Kleber Trabaquini

Analysis of agricultural intensification in a basin with remote sensing data

The last few decades have been marked by important changes in the Brazilian agriculture, especially with respect to crop-management practices. This study aimed to analyze the dynamics of cropping systems in a typical agricultural river basin in the state of Mato Grosso. Landsat satellite images and time series of Moderate Resolution Imaging Spectroradiometer vegetation index profiles were analyzed from 2000 to 2010. First, we assessed the horizontal expansion that occurred in the agricultural areas. Subsequently, using the product MOD13Q1, some metrics were established to identify the vertical intensification of soil use (single- or double-cropping systems). Results showed stagnation in the expansion of new deforested areas for agriculture in the 2003/2004 growing season, with simultaneous vertical intensification of agriculture. The adoption of the double-cropping system (e.g., soybean/corn and soybean/cotton) expanded by 266% during the studied period and reached 56% of the croplands in the 2009/2010 growing season.

Cloud Cover Assessment for Operational Crop Monitoring Systems in Tropical Areas

The potential of optical remote sensing data to identify, map and monitor croplands is well recognized. However, clouds strongly limit the usefulness of optical imagery for these applications. This paper aims at assessing cloud cover conditions over four states in the tropical and sub-tropical Center-South region of Brazil to guide the development of an appropriate agricultural monitoring system based on Landsat-like imagery. Cloudiness was assessed during overlapping four months periods to match the typical length of crop cycles in the study area. The percentage of clear sky occurrence was computed from the 1 km resolution MODIS Cloud Mask product (MOD35) considering 14 years of data between July 2000 and June 2014. Results showed high seasonality of cloud occurrence within the crop year with strong variations across the study area. The maximum seasonality was observed for the two states in the northern part of the study area (i.e., the ones closer to the Equator line), which also presented the lowest averaged values (15%) of clear sky occurrence during the main (summer) cropping period (November to February). In these locations, optical data faces severe constraints for mapping summer crops. On the other hand, relatively favorable conditions were found in the southern part of the study region. In the South, clear sky values of around 45% were found and no significant clear sky seasonality was observed. Results underpin the challenges to implement an operational crop monitoring system based solely on optical remote sensing imagery in tropical and sub-tropical regions, in particular if short-cycle crops have to be monitored during the cloudy summer months. To cope with cloudiness issues, we recommend the use of new systems with higher repetition rates such as Sentinel-2. For local studies, Unmanned Aircraft Vehicles (UAVs) might be used to augment the observing capability. Multi-sensor approaches combining optical and microwave data can be another option. In cases where wall-to-wall maps are not mandatory, statistical sampling approaches might also be a suitable alternative for obtaining useful crop area information.

Estimates of land use and land cover change and soil loss in the Brazilian Cerrado through geotechnology

The Cerrado biome, with approximately 206 million hectares of Brazilian territory, is undergoing significant changes in recent decades due to land use and land cover changes. The agricultural activities are identified as the main sources of rapid reduction of native vegetation in the Cerrado in the last decade. The objective of this study is to evaluate changes in land cover that occurred in recent decades in a watershed located in the state of Mato Grosso, Cerrado biome, and therefore assess the soil loss from erosion, using the USLE model. Results showed that 15% of the area had already been converted into agriculture in 1980. Results for the years of 1990, 2000 and 2010 were 37%, 51% and 61%, respectively. The soil loss rates estimated from the USLE model showed that the average annual soil loss increased significantly with time.

Assessment of suitable observation conditions for a monthly operational remote sensing based crop monitoring system

Cloud cover is the main issue to consider when remote sensing images are used to identify, map and monitor croplands, especially over the summer season (October to March in Brazi). This paper aims at evaluating clear sky conditions over four Brazilian states (São Paulo, Paraná, Santa Catarina, and Rio Grande do Sul) to assess suitable observation conditions for a monthly basis operational crop monitoring system. Cloudiness was analyzed using MODIS Cloud Mask product (MOD35), which presents four labels for cloud cover status: cloudy, uncertainty, probably clear and confident clear. R software was used to compute average values of clear sky with a confidence interval of 95% for each month between July 1st, 2000 and June 30th, 2013. Results showed significant differences within and between the four tested states. Moreover, the period from November to March presented 50% less clear sky areas when compared to April to October.

Land use intensity assessed through geotechnology in Brazilian savannah and the effects on soil nutrient

Soils from central Brazil have been intensively used over the last decades due to the rapid conversion of savannah (Cerrado) into corn/soybean fields. This study have the aim to study modifications in the chemical properties (total carbon and total nitrogen ) of soils in the Rio Verde watershed as a function of the land use time for agriculture, as determined from Landsat satellite images. The largest values of total carbon and total nitrogen are found in soils under savannah, showing significant differences from the rest of classes of use time. A loss of up to 29 % of total nitrogen and 38% of total carbon was recorded when natural forest (savannah) soil was converted to agricultural land.