Estratégias produtivas em cultivo de sequeiro e reuso de água residuária para convivência com a escassez hídrica, Pernambuco (Brasil)

Abstract

The strong trend in increasing the variability of rainfall and increasing water scarcity produce an increase in the uncertainties for rainfed agricultural production, as well as social unrest regarding the use of good quality water in irrigated agriculture, resulting in pressures for the use of alternatives such as conservation practices of soil moisture and the use of inferior water for irrigation, with emphasis on wastewater, which in turn is increasingly abundant, and being directly discharged into water bodies without proper treatment, representing a potential resource for agricultural production of forage plants, through a previous treatment. Thus, the objective of this research is to evaluate the effects of climatic conditions for the Brazilian Northeast that provide subsidies for the use of water and soil conservation strategies in corn cultivation in rainfed systems, as well as for the use of waste water in agricultural production and environmental protection in a hydrographic basin in the semiarid region of Pernambuco. Chapter 1 covers the general and specific introduction, hypotheses and objective and the literature review. Chapter 2 provides an analysis of climate change for the Brazilian Northeast in relation to annual precipitation, rainy days and temperature. Due to the effects of climate change, Chapter 3 addresses the spatial variability in soil and corn plants grown in the traditional system (without applying mulch as a soil moisture conservation practice) and with mulch. Chapter 4 assesses the effect of applying 5 irrigation slides with wastewater (60, 80, 100, 120 and 140% of the Evapotranspiration of Culture - ETc) in 4 conditions of soil cover (without cover (control), native vegetation) , coconut powder and macerated moringa seeds) in the development of Sorghum sudanense (Piper) Stapf, in the salinity of the soil, groundwater and total organic carbon. Chapter 5 addresses the effect of spatial and temporal dependence on the productive parameters of sorghum, moisture and electrical conductivity of the soil in an area irrigated with wastewater in the presence and absence of mulch. Chapter 6 presents results of production of corn, sunflower and sorghum irrigated with treated domestic sewage, with the participation of rural farmers and elementary school students. Finally, chapter 7 contains the general conclusions of the Thesis. This Thesis presents important results on the current and future effects on changes in the patterns of rain, rainy days and temperature in northeastern Brazil, with emphasis in the semiarid region, which presents high water scarcity and strategies for living with the future scenarios, the use of mulch represents an essential practice to mitigate the effects of climate change and improve agricultural production. In addition, the use of treated wastewater for agricultural crops, especially forage sorghum, represents an important alternative for irrigated agriculture, especially in conjunction with the use of mulch, since it promotes better incorporation of organic matter in the soil and greater preservation of spatial and temporal correlation between sorghum and soil growth variables. Through participatory management, actions aimed at intensifying the use of domestic effluents and sewage sludge for hydro-agricultural purposes should be encouraged, promoting food production and increasing income for agricultural producers.