Closing Yield Gaps through Soil Improvement for Maize Production in Coastal Saline Soil

As efforts to close crop production yield gaps increase, the need has emerged to identify cost-effective strategies to reduce yield losses through soil improvement. Maize (<i>Zea mays</i> L.) production in coastal saline soil is limited by high salinity and high pH, and a limited number of soil amendment options are available. We performed a field experiment in 2015 and 2016 to evaluate the ability of combined flue gas desulfurization gypsum and furfural residue application (CA) to reduce the maize yield gap and improve soil properties. We carried out the same amendment treatments (CA and no amendment as a control) under moderate (electrical conductivity (EC_1:1) &#8776; 4 dS m^&#8722;1) and high (EC_1:1 &#8776; 6 dS m^&#8722;1) salinity levels. Averaged over all salinity levels and years, maize yields increased from 32.6% of yield potential in the control to 44.2% with the CA treatments. Post-harvest CA treatment increased the calcium (Ca²⁺) and soil organic carbon (SOC) contents while decreasing the sodium (Na⁺) content and pH in the upper soil layer. Corresponding nitrogen, phosphorus, potassium, calcium, and magnesium accumulations in maize were significantly increased, and Na accumulation was decreased in the CA group compared with the control. The economic return associated with CA treatment increased by 215 $ ha^&#8722;1 at the high salinity level compared with the control, but decreased at the moderate salinity level because of the minor increase in yield. The results of this study provide insight into the reduction of yield gaps by addressing soil constraints.