Nutrient Management Strategies for Sichuan

Two on-going monitored village sites continued their study of nutrient management and crop responses in a wheat-corn system at Jianyang and a wheat-rice system at Chongzhou, both in Sichuan Province.

At Jianyang, crop responses to added nutrients were similar to previous years. Nitrogen was still the most limiting nutrient for both wheat and corn. Compared to the optimal (OPT) treatment, wheat yield reductions were the highest with N omission at 1.3 t/ha (-43%) and were similar under P omission (-19%) or K omission (-15%). Corn yields suffered most from K omission, losing 4.5 t/ha (-70%), followed by N omission at 3.0 t/ha (-47%). Meanwhile, P omission was least significant at 927 kg/ha (-15%). This is the fourth year that corn yields were impacted more by K than P. The impact of omitting Mg or Zn has grown with time. Omitting Mg or Zn from the OPT reduced corn yield by 380 kg/ha (-6%) and 758 kg/ha (-12%), respectively. At Chongzhou, N was still most limiting for wheat and rice. Wheat yields were most affected (-1.9 t/ha, or -39%) by N omission, then K (-700 kg/ha, or -14%), then P (-317 kg/ha, or -6%). The smaller response to P might be related to a warm winter in 2008, since crops become less responsive to P under elevated winter temperatures in the subtropical region. Rice yields were also most affected by N omission (-1.3 t/ha, or -32%) and were equally impacted by K or P omission (450 kg/ha, or -15%). The results generated from these long-term experiments indicate that crop yields are most significantly affected by weather and nutrient management. Balanced fertilization is crucial to maintain high crop yield and nutrient use efficiency. Sichuan-NMS-01