Nitrogen Fertilization Alleviates Barley (Hordeum vulgare L.) Waterlogging

Waterlogging increasingly challenges crop production, affecting 10% of global arable land, necessitating the development of pragmatic strategies for mitigating the downside risk of yield penalty. Here, we conducted experiments under controlled (tank) and field conditions to evaluate the efficacy of nitrogenous fertiliser in alleviating waterlogging stress. Without intervention, we found that waterlogging reduced grain yields, spike numbers and shoot biomass, but had a de minimus impact on grain number per spike and increased grain weight. Soil fertiliser mitigated waterlogging damage, enhancing yields via increased spike numbers, with crop recovery post-waterlogging catalysed via improved tiller numbers, plant height and canopy greenness. Foliar nitrogen spray has little impact on crop recovery, possibly due to stomatal closure, while modest urea application during and after waterlogging yielded similar results to greater N application at the end of waterlogging. Waterlogging-tolerant genotypes (P-17 and P-52) showed superior growth and recovery during and after waterlogging compared to the waterlogging-sensitive genotypes (Planet and P-79). A comparison of fertiliser timing revealed that field fertilizer treatment two (F2: 90 kg<middle dot>ha(-1) at 28 DWL, 45 kg<middle dot>ha(-1) at sowing and 45 kg<middle dot>ha(-1) at 30 DR) yielded the highest and fertilizer treatment three (F3: 45 kg<middle dot>ha(-1) at sowing and 45 kg<middle dot>ha(-1) at 30 DR) recovered the lowest yield and spike number, while fertilizer treatment one (F1: 45 kg<middle dot>ha(-1) at 28 DWL, 45 kg<middle dot>ha(-1) at 0 DR, 45 kg<middle dot>ha(-1) at sowing and 45 kg<middle dot>ha(-1) at 30 DR) and four (F4: 90 kg<middle dot>ha(-1) at 0 DR, 45 kg<middle dot>ha(-1 )at sowing and 45 kg<middle dot>ha(-1 )at 30 DR) had the highest shoot biomass in the field. Treatment five (T5: 180 kg<middle dot>ha-1 at 0 DR, 30 kg<middle dot>ha(-1) at sowing and 90 kg<middle dot>ha(-1) at 30 DR) presented the most favourable results in the tank. Our results provide rigorous evidence that long periods of waterlogging caused significant yield penalty, mainly due to decreased spike numbers. We contend that increasing fertiliser rates during waterlogging up to 90 kg<middle dot>ha(-1) can provoke crop growth and mitigate waterlogging-induced grain yield losses, and is more beneficial than applying nitrogen post-waterlogging.