Water-nutrient interactions drive yield and profitability of maize and sorghum under tropical semi-arid conditions

Optimizing supplemental irrigation and mineral fertilization is a key strategy for sustainable agriculture in semi-arid regions. The objective of this study was to assess the yield and profitability of maize and sorghum crops as a function of planting date, supplemental irrigation depth and Nitrogen-Phosphorus-Potassium (NPK) fertilization under the edaphoclimatic scenarios of the tropical semi-arid region. This research was conducted over two rainy seasons (2023 and 2024) in sandy loam soil in Jucás, Ceára State, Brazil, using maize (hybrid AG 1051) and forage sorghum (cultivar BRS Ponta Negra), with water sourced from an alluvial aquifer. The study evaluated two sowing dates (February and March), four supplemental irrigation depths after five days without rain 0 %, 50 %, 75 %, and 100 % of crop evapotranspiration (ETc), and the presence and absence of NPK fertilization. The interaction between NPK fertilization and supplemental irrigation was particularly significant at the late planting date, mainly in 2023, which experienced lower precipitation and longer dry spells. During years characterized by longer dry periods, such as 2023, it is recommended that supplemental irrigation cover 100 % of water requirements in maize crops. Conversely, for forage sorghum in similar dry conditions, a deficit supplemental irrigation providing 60-75 % of ETc is advised. The findings indicate that economic returns and the level of social reproduction (LSR) can be achieved through the combined use of supplemental irrigation and fertilization on areas of 1.0 ha or larger. However, utilizing either supplemental irrigation or fertilization in isolation is not viable, especially for maize cultivation.

Keywords:
water supplementation; mineral fertilization; dry spells; alluvial aquifer; economic analysis