Han-Yong Kim

Dry matter and nitrogen accumulation and partitioning in rice (Oryza sativa L.) exposed to experimental warming with elevated CO2

Effects of elevated CO2 concentration ([CO2]) and air temperature (Tair) on accumulation and intra-plant partitioning of dry matter (DM) and nitrogen in paddy rice were investigated by performing a pot experiment in six natural sunlit temperature gradient chambers (TGCs) with or without CO2 fumigation. Rice (Oryza sativa L.) plants were grown in TGCs for a whole season under two levels of [CO2] (ambient, 380xa0ppm; elevated, 622xa0ppm) and two daily Tair regimes (ambient, 25.2°C; elevated, 27.3°C) in split-plot design with triplication. The effects of elevated [CO2] and Tair on DM were most dramatic for grain and shoot with a significant (Pu2009<u20090.05) interaction between [CO2] and Tair. Overall, total grain DM increased with elevated [CO2] by 69.6% in ambient Tair but decreased with elevated Tair by 33.8% in ambient [CO2] due to warming-induced floral sterility. Meanwhile, shoot DM significantly increased with elevated Tair by 20.8% in ambient [CO2] and by 46.6% in elevated [CO2]. Although no [CO2]u2009×u2009Tair interaction was detected, the greatest total DM was achieved by co-elevation of [CO2] and Tair (by 42.8% relative to the ambient conditions) via enhanced shoot and root DM accumulation, but not grain. This was attributed largely both to increase in tiller number and to accumulation of photosynthate in the shoot and root due to inhibition of photosynthate allocation to grain caused by warming-induced floral sterility. Distribution of N (both soil N and fertilizer 15N) among rice parts in responding to climatic variables entirely followed the pattern of DM. Our findings demonstrate that the projected warming is likely to induce a significant reduction in grain yield of rice by inhibiting DM (i.e., photosynthates) allocation to grain, though this may partially be mitigated by elevated [CO2].

Natural 15N abundance of paddy rice (Oryza sativa L.) grown with synthetic fertilizer, livestock manure compost, and hairy vetch

Nitrogen isotope abundance (δ15N) of paddy rice (Oryza sativa L.) grown for 110xa0days after transplanting (DAT) under field conditions with ammonium sulfate (AS with −0.4‰ as a synthetic fertilizer), pig manure compost (PMC with 15.3‰ as a livestock manure compost), and hairy vetch (HV with −0.5‰ as a green manure) was investigated to test the possible use of δ15N technique in discriminating organically grown from conventionally grown rice. At 15 DAT, the δ15N of whole rice decreased (Pu2009<u20090.05) in the order of 10.5‰ for PMC > 5.5‰ for control (without N input) > 4.0‰ for HV > 1.8‰ for AS. This difference seemed to reflect primarily the δ15N signal of N sources. Although differences in δ15N of rice grown with isotopically distinct N inputs (i.e. PMC vs. AS and PMC vs. HV) became smaller over time, the difference (2.8 and 3.0‰ difference at harvest on 110 DAT, respectively) was still significant (Pu2009<u20090.05). However, there was no distinguishable difference between AS and HV treatment after 42 DAT. Such effect of N inputs on δ15N of whole rice was also observed for root, shoot, and grain at harvest. Therefore, our study suggests that it is possible to distinguish rice grown with manure composts from that grown with synthetic fertilizers. However, if green manure of preceding N2-fixing plants is used as the N source, δ15N of rice may not be a good surrogate of N sources.

Nitrogen and carbon isotope responses of Chinese cabbage and chrysanthemum to the application of liquid pig manure

The effects of the liquid pig manure (LM) used in organic farming on the natural abundance of 15N and 13C signatures in plant tissues have not been studied. We hypothesized that application of LM will (1) increase δ15N of plant tissues due to the high δ15N of N in LM as compared with soil N or inorganic fertilizer N, and (2) increase δ13C of plant tissues as a result of high salt concentration in LM that decreases stomatal conductance of plants. To test these hypotheses, variations in the δ15N and δ13C of Chinese cabbage (Brassica campestris L.) and chrysanthemum (Chrysanthemum morifolium Ramatuelle) with two different LMs (with δ15N of +15.6 and +18.2‰) applied at two rates (323 and 646xa0kgxa0Nxa0ha-1 for cabbage and 150 and 300xa0kgxa0Nxa0ha-1 for chrysanthemum), or urea (δ15Nxa0=xa0-2.7‰) applied at the lower rate above for the respective species, in addition to the control (no N input) were investigated through a 60-day pot experiment. Application of LM significantly increased plant tissue δ15N (range +9.4 to +14.9‰) over the urea (+3.2 to +3.3‰) or control (+6.8 to 7.7‰) treatments regardless of plant species, strongly reflecting the δ15N of the N source. Plant tissue δ13C were not affected by the treatments for cabbage (range −30.8 to −30.2‰) or chrysanthemum (−27.3 to −26.8‰). However, cabbage dry matter production decreased while its δ13C increased with increasing rate of LM application or increasing soil salinity (Pxa0<xa00.05), suggesting that salinity stress caused by high rate of LM application likely decreased stomatal conductance and limited growth of cabbage. Our study expanded the use of the δ15N technique in N source (organic vs. synthetic fertilizer) identification and suggested that plant tissue δ13C maybe a sensitive indicator of plant response to salinity stress caused by high LM application rates.

Soil and plant nitrogen pools in paddy and upland ecosystems have contrasting δ15N

Waterlogged paddy and water-unsaturated upland ecosystems have contrasting soil nitrogen (N) processes that affect the natural 15N abundance (15N/14N, expressed as δ15N) in different N pools. In this study, we investigated the δ15N patterns in soil and plant N pools of paddy and upland ecosystems. Samples were collected from 20 each of paddy and upland fields at the active growing season and analyzed for N concentration and δ15N. The higher (Pu2009<u20090.001) concentration (22.1xa0mgxa0Nxa0kg−1) and lower δ15N (6.9xa0‰) of NH4+ in paddy than in upland soils (6.1xa0mgxa0Nxa0kg−1 and 9.2xa0‰, respectively) likely reflected the lower nitrification potential in paddy soils. On the other hand, a higher (Pu2009<u20090.001) δ15N of NO3− in paddy (12.7xa0‰) than in upland soils (4.7xa0‰) indicated higher denitrification rates in paddy soils. The positive (Pu2009<u20090.01) correlation of the δ15N of soil organic N with the δ15N of NH4+ rather than with that of NO3− suggested a tight linkage between organic N and NH4+ as a result of immobilization-mineralization turnover of NH4+. Therefore, in waterlogged paddy soils where nitrification was restricted, a high rate of microbial immobilization-mineralization turnover might lead to a lower δ15N of soil N (total N, organic N, and NH4+) than those for upland. The δ15N in plant N pools also reflected the dominant mineral N species in paddy (NH4+) and upland soils (NO3−). We conclude that contrasting soil N processes (particularly nitrification) leave distinct δ15N signatures in the soil and plant N pools between paddy and upland fields.

Further Understanding of the Impacts of Rainfall and Agricultural Management Practices on Nutrient Loss from Rice Paddies in a Monsoon Area

As rice paddies are widespread sources of water pollution in the agricultural regions of the Asian monsoon area, a mechanistic understanding of nutrient loss from paddies is critical for water quality management. A 2-year experiment was conducted in a typical monsoon-affected rice field to improve our understanding of the impacts of rainfall and agricultural management practice on nitrogen (N) and phosphorus (P) loss. Samples of paddy drainage water were collected during rainfall events (nu2009=u200925) and analyzed for total N (T-N) and total P (T-P) concentrations. The impacts of rainfall (amount, duration, and intensity) and agricultural management practice (transplanting and fertilization) on the event mean concentration (EMC) and loss of nutrient were assessed using regression analyses. The results showed that T-N and T-P concentrations were affected by agricultural practice; meanwhile, loss of T-N and T-P was correlated with rainfall characteristics. Specifically, the EMC of T-N but T-P was negatively (pu2009<u20090.001) correlated with the number of days after agricultural practice in both years, which likely represents a decrease in nutrient availability in paddy water over time. Loss of T-N and T-P was positively (pu2009<u20090.01) correlated with rainfall amount, and this suggests that the rainfall-runoff process is a key driver of nutrient loss in the study area. Our results suggest that rainfall amount and days after transplanting need to be taken into account when estimating nutrient loss from rice paddies in monsoon regions.

Fertilizer N uptake of paddy rice in two soils with different fertility under experimental warming with elevated CO2

Background and aimsOnly limited information is available in the research area on the effect of elevated CO2 concentration ([CO2]) and air temperature (Tair) on the fertilizer N uptake by rice. This study was conducted to investigate changes in rice uptake of N derived from fertilizer (NDFF) and soil (NDFS) as well as fertilizer N uptake efficiency (FUE) with elevated [CO2] and Tair in two soils with different fertility.MethodsRice (Oryza sativa L.) plants were grown with 15N-urea for two growing seasons (2007 in the less fertile and 2008 in the more fertile soil) in temperature gradient chambers under two (ambient and elevated) levels of [CO2] and Tair regimes. At harvest, dry matter (DM) and N uptake amount of rice compartments (root, shoot, and grain) were determined.ResultsThe DM of whole rice increased (Pu2009<u20090.01) with co-elevation of [CO2] and Tair in both years (by 28.0xa0% in 2007 and by 27.4xa0% in 2008). The DM in 2008 was greater than that in 2007 by 48.1 to 63.1xa0% probably due to better soil fertility as well as longer sunshine hours (456xa0h vs. 568xa0h). Co-elevation of [CO2] and Tair increased total N uptake, NDFF, and NDFS by 19.4 to 29.1xa0% in general compared to the ambient conditions. The FUE increased with co-elevation of [CO2] and Tair from 46.5 to 59.5xa0% in 2007 and from 36.7 to 43.8xa0% in 2008.ConclusionsThe projected global warming with elevated [CO2] is expected to increase FUE via enhanced DM accumulation with less increments in the soils that have higher indigenous soil N availabilities.

High-Time Resolution Analysis of Diel Variation in Methane Emission from Flooded Rice Fields

Methane (CH4) emission from flooded rice fields was measured hourly over 24 h for rice (Oryza sativa L.) seasons in 2008 and 2009. The objectives of this study were to identify typical diel variation in CH4 emission and to estimate the best time of day for optimum extrapolation of daily CH4 emission. Our results showed distinct diel variation in CH4 emission, which exhibited a maximum at 14:00–15:00 and a minimum at midnight. About 5.2–5.6% of total CH4 emitted per day (110–160 mg CH4 m−2 d−1) was released at 14:00–15:00. The diel pattern of CH4 emission resembled that of air temperature (Ta). The Ta coupled with solar radiation could cause a difference in partial pressure of CH4 (DPPC) through the gas conduit of the plant. The best extrapolation of daily CH4 emission was achieved with data observed at 10:00–11:00. We concluded that DPPC-induced CH4 emission is an important mechanism causing diel variation. Present address of Seok-In Yun, Department of Bio-Environmental Chemistry, Wonkwang University, 460 Iksandae-ro, Iksan, Jeonbuk 570-749, Korea.

Soil and Compost Type Affect Phosphorus Leaching from Inceptisol, Ultisol, and Andisol in a Column Experiment

A column leaching experiment using three soils (Inceptisol, Ultisol, and Andisol) and seven livestock manure composts that had different characteristics was conducted for 19 weeks to investigate the interactive effects of composts and soils on the phosphorus (P) leaching potential of compost-amended soils and to identify the principal variables that affect P leaching. Cumulative total P leaching (TPcum) tended to increase with increasing total and available P concentration in the soils. Among various compost properties, total P concentration was positively correlated with TPcum from the compost-amended soils, except for the Andisol, which has a high P-sorption capacity. There was no significant relationship between TPcum and water-extractable P concentration of the composts, suggesting that total P rather than inorganic P concentration of composts may be successfully used in predicting P leaching potential from compost-amended soils except for soils that have a high P-sorption capacity, as in Andisol.

Fly ash and zeolite amendments increase soil nutrient retention but decrease paddy rice growth in a low fertility soil

PurposeFly ash (FA) and zeolite (Z) are known to increase nutrient retention in paddy soils through the immobilization of phosphorus (P) by FA and nitrogen (N) by Z. However, there is a possibility that the co-application of the amendments may hamper rice growth due to reduced availability of the nutrients. This study was conducted to investigate the effects of the co-application of FA and Z on soil N and P availability and rice growth.Materials and methodsRice was cultivated in soils without the amendment (control) and with the amendment: FA alone, Z alone, and both FA and Z. Tiller number, dry matter (DM), rice uptake of N and P, and soil N and P concentrations were determined.Results and discussionThe application of FA and Z increased N and P concentrations in the soils; however, such increased nutrient retention did not translate to DM increases. Results suggested that reduced mobility of nutrients hampered tillering in the early growth period, eventually leading to a reduction in DM accumulation at the harvest. Due to the nutrient limitation caused by FA and Z, the rice grown with both FA and Z did not survive at the harvest.ConclusionsOur study shows that the application of FA and Z does not always improve rice growth due to nutrient limitation, especially in a low fertility soil. Furthermore, the co-application of FA and Z should be avoided, as the negative impact of FA or Z on nutrient limitation became more severe when FA and Z were co-amended.