The growth, yield and chemical properties of waxy corn Sonjajang~timesKNU-7 and Asan~timesKNU-7 planted in different dates and mulch types in a converted paddy field was investigated. Experiment was carried out in a randomized complete block design in a split split-plot arrangement with four replications. Planting dates (D) [May 16 (D1, early), June 1 (D2, middle), June 6 (D3, late)] represented main plots, plastic mulch (M) [(BM, black mulch; TM, transparent mulch)] for subplots while waxy corn crosses [Sonjajang~timesKNU-7 (‘Sonja’) and Asan~timesKNU-7 (‘Asan’)] for sub-subplots. Results showed that D had a significant effect on growth characters except emergence, ear quality except ear diameter, and yield whereas M showed significant effect on growth characters only. Superior growth and ear quality performance were recorded in D1 and BM. In terms of crosses, ‘Sonja’ had better growth performance than ‘Asan’ regardless of D and M, but performed better at D1 and BM. Highest yield was obtained in D1 for BM (2,131 kg 10a-1 ) and TM (1,655 kg 10a-1 ) but no significant difference in the yield across V was recorded. In terms of starch and sugar contents, a decreasing trend was observed from D1 to D3 regardless of M and V.

The growth and yield performance of 19 new com hybrids were evaluated. Results showed that all hybrids had a superior growth performance in the drained-paddy than in the upland field except for daeyul × cheongdo and hyoryeong × cheongdo in plant height, cheongdoyeop × wx-3 in tassel1ength, and cheongdo (black) × wx-3 in number of tassel branch. The same hybrids, except cheongdoyeop × wx-3, obtained lower ear quality in drained-paddy field compared to upland in terms of ear weight, and ear and grain setting length. The highest yield in the drained-paddy and upland fields was obtained in the hybrids ks5wx × ks6wx × cheongdo (1,633.3kg · 10a-1) and daeyul × wx-3 (1,516.7kg · 10a-1), respectively. Highest yield among the wx-3 crosses was obtained in daeyul which was 1,583.3kg · 10a-1 and 1,516.7kg · 10a-1 in drained-paddy and upland field, respectively. For the crosses of wx-8, highest yields were recorded in the cultivar bugye50 (1,466.7kg · 10a-1) and seokgu12 (1,384.6kg · 10a-1) for drained-paddy and upland field, respectively. In the case of cheongdo, highest yields were obtained in ks5wx × ks6wx (1,633.3kg · 10a-1) and seokgu14 (1,111.1kg · 10a-1) for drained-paddy and upland field, respectively. Result also showed that the drained-paddy soil had better physicochemical properties than the upland. The relatively high performance in terms of growth parameters and yield of com hybrids planted in the drained-paddy field is in agreement with the higher organic matter and micro-element content of drained-paddy field.

The effect of mixed treatments of wood vinegar and sulfonylurea-based herbicides on weed control, yield and yield components, and quality of rice was investigated. Two herbicides were tested namely: imazosulfuron-ethyl+thiobencarb[ethyl-1-(2-chloroimidazo[1,2-α ]pyridin-3-ylsulfonyl)-3-(4,6-dimethoxypyrimidin-2-yl) urea+S-4-chlorobenzyl diethyl(thiocarbamate)], and bensulfuronmethyl+butachlor [methyl α -[(4,6-dimethoxypyrimidin-2-ylcarbamoyl)sulfamoyl]-o-toluate+N-butoxymethyl-2-chloro-2',6'-diethylacetanilide]. The experiment was carried out in a randomized complete block design with 3 replications and 5 treatments. Treatments used were recommended(RH: 100%) and half-recommended(HRH: 50%) application rates of each herbicide. Half-recommended application rates were combined with 1 mL wood vinegar 500mL~;water-1 (500) and 1 mL wood vinegar 1000mL~;water-1 (1000) wood vinegar. Plots for no herbicide treatments were also prepared and used as control. Results showed that wood vinegar significantly increased efficacy of HRH in bensulfuron-methyl+butachlor while high efficacy was already obtained in HRH treatment of imazosulfuron-ethyl+thiobencarb. Wood vinegar did not improve the efficacy of imazosulfuron-ethyl+thiobencarb but improved rice yield. Significantly similar rice yields were obtained in the HRH+1000 WV and RH treatments of both herbicides. There were no significant variations in the yield components among the treatments; however, differences in yield can be attributed to the variations in the spikelet number and ripening ratio. Data on rice quality analysis did not show clear trend on the effects of the treatments on grain appearance and nutritional quality.