In-Seok Oh

Effect of Green Manure Hairy vetch on Rice Growth and Saving of Irrigation Water

Green manure crops are primarily used to reduce the application of chemical fertilizers. In this study, a two-year field experiment was conducted to evaluate the effects of green manure hairy vetch on rice growth and saving of irrigation water. This experiment was conducted at Sinheung series (fine loamy, mixed, nonacid, mesic family of Fluvaquentic Endoaquepts) from 2008 to 2009 at the National Institute of Crop Science (NICS), RDA, Suwon, Gyeonggi province, Korea. Hairy vetch as a green manure crop was incorporated in soil for rice cultivation. Chemical fertilizers had not been applied to hairy vetch plot. Treatments included once irrigation (OI) per week and conventional irrigation (CI). In 2008, the water use efficiency of OI increased by 46% compared to CI by hairy vetch application during rice cultivation season (water treatments were started 38 days after rice transplanting). In 2009, the water use efficiency of OI increased by 61.3% compared to CI by hairy vetch application during rice cultivation season (water treatments were started 30 days after rice transplanting). Soil physical properties such as bulk density, soil porosity ratio and glomalin contents were improved by the incorporation of hairy vetch. The rice yield of OI water management was not significantly different from those of CI water management by hairy vetch application both years. These results suggest that the OI water management with hairy vetch incorporated in soil for rice cultivation can be used in rice fields to reduce the amount of irrigation water and chemical fertilizer.

Effect of Biomass and N Production by Cultivation Methods of Leguminous and Gramineae Green Manures on Rice Growth in Central Regions of Korea

The cultivation methods are important for determining crop yield of green manure. The effect of cultivation methods of green manure crops (GMC) on biomass and rice yield was investigated. This experiment was conducted at Sinheung series (fine loamy, mixed, nonacid, mesic family of Fluvaquentic Endoaquepts from Oct. 2007 to Oct. 2008 at the National Institute of Crop Science (NICS), RDA, Suwon, Gyeonggi province, Korea. Seven GMC (hairy vetch, barley, Chinese milk vetch, rye, crimson clover, oats, rattail fescue) were cultivated and incorporated on paddy soil by broadcasting before rice harvesting (BBRH) and partial tillage seeding (PTS). Among the three leguminous GMC, the biomass and N production were the highest at the hairy vetch of PTS. Among the four gramineae GMC, the biomass and N production tended to be higher in the rye of BBRH and barley of PTS. The C/N ratio (56.5～74.2) of rye was high compared with hairy vetch (14.1). Among the GMC, the incorporation of hairy vetch increased NH4-N contents in rice paddy soil at 14 and 42 days after transplanting. These results showed that hairy vetch had no significant to rice yield compared with conventional fertilization. Therefore, hairy vetch seems to be the most efficient green manure crop as an alternatives to chemical N fertilizer in the central regions of Korea.

Effect of Monoculture and Mixtures of Green Manure Crimson Clover (Trifolium incarnatum) on Rice Growth and Yield in Paddy

Green manure crops are mainly used to reduce the application of chemical fertilizers. Mixture of green manure crops have beneficial effects in agroecosystem. In this study, experiments were conducted to evaluate the effects of monoculture and mixtures of crimson clover (Trifolium incarnatum) on rice growth and yield in paddy. This experiment was conducted at Sinheung series (fine loamy, mixed, nonacid, mesic family of Fluvaquentic Endoaquepts) from Oct. 2007 to Oct. 2009 at the National Institute of Crop Science (NICS), RDA, Suwon, Gyeonggi province, Korea. Seeding rates of crimson clover (CC) were consisted of monoculture (CC2, 3, 4 kg and hairy vetch 5 kg ) and mixtures (CC 2 + barley 7, CC 3 + barley 7, CC 4 + barley 7, and CC2 + hairy vetch ). Seeds were drilled by partial tillage machine on 9th Oct. in 2007. Monoculture and mixture of crimson clover as a green manure crop was incorporated in soil for rice cultivation on 15th May in 2008. Chemical fertilizers had not been applied to monoculture and mixture plots. The biomass and N production of monoculture plots were lower than mixture plots. The biomass and N production of CC 2 + hairy vetch plot were the highest among mixtures treatments. In rice growing season, ammonium nitrogen concentrations in soil were a little high trends at CC 2 + hairy vetch plot. And soil bulk density and porosity were improved at mixture plot after rice harvesting. The rice yield of CC 2 + hairy vetch plot was not significantly different from conventional practice plot. These results indicated that cropping of crimson clover with hairy vetch mixture was better than barley mixture for environmental friendly rice cultivation.

Response of Millet and Sorghum to Water Stress in Converted Poorly Drained Paddy Soil

Millet and sorghum are major dryland cereal crops, however their growth and productivity is limited by soil water stress with varying intensity. The major objective of this study was to evaluate water stress of millet and sorghum yield under drainage classes of poorly drained soil and to test the effect of the installed pipe drainage in poorly drained paddy soil to minimize crop stress. The research was carried out in poorly drained paddy fields located at alluvial slopping area resulting in non-uniform water content distribution by the inflow of ground water from the upper part of the field. Stress Day Index (SDI) was determined from a stress day factor (SD) and a crop susceptibility factor (CS). SD is a degree of measurement by calculating the daily sum of excess water in the profile above 30cm soil depth (SEW30). CS depends on a given excess water on crop stage. The results showed that sum of excess water day (SWD30) used to represent the moisture stress index was lower on somewhat poorly drained soil compared with poorly drained soil on 117 days. CS values for sorghum were 57% on 3rd leaf stage, 44% on 5 th leaf stage, 37% on panicle initiation, 23% on boot stage, and 16% on soft dough stage. For proso millet CS values were 84% on 3 rd leaf stage, 70% on 5 th leaf Stage, 65% on panicle initiation, 53% on boot stage, and 28% on soft dough stage. And for foxtail millet the values were 73% on 3 rd leaf stage, 61% on 5 th leaf stage, 50% on panicle initiation, 29% on boot stage, and 15% on soft dough stage. SDI of sorghum and millet was more susceptible to excess soil water during panicle initation stage more poorly drained soil than somewhat poorly drained soil. Grain yield was reduced especially in proso millet and Foxtail millet compared to Sorghum.

Changes of Soil Physical Properties by Manured Sorghum Residues Incorporation

Although sorghum residue production was estimated to be 8～10 Mg ha -1 , most sorghum straw was used to be burnt or removed after harvest. This experiment was conducted to evaluate the effect of the incorporation of manured sorghum residues on soil physical properties from 2010 to 2012 in the converted paddy field. Five treatment with 3 replication consisted of control, inorganic fertilizer (NPK), manured residues, sorghum stover and sawdust manure. The incorporation level of organic source was 10 Mg ha -1 without inorganic fertilizer NPK. The investigated physical parameters were bulk density (BD), porosity, water stability aggregate (WSA), water infiltration rater (WIR), penetration resistance (PR) and soil water retention characteristics (WRC) with soil depth. The incorporation of manured sorghum residues improved WIR significantly over inorganic fertilizer (NPK), sorghum residues and sawdust manure. The BD by incorporating with manured residues on sorghum was reduced significantly with crop residue over plot of NPK and sawdust. Significant increase in WSA was observed with stubble incorporation alone or manured sorghum residues. Soil WRC were significantly enhanced with manured sorghum residue incorporated without NPK. The average PR at 0～15 cm was 0.54 MPa for manured sorghum residues. For sawdust manure plot it was 0.42 MPa, for Sawdust manure plot 0.39 MPa and for NPK plot 0.54 MPa.