ABSTRACT The use of crop modeling can be useful to understand the interactions between the soil-plant-atmosphere system. The objective of this study was to evaluate sensitivity analysis of the AquaCrop model parameters for wheat crop in the Campos Gerais Region. The varietie tested was TBIO Sinuelo in Castro, Ponta Grossa and Itaberá cities. The analyzed parameters refer to crop phenology, transpiration, biomass production, yield formation, stresses and soil management. The sensitivity analysis was realized varying individually each input parameter in the AquaCrop for the calculation of the Relative Sensitivity Index (SI). The most sensitive parameters of the AquaCrop were: reference harvest index (HIo); water productivity normalized for evapotranspiration and CO2 concentration (WP*); crop coefficient when canopy expansion is complete (KcTR,x); fertility levels; and maximum canopy cover (CCx). The higher sensitivity of HIo and WP* is because they are directly related to two main equations of AquaCrop, linked to the estimates of dry above-ground biomass and yield formation, respectively. The AquaCrop counts WP* reflecting directly on dry above-ground biomass production and on final grain yield. The canopy decline coefficient (CDC) presented considerable sensitivity only in Castro due to the longer duration of the phenological cycle. Fertility levels and saturated hydraulic conductivity (Ksat) in Castro was the least sensitive parameters in the analysis.

RESUMEN Los sistemas agrícolas pueden alterar las propiedades física e hidráulicas del suelo y, en consecuencia, su calidad. Nuestro objetivo fue determinar y asociar las propiedades física e hidráulicas de cuatro tipos de suelo bajo un sistema de siembra directa sobre rastrojo, localizados en la región subtropical de Brasil, así como crear un conjunto de datos disponibles que pueden ser utilizados en estudios posteriores. Fueron recolectadas muestras de suelo alteradas y inalteradas en tres camadas: 0,0 - 0,10 m; 0,10 - 0,25 m; y 0,25 - 0,40 m en seis localidades de los estados de Paraná y São Paulo. Fueron determinados la textura del suelo, la densidad aparente y de las partículas del suelo, la porosidad (total, macro y micro), la humedad volumétrica del suelo (punto de marchitez permanente y capacidad de campo), la capacidad de agua disponible y la conductividad hidráulica saturada. El promedio de la densidad aparente del suelo está dentro de limites considerados óptimos (1000 kg m(3 y 1400 kg m(3) de acuerdo con las clases texturales del suelo. El promedio de la porosidad total según los suelos estudiados (entre 0.47 m3 m-3 y 0.63 m3 m-3) se mantuvo próxima a la condición ideal para el desarrollo anual de la cultura en sistema de siembra directa sobre rastrojo. La proporción entre micro y macroporos fue de aproximadamente 2:1. El promedio de la capacidad del agua disponible del suelo ha variado entre 48 mm y 60 mm. La conductividad hidráulica saturada promedio fue clasificada como “moderada”. El manejo adoptado por más de 20 años en las áreas estudiadas no presentó alteración en las once propiedades físicas e hidráulicas del suelo, al compararlo con los límites normales establecidos en la literatura.

ABSTRACT Agricultural systems can alter the soil physical and hydraulic properties, and consequently its quality. We aimed to determine and associate the physical and hydraulic properties of four soil types under no-tillage system in the Subtropical region of Brazil, as well as to create a data set available to be explored by further studies. Disturbed and undisturbed soil samples were collected from three layers: 0.0 - 0.10 m; 0.10 - 0.25 m; and 0.25 - 0.40 m at six localities in the Paraná and São Paulo States. Soil texture, soil bulk density and particle density, porosity (total, macro and micro), volumetric water content (permanent wilting point and field capacity), available water capacity and saturated hydraulic conductivity were determined. The average soil bulk density was within 1000 kg m(3 to 1400 kg m(3, which is considered optimum for the respective soil textures. The average total porosity (between 0.47 m3 m-3 and 0.63 m3 m-3) was close to an optimal condition for annual crop development under no-tillage system. The proportion between micro and macropores was approximately 2:1. The average values of soil available water capacity ranged from 48 mm to 60 mm. The average for the saturated hydraulic conductivity was classified as “moderate”. The management adopted for more than 20 years in the studied areas did not bring about critical values for the eleven physical and hydraulic soil properties examined, when compared to acceptable ranges verified in literature.

Resumo: O objetivo deste trabalho foi avaliar o efeito do atraso da colheita sobre umidade dos grãos, massa de mil grãos e produtividade da soja, assim como identificar as variáveis agrometeorológicas mais importantes durante o período pré-colheita e propor algoritmos empíricos para a estimativa das perdas de produtividade. Os experimentos foram realizados em Castro, PR, e Itaberá, SP, nas safras de 2011/2012 a 2013/2014, da cultivar de soja 'NA5909RG', em sete ambientes. Os tratamentos consistiram de oito momentos de colheita de soja a partir do estádio fenológico R8.2. A análise de grupos de experimentos mostrou interação significativa entre ambientes e momentos de colheita. A umidade e a produção de grãos são influenciadas diretamente pelo número de dias com precipitação pluvial igual ou superior a 3 mm. No estádio fenológico R8.2, são obtidos os maiores valores de produtividade; no entanto, após esse estádio, há declínio da produtividade em consequência do atraso da colheita. As maiores perdas acumuladas de produtividade ocorrem em ambientes com alta frequência de precipitações pluviais e com temperatura e radiação solar global elevadas. Dois algoritmos com base em variáveis agrometeorológicas são propostos para a estimativa da perda de produtividade de soja.

Abstract: The objective of this work was to evaluate the effect of harvest delay on grain moisture, thousand grain weight, and soybean productivity, as well as to identify the most important meteorological variables during pre-harvest and to propose empirical algorithms to estimate soybean yield losses. The experiments were carried out in the municipalities of Castro, in the state of Paraná, and of Itaberá, in the state of São Paulo, Brazil, in the seasons from 2011/2012 to 2013/2014, with the soybean cultivar 'NA5909RG', in seven environments. Treatments consisted of eight harvest times of soybean after phenological stage R8.2. The analysis of group of experiments showed a significant interaction between environments and harvest times. Grain moisture and grain yield are directly affected by the number of days with rainfall equal to or higher than 3 mm. At the R8.2 phenological stage, the highest values of productivity are obtained; however, after this stage, there is a decline of productivity as a consequence of harvest delay. The greatest, accumulated losses of productivity occur in environments with high frequency of rainfall, and high temperature and solar radiation. Two algorithms based on agrometeorological variables are proposed to estimate soybean yield loss.