Comparison of matter production and the light and temperature resources utilization efficiencies of the main cropping systems for paddy fields in the Dongting Lake region

Reasonable cropping systems can match crop growth demand and natural resource supply. This comparison of the main cropping systems for paddy fields aims to identify the dominant cropping system in the Dongting Lake area and to provide a theoretical basis for optimizing resource allocation and the establishment of high-yield and high-efficiency planting patterns. From 2016 to 2018, four main cropping systems for paddy fields in the lake area were selected as research objects. The efficiency and energy of dry matter production, light and temperature resource utilization efficiencies, and the economic benefits of different patterns were analyzed. Among the four modes, the winter fallow-middle rice one-cropping system had the lowest year-round average efficiency and energy of dry matter production, and distribution rates of effective accumulated temperature and light energy distribution, which were 18.330 kg·hm⁻² and 27.00 MJ·m⁻², 70.0% and 49.2%, respectively, indicating that the winter fallow-middle rice system did not fully utilize the light and temperature resources and that the efficiency and energy of dry matter production were low. The oilseed rape-early rice-late rice triple-cropping system had the highest year-round average efficiency and energy of dry matter production, which were 31.525 kg·hm⁻² and 48.22 MJ·m⁻², respectively, but the year-round average growth period was 364.5 days. The distribution rates of year-round effective accumulated temperature and light energy from 2016 to 2017 reached 102.5% and 102.6%, respectively, indicating that the oilseed rape-early rice-late rice system lacked light and temperature resources and that it was difficult to meet the demands of the three crops. The triple-cropping system had the lowest net income, with an average of 8738 ¥∙hm^–2 over two years. The growth season of the winter fallow-early rice-late rice system was concentrated from early April to mid-to-late October. In winter, temperature and light resources were wasted. The year-round average net income of the winter fallow-early rice-late rice system was 9009 ¥·hm⁻², which was only 75.3% of the winter fallow-middle rice system and 62.3% of the oilseed rape-middle rice system. The time for oilseed rape-middle rice double-cropping system was available throughout the whole year, with an average utilization rate of 88.9%, and the year-round average distribution rates of effective accumulated temperature and light energy were 86.6% and 87.7%, respectively. The highest net income for oilseed rape-middle rice was 14 468 ¥·hm⁻², which was obviously higher than that of the other three models. Compared to the other three models, the oilseed rape-middle rice two-cropping system could make full use of the light and temperature resources, and the efficiency and energy of dry matter production were higher. It was also the highest net income model and suitable for development in the Dongting Lake area.