Atributos do solo sob diferentes sistemas de manejo na região Jaguaribana do Ceará

Abstract

Over time the different uses of the land have contributed to the loss of the chemical, physical and biological quality of the soil, mainly linked to conventional cultivation. If handled incorrectly, this system, by means of excessive operations with agricultural machinery, the application of too many phytosanitary products and fertilizers, or even the use of poor quality irrigation water, can cause enormous damage to soil properties. The objective of the present study was to evaluate the influence of conventional irrigated and rainfed cultivation systems, and in a preservation area, on soil attributes during a cotton production cycle in the Jaguaribana region of Ceará. Agricultural production areas were selected, located in the municipality of Tabuleiro do Norte in the state of Ceará, under conventional irrigated (CCI) and rainfed (CCS) cotton cultivation, as well as a preservation area (AP), close to the cultivated areas. Four composite soil samples were collected from each area in the 0.0 - 0.1 and 0.1 - 0.2 m layers at 65 and 130 days after planting (DAP). The quality of irrigation water was also evaluated, and samples were collected in the same period. Chemical characterization [pH, Ca2+, Mg2+, Na+, K+, H+, Al3+, Cu, Fe, Mn and Zn electrical conductivity (EC) and organic carbon (OC)] and physical [water dispersed clay, flocculation degree, soil density and total porosity] analyses were performed. Water quality assessment was performed based on pH, Ca2+, Mg2+, Na+, K+, electrical conductivity (EC), carbonate, bicarbonate, chloride, and sodium adsorption ratio (SAN) values. Data analysis was performed with descriptive statistics, analysis of variance, and comparison of means by Tuckey's test (P<0.05). Multivariate principal component analysis (PCA) and cluster analysis (PCA) were also performed to explain the relationship between management systems and soil attributes. The statistical programs ASSISTAT 7.7 SIGMAPLOT version 14 and PAST were used. The results showed that the ICC presented an increase of soluble salts in the soil when compared to AP and CCS, due to the addition of salts by irrigation water, although it did not reach the status of a soil affected by salts. The highest soil density and lowest total porosity values were observed in the CCI. The irrigation water was classified as good quality (C2S1) however, with a tendency to contribute to the accumulation of salts