José Paulo Molin

ESTABLISHING MANAGEMENT ZONES USING SOIL ELECTRICAL CONDUCTIVITY AND OTHER SOIL PROPERTIES BY THE FUZZY CLUSTERING TECHNIQUE

The design of site-specific management zones that can successfully define uniform regions of soil fertility attributes that are of importance to crop growth is one of the most challenging steps in precision agriculture. One important method of so proceeding is based solely on crop yield stability using information from yield maps; however, it is possible to accomplish this using soil information. In this study the soil was sampled for electrical conductivity and eleven other soil properties, aiming to define uniform site-specific management zones in relation to these variables. Principal component analysis was used to group variables and fuzzy logic classification was used for clustering the transformed variables. The importance of electrical conductivity in this process was evaluated based on its correlation with soil fertility and physical attributes. The results confirmed the utility of electrical conductivity in the definition of management zones and the feasibility of the proposed method.

Adoption and use of precision agriculture technologies in the sugarcane industry of Sao Paulo state, Brazil

Precision agriculture (PA) technologies are being applied to crops in Brazil, which are important to ensure Brazil’s position in agricultural production. However, there are no studies available at present to indicate the extent to which PA technologies are being used in the country. Therefore, the main objective of this research was to investigate how the sugar-ethanol industry in São Paulo state, which produces 60% of the domestic sugarcane, is adopting and using these techniques. For this purpose, primary data were used, which were obtained from a questionnaire sent to all companies operating in the sugar-ethanol industry in the region. The aim was to determine to what extent these companies are adopting and using PA technologies, and also to promote a more in-depth discussion of the topic within the sugar-ethanol industry. Information was obtained on the features of the companies, on sources of information that they use for adopting these technologies, on their impacts on these companies and on obstacles hindering their adoption. The main conclusions of this research suggest that companies that adopt and use PA practices reap benefits, such as managerial improvements, higher yields, lower costs, minimization of environmental impacts and improvements in sugarcane quality.

Comportamento do NDVI obtido por sensor ótico ativo em cereais

The objective of this work was to evaluate the behavior of the normalized difference vegetation index (NDVI), with an active optical sensor, in wheat, triticale, barley and corn crops. Experiments were conducted in Parana and Sao Paulo, comparing different soil classes, N rates and sources, and wheat varieties. The following variables were determined: NDVI, N foliar content, dry mass and crop yield. Regression analyses were performed between NDVI and applied N rates, N foliar content, dry mass and yield. Correlation analyses among the variables were performed. Wheat, triticale and barley crops showed response to increasing N rates by the increase in the NDVI readings, to N foliar content and to yield. Measured by the used active optical sensor the NDVI shows high potential for N management wheat, triticale and barley crops, and low potential for corn crops. There is interference of wheat varieties in the active optical sensors readings.

Utilização de sensor óptico ativo para detectar deficiência foliar de nitrogênio em algodoeiro

Visou-se com este trabalho, avaliar, em condicoes de campo, o efeito da variacao de doses de nitrogenio na deteccao do teor de nitrogenio foliar do algodoeiro (Gossypium hirsutum L. var. latifolium Hutch), utilizando-se propriedades de reflectância obtidas por um sensor optico ativo. O delineamento experimental foi o aleatorizado em blocos, com cinco tratamentos (0, 50, 100, 150 e 200 kg ha-1 de N) e quatro repeticoes. Os dados do Indice de Vegetacao Diferenca Normalizada (NDVI) e da razao simples vermelho/infravermelho proximo (V/IVP) foram coletados no periodo de 23 a 92 dias apos a emergencia (DAE) totalizando nove datas de coleta; coletaram-se tambem dados referentes ao indice de clorofila, indice de area foliar (IAF) e altura de plantas. Os valores do NDVI apresentaram tendencia crescente ao longo do periodo das leituras, enquanto a relacao V/IVP teve comportamento inverso e, a partir de 45 DAE, foram afetados significativamente pelas doses de N aplicadas. Relacoes significativas foram observadas entre os valores do NDVI, indice de clorofila e IAF; aos 92 DAE o NDVI apresentou relacao linear positiva e altamente significativa com o teor foliar de N. O sensor utilizado pode ser uma ferramenta efetiva para estimar a deficiencia foliar de nitrogenio em algodoeiro.

Remoção de erros em mapas de produtividade via filtragem de dados brutos

As yield data are collected automatically it allows for errors to be introduced into the data collected. Filtering processes might be able to eliminate part of the errors and improve the quality of yield data. The development of a filtering process may be set up based on the individual characteristics of each error. These errors may be related to incorrect position, too high or too low yield, swath width, grain moisture, null distance between points, filling interval and outliers. The filtering algorithm was implemented on six sets of data generated from six different commercial yield monitors. A geostatistical analysis of the data sets showed that the application of the filtering process decreased the nugget effect and improved the cross validation quality index.

Comparison of crop canopy reflectance sensors used to identify sugarcane biomass and nitrogen status

Canopy reflectance sensors are useful tools for guiding nitrogen fertilization in crops. However, studies of sugarcane comparing the efficiency of different devices for determining crop parameters are scarce. The objective of this study was to compare the performance of canopy sensors in detecting sugarcane variability. Four nitrogen (N) rate experiments were conducted (plots), along with biomass sampling, chlorophyll meter readings and leaf N concentration determination in another four fields by canopy sensor readings guided samplings. The examined canopy sensors were GreenSeeker and two Crop Circle models (ACS-210 and ACS-430), which allowed the calculation of different normalized difference vegetation index (NDVI) configurations. Neither of the canopy sensors showed a correlation with the obtained chlorophyll meter readings (SPAD) or leaf N content within the fields, while high correlations with above-ground biomass were found, indicating that the plant population and vigor interfered with the canopy sensor readings. The devices showed similar suitability in terms of N rate differentiation and correlations with crop parameters. However, the NDVI calculated from the Crop Circle ACS-430 sensor using a red-edge waveband (NDRE) showed the best results, displaying the greatest range of measured values and the highest sensitivity as a biomass predictor. Regardless of the canopy sensor and wavebands used, all of the analyzed sensors proved to be good tools for identifying the variability of crop development in sugarcane fields.

Spatial and temporal variability of soil electrical conductivity related to soil moisture

Soil electrical conductivity (ECa) is a soil quality indicator associated to attributes interesting to site-specific soil management such as soil moisture and texture. Soil ECa provides information that helps guide soil management decisions, so we performed spatial evaluation of soil moisture in two experimental fields in two consecutive years and modeled its influence on soil ECa. Soil ECa, moisture and clay content were evaluated by statistical, geostatistical and regression analyses. Semivariogram models, adjusted for soil moisture, had strong spatial dependence, but the relationship between soil moisture and soil ECa was obtained only in one of the experimental fields, where soil moisture and clay content range was higher. In this same field, coefficients of determinations between soil moisture and clay content were above 0.70. In the second field, the low soil moisture and clay content range explain the absence of a relationship between soil ECa and soil moisture. Data repetition over the years, suggested that ECa is a qualitative indicator in areas with high spatial variability in soil texture.

Spatial variability of soil fertility and its relationship with seed physiological potential in a soybean production area

The correlation of soil fertility x seed physiological potential is very important in the area of seed technology but results published with that theme are contradictory. For this reason, this study to evaluate the correlations between soil chemical properties and physiological potential of soybean seeds. On georeferenced points, both soil and seeds were sampled for analysis of soil fertility and seed physiological potential. Data were assessed by the following analyses: descriptive statistics; Pearsons linear correlation; and geostatistics. The adjusted parameters of the semivariograms were used to produce maps of spatial distribution for each variable. Organic matter content, Mn and Cu showed significant effects on seed germination. Most variables studied presented moderate to high spatial dependence. Germination and accelerated aging of seeds, and P, Ca, Mg, Mn, Cu and Zn showed a better fit to spherical semivariogram: organic matter, pH and K had a better fit to Gaussian model; and V% and Fe showed a better fit to the linear model. The values for range of spatial dependence varied from 89.9 m for P until 651.4 m for Fe. These values should be considered when new samples are collected for assessing soil fertility in this production area.

Capacidade de um sensor ótico em quantificar a resposta da cana-de-açúcar a doses de nitrogênio

Techniques of precision agriculture are alternatives to optimize the use of inputs, among them nitrogen. The present work had as its objective to verify the possibility of use of a commercial optical sensor in sugarcane, verifying its capability in identification of the crop response to different nitrogen (N) rates. An experiment was installed in randomized blocks in an experimental area with third sugarcane ratoon, harvested mechanically, with different N rates (0, 50, 100, 150 and 200 kg ha-1) and four repetitions. At 30, 60 and 90 days after the harvest (DAH) the measuring of NDVI (normalized difference vegetation index) was accomplished starting from the optical sensor. No response was verified of NDVI on measurements at the 30 and 60 DAH, however at 90 DAH the sensor was capable to differentiate the doses of applied N, positively correlated with the sugarcane final production. This work gives subsidies to studies of same nature that seek the management of the nitrogen fertilization in sugarcane using optical sensor.

Estudos sobre a mensuração da condutividade elétrica do solo

The electric conductivity is the capacity of a material in driving electric current and one of its usefulness in the agriculture comes from the fact that the soil electrical conductivity (EC) varies with its intrinsic physicochemical variability. The objective of this work was to study the EC behavior and advance on the factors understanding that affects its variability, and develops systems for measuring and mapping EC. We built a system with several measurement configurations, and on the field tests the results were partially satisfactory. In a detailed study using only a commercial EC measuring equipment the results clearly indicated that EC relates with soil texture and moisture, and may represent an important and low price tool for collecting data and characterizing soil physical properties.