Different characteristics of nutrient absorption and utilization between inbred japonica super rice and inter-sub-specific hybrid super rice

Although previous researchers have revealed that inter-sub-specific hybrid rice between indica and japonica has super-high yield potential, the mechanisms underlying nutrient absorption and utilization remain limited. The present study assessed nutrient accumulation and utilization, root morphology, and physiology of inter-sub-specific hybrid super rice cultivars (IHSRC) Yongyou 12 and Yongyou 15, using inbred japonica super rice cultivars (IJSRC) Nanjing 44 and Ningjing 3 as control. Total nitrogen (N), phosphorus (P), and potassium (K) accumulations in IHSRC were 12.53%, 20.81%, and 17.30% higher than those in IJSRC respectively. The larger amounts of accumulated nutrients in IHSRC were mainly attributable to the high rates of nutrients accumulation before elongating and the long growth duration without premature senescence after elongating. The apparent recovery efficiency of N fertilizers, agronomic N use efficiency, and the partial factor productivity of applied N in IHSRC were all higher than those in IJSRC, whereas the physiological N use efficiency and internal N, P, and K use efficiencies of IHSRC were similar to or lower than those of IJSRC. Compared with IJSRC, the root weights of IHSRC were heavier with greater length and bigger volume, the total and active absorption areas were also larger. In conclusion, with strong and active root systems, IHSRC are more efficient in nutrient absorption than utilization.