Straw/Grain Ratio of Wheat and Vertical Distribution of Wheat Straw in Jiangsu Province

In order to define total and characteristics of spatial distribution of the wheat straw resources in Jiangsu Province, investigations were done of straw resources of 13 varieties of spring wheat and 19 varieties of semi-winter wheat, commonly cultivated in Jiangsu. Samples of wheat straw were cut generally into 5 sections, 5 cm each, beginning from the basal node, 0-5, >5-10, >10-15, 15-20 and >20cm, dried and weighed separately and the spikes were threshed, leaving hull and rachis (Section 6), which were dried and weighed, too. On such a basis, analysis was done of straw/grain ratio and proportion of each section of straw to the whole wheat straw in biomass in relation to wheat variety and yield, Results show that the varieties of spring wheat were much lower than those of semi-winter wheat in straw/grain（S/G）ratio . The former was 1.05- 1.07 and the latter was 1.38 - 1.40 on average. However, both the two ecological types of wheat decreased in S/G ratio with increasing yield. The varieties of spring wheat varied in the range of 0.96 - 1.42, while those of semi-winter wheat did in the range of 1.21 -1.77. The variation differed from year to year. In the 2010 ~ 2011 wheat season, the crops low in yield (4000-6250 kg·hm^-2) were significantly higher in S/G than those super-high in yield (> 8500 kg·hm^-2), while in the 2012-2013 wheat season, no big difference in S/G between crops high or low in yield. The two varieties of wheat, different in eco-type, differed, too, in spatial distribution of straw. The proportion of the six parts (5 sections of straw and spike) was 8.00%, 7.06%, 6.64%, 6.57%, 48.00% and 23.75%, respectively, of the total of a whole spring wheat plant, and 10.11%, 8.07%, 7.39%, 7.06%, 44.53% and 22.85%, respectively, of the total of a whole semi-winter wheat plant. When the crop varied within the range from 4750 to 8500 kg·hm^-2 in yield, the proportions of the six parts of plant did not change much, but when the crop was super high in yield (>8500 kg·hm^-2), the proportion of Section 6 was significantly lower than that when the crop was low in yield (4000-4750 kg·hm^-2). The S/G and straw distribution of wheat in Jiangsu Province are much affected by eco–type and grain yield level of the wheat.