Tillering Characteristics of Indica Hybrid Rice under Mechanized Planting

In order to explore tillering characteristics and its relationships with yield of indica hybrid rice with mechanized planting and different sowing dates, a split plot field experiment was conducted using F you 498 with mechanized direct-seeding, mechanized transplanting and artificial transplanting and two sowing date treatments. The main results are as follows:(1) The major and stable contribution to yield was from primary tillers group, ranging from 58.67% to 63.82% among different planting methods. The contribution to yield from main stem was significantly different, with the highest in mechanized direct-seeding and the lowest in artificial transplanting. Yield of secondary tillers group was much lower in mechanized direct-seeding than in mechanized and artificial transplanting.(2) The tillering and panicle formation pattern was different for different planting methods which had a changing trend with a single peak for mechanized direct-seeding and transplanting and with two peaks for artificial transplanting. Tillers of mechanized direct-seeding had early and fast emergence and its primary tillers group emerged from leaf 1 to leaf 8, among which tillers from leaf 1 to leaf 4 had higher percentage of emerging and earbearing, and secondary tillers group earbeared mainly in leaf 1 and leaf 2. Tillers of mechanized transplanting had relatively late, low and concentrated emergence, the primary tillers group mainly emerged from 3/0 to 8/0, among which leaf position of 3/0 to 6/0 had higher rate of panicle formation, and secondary tillers group emerged and earbeared mainly in leaf 3, leaf 4, and leaf 5. The number of tillering leaf positions of artificial transplanting was more and tillering time was longer in seeding bed and field. The primary tillers group mainly emerged from leaf 1 to leaf 8 besides leaf 3, among which the tillers of leaf 1, leaf 2, leaf 4, leaf 5, and leaf 6 had higher earbearing per-centage, secondary tillers group emerged and earbeared mainly in leaf 1 and leaf 2. The number of tillering and earbearing leaf positions and yield decreased with delaying sowing date.(3) The main stem and primary tillers in low and middle earbearing leaf positions had larger number of earbearing tiller branches, spikelets per panicle, grain weight and grain weight per panicle among three planting methods. The number of earbearing tiller branches and spikelets per panicle of secondary tillers and primary tillers in high earbearing leaf positions were fewer, so their panicles were small. Leaf 1 to leaf 4 in mechanized direct-seeding, leaf 3 to leaf 6 in mechanized transplanting and leaf positions of 1, 2, 4, 5, and 6 in artificial transplanting were the superior leaf positions. Their contributions to yield were 70.51%, 73.83%, and 76.81%, respectively. The tillers group of superior leaf positions in each planting method had higher rates of tiller emerging and panicle formation, larger panicles and higher contribution to yield. Thus, we should optimize agronomic measures for tillers of superior leaf positions to increase yield potential.