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Copyright of Revista Brasileira de Engenharia Agricola e Ambiental - Agriambi is the property of Revista Brasileira de Engenharia Agricola e Ambiental and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Revista Brasileira de Engenharia Agricola e Ambiental - Agriambi is the property of Revista Brasileira de Engenharia Agricola e Ambiental and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Knowledge about soil moisture is essential to maximize irrigation efficiency because it allows the application of water in the proper quantity and at the proper time, thus improving water management. The objective of this study was to evaluate water storage in the soil profile when using a subsurface drip irrigation system at two emitter installation depths (0.20 or 0.40 m) and two water qualities (treated sewage effluent (TSE) and freshwater) in two crop cycles of sugarcane ( Saccharum officinarum L.) in Campinas—SP (Brazil). The experiment was conducted in the experimental area of FEAGRI-UNICAMP, Campinas—SP, Brazil, adopting a randomized block design (RBD) in a factorial 2 × 2 + 1 with 3 replications. The factors studied included the installation of dripper tube at two depths (0.2 and 0.4 m) and two qualities of water (TSE and freshwater) plus a non-irrigation control. The TDR (time domain reflectometry) technique was used to evaluate the moisture in the soil profile by installing five probes with rods at 0.2 m up to 1.0 m depth. Replacement of the calibration equation provided by the TDR reduced the water depth between the first ratoon and the sugarcane plant and reduced the excess humidity from 0.029 and 0.045 cm 3 to 0.002 and 0.007 cm 3 when the drippers were installed at 0.2 m depth (T2 and T4). The installation of a 0.2 m drip tube proved to be an ideal solution for both environmental management and water use efficiency when using treated sewage effluent. No effect on the water distribution in the soil was observed when comparing the water qualities. For management of subsurface drip irrigation by the water balance in the soil, different layers in the soil profile should be considered to calculate the water depth, using the depth of the drip tube installation as a reference. [ABSTRACT FROM AUTHOR]

The use of wastewater in agriculture is an alternative to provide water and nutrients for plants. However, root system development can be affected by water quality and depth of wastewater applied. The objective of this study was to evaluate the sugarcane root system growth using a minirhizotron in a field irrigated with treated sewage effluent and freshwater by subsurface drip irrigation. The treatments tested were two drip line installation depths (0.2 and 0.4 m); two water sources (treated sewage effluent and freshwater) and non-irrigated plots as control. The experiment was a randomized block design with a 2x2 + 1 factorial, with three replications. The root system evaluation (root length and spatial distribution) was performed using a minirhizotron with an access tube buried in the soil profile and installed on a 45 degree angle. The soil moisture was determined using the time-domain reflectometry technique. The lowest moisture on the soil surface resulted in the highest root length density (0.18 cm cm-2) at the non-irrigated plots (p>0.05). The application of treated sewage effluent and the installation depth of drip line did not change the root length of sugarcane in first ratoon (p>0.05). Eighty percent of the root system was accumulated from the soil surface to 0.45 m. [ABSTRACT FROM AUTHOR]

Methodologies based on earth observation remote sensing allow for a precise estimation of actual water requirements for irrigated crops across large areas. In spite of the many number of experiments using or analyzing the relationship between the basal crop coefficient (K cb ) and the soil adjusted vegetation index (SAVI) for maize, the development of new maize hybrid varieties with modifications related to canopy architecture suggest a possible change of the leaf area index (LAI) for maximum K cb and its relationship with the SAVI or other vegetation indices. In addition, we noted a lack of analysis of these relationships for cultivated soybean. The objective of this paper is to analyze the K cb , SAVI and LAI relationships in maize and soybean based on the non-linear relationships proposed by Choudhury et al. (1994). In addition, we propose a modification of the Choudhury et al. (1994) approach based on field-based experimental evidence of a minimum K cb greater than 0. For sites with limited field data, we also analyze the utility of a simple linear regression based on the K cb and SAVI values for bare soil and maximum K cb values. The resulting K cb -SAVI relationships are assimilated into a remote sensing based soil water balance model. The results of the model are analyzed in terms of irrigation requirements and crop evapotranspiration (ETa) for 11 growing seasons in two fields cultivated with irrigated and rain-fed maize and soybean in eastern Nebraska. Comparisons of measured and modelled ETa values indicate a good agreement, with RMSE lower than 0.7 mm d −1 for weekly averaged values. The comparison of actual irrigation applied and irrigation requirements indicate the central pivot systems could not supply adequate water in some growing seasons with higher demands. [ABSTRACT FROM AUTHOR]