide Crop Water Requirement Information for Irrigation Management

Despite of the water use increment for other sectors than agriculture, the water use for irrigation is the main water consumer in global scale. However, irrigation has been pressured by the civil society to improve water use efficiency in agriculture, to prevent water scarcity for human population that grows continuously, mainly in developing areas of the planet. On the other hand, the irrigation practice is considered the main tool to increase water use efficiency, either for increasing crop production or for keeping rural works in the agricultural areas. The water use efficiency can be improved through the adoption of an efficient irrigation management and programming that results in water conservation. Several methods of irrigation management have been developed and used in the last few decades, but the adoption of the majority of then by the irrigated grower was limited by the cost, time of installation, maintenance and local difficulties that the selection of a specific method involves. In arid regions, the decision of “when” and “how much” to irrigate is relatively simple. However, in wet regions when complementary irrigation is used, the irrigation scheduling is a complex task, mainly due to the water added from rainfall events. The Sistema Irriga™ is basically a service of irrigation management developed by the Federal University of Santa Maria, Brazil. The criteria used by this method to decide the amount of each irrigation application is based on crop parameters of the irrigated crop, soil physical characteristics, meteorological conditions and characteristics of the irrigation system and irrigation method, combined with a mathematical model to determine the reference and crop evapotranspiration. This paper describes all factors and parameters used by the Sistema Irriga™ service, since the data acquisition (plant, soil, weather and irrigation system information), data processing and how the irrigation recommendation is available to the farmers.

Disponibilidade de água do solo ao milho cultivado sob sistemas de semeadura direta e preparo convencional

The aim objective of this study was to quantify the soil water storage, plant-available water and extraction of soil water by corn plants under irrigation and terminal drought. Plants were cultivated under no-tillage and conventional tillage systems. Two experiments were conducted in the 1999/00 and 2000/01 growing season on an experimental field of the Agricultural Engineering Department of the Federal University of Santa Maria. Treatments consisted of a 2 x 2 factorial scheme, in a completely randomized design, with four replications. The tested treatments were: Factor A - irrigation management (irrigation and terminal drought, 27 days after emergence, when plants presented seven fully expanded leaves) and; Factor B - tillage system (no-tillage and conventional tillage). Irrigation water was applied to raise the soil water content to the maximum limit of plant-available water, always when the cumulative maximum crop evapotranspiration reached a value of 25 mm. Soil water content was measured three times a week to determine soil water extraction and water availability for corn plants. Results indicated a similar amount of water available to corn plants cultivated in both tillage systems during the two growing seasons. Conventionally cultivated maize plants extracted a higher amount of soil water than plants cultivated in no-tillage system.

Rendimento de grãos de soja em função de sistemas de plantio e irrigação por superfície em Planossolos

The objective of this work was to evaluate the effect of planting systems and supplementary border irrigation on soybean yield in areas of a compacted layer in the soil subsurface. Two experiments were carried out in a randomized complete block design, in a factorial arrangement, with four replicates, in the state of Rio Grande do Sul, Brazil. Experiment 1 was performed in Santa Maria, in the 2013/2014 and 2014/2015 growing seasons; and experiment 2 in Formigueiro, in the 2013/2014 crop season. The treatments consisted of factors A and D. Factor A considered the following planting systems: A1, sowing using double disks; A2, sowing using notched disks; A3, sowing using shanks; A4, sowing using shanks and soil accommodation mechanism; A5, raised bed system; and A6, deep tillage and sowing using double disks. Factor D consisted of irrigated or nonirrigated treatments. In the 2014/2015 growing season, factor A4 was changed using a shank at 5 cm from the seeding line. Experiment 2 consisted only of factor A of experiment 1, without the raised bed system. The systems with deep tillage and sowing using a shank provide higher soybean grain yield. Irrigation at soil moisture conditions lower than 60% of field capacity increases soybean grain yield.

SOIL TEXTURE CLASSES AND METEOROLOGICAL CONDITIONS AFFECTING PLANT AVAILABLE WATER TO SORGHUM AND SOYBEAN

The objective of this work was to identify differences in soil water availability and plant available water, and morphological changes of sorghum and soybean crops submitted to irrigation and terminal soil water deficit in three soil texture classes. Two experiments were conducted in the experimental field of the Rural Engineering Department of the Federal University of Santa Maria-RS, during 1997/98 (sorghum) and 1998/99 (soybean) growing seasons. A set of drainage lisymeters was used. A rain shelter was used to avoid rainfall on the experiment site. A completely randomized statistical design with two replications was used. Treatments applied were two water management and three soil texture classes. Irrigations were applied when cumulative maximum crop evapotranspiration reached 25mm; the terminal soil water deficit for sorghum and soybean plants was imposed during V3 and V8 vegetative growth, respectively. The three soil texture classes used were clayey, silty clay loam and sandy loam. Upper limit and lower limit of plant availability water to plants were evaluated in the lysimeters. Field capacity and permanent wilting point were used to determine soil water availability, using the conventional methodology. Results indicated that the soil water availability was 44, 66, and 72 mm for the clayey, silty clay loam and sandy loam soil classes, respectively. However, the plant available water to sorghum and soybean plants, average of two years, was 95, 154 and 124 mm. Values of plant available water were 109, 133 and 72% higher than soil water availability determined by conventional methodology. Reduction in leaf area index, plant height and number of nodes in sorghum and soybean plants submitted to terminal soil water deficit was more expressive in the clayey soil, compared with irrigated plants. These results clearly indicated that plant available water needs to be determined in the field, for each soil classes, soil management and crop species.

Estimation of Basal Crop Coefficient Using Remotely Sensed Vegetation Indices for Center Pivot Irrigated Maize in Southern Brazil

The partitioning between basal crop coefficient (Kcb) and soil evaporation coefficient (Ke) of the crop coefficient (Kc) during the crop cycle is lately been used to develop a more reliable and precise irrigation management. A currently approach under development is estimating Kcb using vegetation indices, obtained from remote sensors. This approach allows an alternative and independent procedure in comparison with the classical methodological approach described in FAO 56 or models that simulate the soil water balance using land information; one model that uses this approach is SIMDualKc. This estimation could also be done using surface energy balance models, however, these models present greater complexity and greater number of input data than the conventional Kc-ETo approach. The objective of this study was to determine the initial, mid-season and lateseason basal crop coefficients (Kcb ini, Kcb mid, Kcb end) using historical records of the red and near infrared reflectance of central pivots, to calculate the normalized vegetation index (IV), adjusted for the entire maize growth, in conjunction with soil field and phenology data of seven center pivot fields in Southern Brazil. Eight Landsat5/TM satellite images of 222 and 223 orbits in point 80, and information from these seven maize monitoring fields during 2004/2005 growing season were used. Crop height and crop growth stages, as well as meteorological weather data collected from a weather station installed in the area were used. A density coefficient (Kd) determined using the fraction of vegetation ground cover (fc) was used for the Kcb estimation through VI, incorporating the impact of both the vegetation density and the plant height. The estimated values were: Kcb ini = 0.20 ± 0.09, Kcb mid = 0.20 ± 0.95 and Kcb end 0.52 ± 0.22, considering 95% of probability. The results showed good agreement with Kcb values obtained using SIMDualKc model in a previous study of this research group for the southern region of Brazil, which were Kcb ini = 0.20, Kcb mid = 1.12 and Kcb end = 0.80.