Ciencia del suelo
versão On-line ISSN 1850-2067
PILATTI, Miguel Angel; DE ORELLANA, Jorge; DEL CARMEN IMHOFF, Silva e PIRES DA SILVA, Álvaro. Review of the critical limits of the optimal hydric interval. Cienc. suelo [online]. 2012, vol.30, n.1, pp. 09-21. ISSN 1850-2067.
The Optimal Hydric Interval (IHO) is the interval of easily available soil water for the crops, during which soil resistance and aeration do not limit root growth. In this paper, the upper and lower limits of the IHO are discussed. The upper limit is èCC (soil water content at field capacity) when air capacity (èa) is not restrictive for root respiration; otherwise, the limit is èa. The lower limit is determined by the variable of greater value between èRP (soil water content at which soil resistance reduces root elongation) and èFU (soil water easily available by crops below which water stress begins). The validity of the limits is analyzed, and methodological problems for their determination are discussed. Values of the IHO obtained by other authors with different critical limits are compared with those obtained using the values proposed in this study. Each agronomic situation (soil, climate, crops) requires specific values of the IHO that should be calculated for each region. For the northern Pampean Region (Argentina) and the usual crops, the following critical values are proposed: èCC = soil water content at -10 kPa, èa = 15%; èRP = 2,5 to 6 MPa (according to the clay content) and èFU = -0,17 MPa.
Palavras-chave : IHO; NLWR; LLWR; Easy available water; Soil physical quality indicator.