Abstract
In arid and semi-arid regions, due to the low rainfall and high evapotranspiration rate, salts are concentrated in the soil and in the water, causing the salinization of the medium. Irrigation is necessary in these regions, but the volume required by the crops is high. Deficit irrigation is an alternative since it alleviates plant stress, but without affecting the crop yield. Sorghum is a plant that tolerates soil moisture deficit and surplus. The objective of this work was to verify the influence of irrigation water salinity and depth in the sorghum (Sorghum bicolor (L.) Moench) crop in terms of yield. The experiment was conducted from February to May 2016, in the municipality of Mossoró / state of Rio Grande do Norte. The treatments studied consisted of three factors as follows: irrigation water salt concentration (ECw) of 0.8, 2.4, 3.43 and 4.81 dS m-1; irrigation depths of 80, 98 and 127% of ETc applied via drip irrigation; and BRS 506, IPA 2502 and Ponta Negra sorghum cultivars, arranged in a (4x3)x3 factorial scheme with split plots, cultivars in sub-plots, with four blocks. Supplemental irrigations were implemented, being around 9% of the crop demand supplied by rainfall that occurred in the period. Soil electrical conductivity presented a reduction tendency when larger water volumes were applied. Irrigation depth and salinity did not influence yield aspects, even with a 20% reduction in the ideal irrigation depth and water salt concentration of at least 4.81 dS m-1 of electrical conductivity.
Highlights
Nowadays, water scarcity is largely experienced mainly in the Northeast Region of Brazil, compromising the entire production chain
In regard to electrical conductivity of the soil saturation extract, in the 0 - 0.6 m deep layer, a significant effect was identified for the following interactions: irrigation depth and irrigation water salinity, sorghum cultivar and irrigation depth, and sorghum cultivar and irrigation water salinity
Lima et al (2007), in their study about how the cowpea responds to different irrigation water salinities, found a linear adjustment for ECe, where the increment of 0.5 to 5 dS m-1 resulted in an ECe increase of 105.4%, indicating that as the irrigation water salt concentration is increased, there is an increment in the soil salt concentration
Summary
Water scarcity is largely experienced mainly in the Northeast Region of Brazil, compromising the entire production chain. Sustainable agricultural practices in arid and semi-arid regions depend, among other practices, on the use of irrigation, due to climate instability. Due to the intense human pressure for good quality water and the increasing need for expansion of agricultural production worldwide, the use of low quality water has increased (NOBRE et al, 2011). Due to the need of increasing production, associated with the restricted water volume available for irrigation, mainly in the semi-arid region, where there is irregular distribution and low volume of rainfall, the deficit irrigation represents an alternative, especially for crops as sorghum (Geerts & Raes, 2009; Barros et al, 2013). Sorghum is regarded as a strategic crop for regions or areas with water restriction, due to its higher abiotic stress tolerance, in addition to its moderate salinity tolerance (Dias & Blanco, 2010). That is the reason why the sorghum is considered an alternative for different products, such as the production of forage material, grains, ethanol and sugar (COSTA et al, 2019)
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