江苏不同熟期粳稻品种的齐穗期和安全播期预测

为明确当前江苏各地不同熟期粳稻品种的安全播期，以江苏的4个熟期类型的5个常规粳稻品种为材料，在江苏连云港(34°83′N)、淮安(33°34′N)、扬州(32°25′N)和苏州(31°18′N)等4地，进行自5月10日起每10天1期，共8个播期的播种试验，得出各播期的相应齐穗期。以齐穗期温光预测模型y=a＋b₁x₁＋b₂x₂拟合其实得的播期与齐穗期资料。用该模型拟合4个试验点、5个供试品种计20组数据，得出20个预测式，其拟合度R²在0.9927~0.9998之间，均达极显著水平。用各试点所在地近25年各年粳稻品种安全齐穗期及逐日平均温度，依齐穗期光温模型预测式经多次迭代推得各年的安全播期，进而求得90%保证率的安全播期并作各地生产应用分析。在江苏淮北的北部，麦稻两熟田水稻的可播栽始期为6月15日，中熟中粳的安全播期为6月21日，此类品种可用于该地直播；其他各熟期类型品种安全播期均早于当地可播栽始期，故不能用于直播。在淮北南部稻麦两熟田的可播栽始期为6月12日左右，中熟中粳和迟熟中粳的安全播期分别在7月4日和6月22日，此两类品种可用于该地麦茬直播；早熟晚粳安全播期在6月17日、18日，在大面积生产中因接茬时间过紧应慎用于麦茬直播；中熟晚粳的安全播期为6月8日，不可用于直播。在苏中南部，水稻可播栽始期为6月8至11日，中熟中粳、迟熟中粳、早熟晚粳类型两品种的安全播期分别在7月12日、3日、6月25日和28日，可用于该地直播；中熟晚粳的安全播期为6月11日，用于直播接茬时间太紧，不可应用。在苏南，水稻的可播栽始期为6月5日，供试4熟期类型品种的安全播期分别为7月18日、13日、9日至10日和7月3日，仅考虑安全齐穗各熟期类型品种均可用于麦茬直播，但因中粳类型品种直播稻生育期过短、产量不高，不宜应用。

Studies on Full Heading and Safe Sowing Date for Different Maturing-type Japonica Rice Cultivars of Jiangsu Province

To know heading dates corresponding to sowing dates of four maturing-type japonica rice cultivars in regions from north to south of Jiangsu Province and to establish the theoretical basis for sowing date arrangement for direct seeding and mechanical transplanting of rice by ascertaining the critical safe sowing dates, we directly seeded five japonica cultivars including Lianjing 4 (mid-maturing and mid-season rice), Huaidao 10 (late-maturing and mid-season rice), Yangjing 4038 (early-maturing and late-season rice), Nanjing 44 (early maturing and late-season rice), and Nanjing 46 (mid-maturing and late-season rice) in Lianyungang (34°83'' N), Huai’an (33°34'' N), Yangzhou (32°25'' N) and Suzhou (31°18'' N) at an interval of ten days from May 10 to July 20. A model y = a + b₁x₁+ b₂x₂ was used to fit the virtual sowing dates and heading dates. Based on the results from four experimental locations and five cultivars, we obtained 20 sets of data, and 20 prediction equations with good fitting degrees of which the values of R² ranged from 0.9927 to 0.9998 were produced. On the basis of annually daily average temperatures and corresponding safe full heading dates of japonica rice during past 25 years, the sowing date for safe full heading was deduced by means of iterating repeatedly, then, a set of safe sowing dates with 90% assurance were evaluated, and the application of the safe sowing dates in various locations was finally analyzed. The results showed that, in a wheat-rice double cropping system of Lianyungang, the earliest sowing or transplanting date was June 15, which was suitable for mid-maturing and mid-season japonica rice cultivars with a safe sowing date of June 21 for direct-seeding; but other maturing-type varieties should have earlier sowing dates and could not be used for direct-seeding. In the south of Huai’an with a rice-wheat cropping system, the earliest date for sowing or transplanting was about June 12, and the safe sowing date was July 4 for mid-maturing and mid-season cultivars and June 22 for late-maturing and mid-season cultivars, and these cultivars could be used for direct-seeding. The safe sowing date was June 17 or 18 for early-maturing and late-season japonica rice cultivars, with a risk of direct-seeding because of a short growing period; the sowing date for safe full-heading of mid-maturing and late-season japonica rice cultivars was June 8, and such cultivars could not be used for direct-seeding. The earliest sowing or transplanting date in the south of central Jiangsu was June 8–11, and the safe sowing date was July 12, July 3, and June 25–28, respectively, for mid-maturing and mid-season, late-maturing and mid-season, and early-maturing and late-season cultivars, and these cultivars could be used for direct-seeding in this district; the safe sowing date of a mid-maturing and late-season cultivar was June 11, and this type of cultivars could not be used for direct-seeding owing to a too short growing period. In the south of Jiangsu, the earliest sowing or transplanting date was June 5, and the safe sowing date was July 18, July 13, July 9–10, and July 3, respectively, for the above four types of cultivars, and all cultivars could be used for direct-seeding if only considering a safe full-heading stage. However, the grain yield could not be high for mid-season cultivars with direct-seeding because they had short growing period.