Boron rates and residual effect of gypsum on soil chemical attributes and barley yield

ABSTRACT Studies on barley management practices are scarce, and farmers have employed boron (B) fertilization without technical criteria, relying primarily on field reports of yield gains. This study aimed to assess the efficacy of B fertilization of barley cultivars (cv.) under the residual effect of phosphogypsum. The experiment was started in 2009 using a randomized block design, with rates of 0, 3, 6, 9, and 12 Mg[gypsum] ha–1 for a long-term study. The plots were divided into four sections in the 2021 and 2022 winter seasons, each receiving a different B rate: 0, 1, 2, and 4 kg[B] ha–1 as boric acid (H3BO3). The barley cv. Danielle and Imperatriz were then sown in these sections. The data were analyzed using a split-split plot design. The yield components and grain yield were evaluated in Nov 2021 and 2022, while the soil was sampled following the barley harvest in 2022. The residual effects of gypsum on the evaluated soil chemical properties were nearly negligible, except for the yield of cv. Imperatriz, which exhibited an increase with gypsum rates in 2021, while no yield response was observed for cv. Danielle (2021 and 2022). The B fertilization increased soil-B availability and the yield of cv. Danielle in 2021 and 2022, while cv. Imperatriz exhibited an increase in yield only in the 2021 season. The cv. Imperatriz exhibited a higher yield than cv. Danielle in 2021 and 2022 seasons, with an increase of 18 % on average. The increases in soil B content (0.37 - 0.45 mg[B] dm–3) and in grain yield as a result of B fertilization of barley cv. Danielle (+17 – 87 %) and Imperatriz (up to +6 %) indicate that the current critical soil B level (0.3 mg[B] dm–3) should be reevaluated in the southern states in Brazil.