Variabilidade espacial de atributos fisico-hidricos do solo cultivado com feijão irrigado sumetido a diferentes sistemas de preparo / Soil physical-hydric attributes spatial variability doe diferent irrigated bean tillage systems

AUTOR(ES)
DATA DE PUBLICAÇÃO

2007

RESUMO

Since last decades irrigation practices are recognized as major water consumers, requiring specific agricultural producers education and awareness on water use and supply. Recent research reports indicate significant water economy, crop yielding as well as contribution to sustainable agricultural development, if direct seedling, when compared with conventional practices, is associated to adequate irrigation management. However, depending on weather conditions as well as on the direct seedling implementation conditions, many crop plantations showed increasing soil bulk density and compaction with increasing soil mechanical resistance to penetration, causing crop production reduction. Based on what it has been exposed before, the objective of this research is to evaluate crop yielding and soil physical-hydric attributes spatial dependence as related to irrigated bean grain production associated to no-tillage and to conventional tillage systems. The Time Domain Reflectometry (TDR) efficiency in the soil moisture monitoring in the same crop systems was also evaluated. Four experimental plots with dimensions of 20m x 30m were seeded with beans in the years and 2005 and 2006 and carried under irrigated and non irrigated conventional as well as no-tillage systems. Each plot was screened with 3m x 3m sampling grids, completing a total of 60 sampling points in each plot. Plot soil was classified as Typical Distroferric Red Latossol. TDR probes were introduced into the soil on each plot to monitor moisture content, also being measured saturated hydraulic conductivity, resistance to penetration and sampling for soil bulk density determination. Elevation of each sampling point was determined by means of an optical instrument and expressed in meters. Spatial dependence analysis was evaluated through geostatistic techniques and the semivariograms parameters were employed to generate isoline maps trough the punctual kriging interpolator of the Surfer 8.0 program. Obtained results indicated TDR calibration as proposed by Topp et al. (1980), considered of universal feature, is not adequate to the soil under study. TDR technique showed to be efficient in monitoring soil moisture content throughout bean plant cycle, being applicable in the irrigation process, since a previous equipment calibration in accordance with soil type under study. Soil resistance to penetration associated to both management systems showed increased value from one harvest to the next one, being greater for no-tillage system, surpassing the RP value associated to the conventional tillage for the year of 2006. However, obtained values do not interfere in the bean plant productivity for both employed growing system. Values saturated hydraulic conductivity had increased from one harvest to the next, observing that for the year of 2006 no-tillage system showed larger values than the conventional one. Conventional tillage showed lower soil bulk density average values for the year of 2005, however these values became the same for both methods in the year of 2006 harvest. All physical-hydric attributes as well as grain productivity presented spatial dependence for both soil cultivation techniques for both harvesting periods. All of simple linear regressions showed no correlation between attributes and bean production. However, simple linear regressions showed to be significant for attribute maps and production, presenting low determination coefficient values. The best observed result was identified to be the soil density related to production for the conventional crop management, showing the determination coefficient of 43,39 %, i.e., which is considered the best explaining production variation variable. In looking for a model explaining production variation as a function of soil physical-hydric attributes and relief elevation by means of multiple linear regression by the stepwise method, statistically significant models which explains production variation between 27,34 % to 71,70 %

ASSUNTO(S)

irrigation spatial variability solos - umidade time domain reflectometry feijão soil moisture geoestatistic irrigação beans physical-hydric attributes geoestatistica

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