Growth, yield and aerenchyma formation of sweet and multipurpose sorghum (Sorghum bicolor L. Moench) as affected by flooding at different growth stages

Abstract The greenhouse experiment was a 4 × 2 factorial in a RCB design with four replications. Three flooding treatments were applied at the early vegetative stage (EV), early reproductive stage (ER) and mid reproductive stage (MR). A non-flooded control group was used. Two proposed bioenergy sorghum types studied were sweet sorghum (Wray) and multipurpose sorghum (SP1). The results showed that plant height, stem diameter, leaf area, leaf dry weight, shoot dry weight, primary root length and root dry weight of both cultivars were significantly reduced by flooding at EV and ER. However, there was no significant difference from the control at MR. Nodal root number were restricted when flooding was applied at EV but increased over the control at ER and MR in both cultivars. Root length and root dry weight, developed in water above soil surface, were significantly higher in Wray flooded at ER. In both cultivars, aerenchyma spaces were formed in the nodal and lateral roots of the flooded plants with the significantly highest number, forming during EV. Aerenchyma was more developed in roots, located above the soil, than in those located in the soil. There were more aerenchyma spaces in the sweet sorghum's roots and stalk bases than in the multipurpose sorghum. At harvest, it was found that flooding applied at EV and ER had significantly reduced the stalk yield of both cultivars. The Wray had been the least affected by flooding at MR. These findings suggest that both sorghum types are susceptible to flooding at EV. Judging from the recovery capacity of stem diameter and height at a later growth stage, sweet sorghum was more tolerant to flooding than multipurpose sorghum. Nodal root development and aerenchyma formation in roots and stalk bases may be important acclimation responses to flooding

Increased arbuscular mycorrhizal fungal colonization reduces yield loss of rice (Oryza sativa L.) under drought

Drought reduces the availability of soil water and the mobility of nutrients, thereby limiting the growth and productivity of rice. Under drought, arbuscular mycorrhizal fungi (AMF) increase P uptake and sustain rice growth. However, we lack knowledge of how the AMF symbiosis contributes to drought tolerance of rice. In the greenhouse, we investigated mechanisms of AMF symbiosis that confer drought tolerance, such as enhanced nutrient uptake, stomatal conductance, chlorophyll fluorescence, and hormonal balance (abscisic acid (ABA) and indole acetic acid (IAA)). Two greenhouse pot experiments comprised three factors in a full factorial design with two AMF treatments (low- and high-AMF colonization), two water treatments (well-watered and drought), and three rice varieties. Soil water potential was maintained at 0 kPa in the well-watered treatment. In the drought treatment, we reduced soil water potential to − 40 kPa in experiment 1 (Expt 1) and to − 80 kPa in experiment 2 (Expt 2). Drought reduced shoot and root dry biomass and grain yield of rice in both experiments. The reduction of grain yield was less with higher AMF colonization. Plants with higher AMF colonization showed higher leaf P concentrations than plants with lower colonization in Expt 1, but not in Expt 2. Plants with higher AMF colonization exhibited higher stomatal conductance and chlorophyll fluorescence than plants with lower colonization, especially under drought. Drought increased the levels of ABA and IAA, and AMF colonization also resulted in higher levels of IAA. The results suggest both nutrient-driven and plant hormone-driven pathways through which AMF confer drought tolerance to rice

Introduction du haricot mongo (Vigna radiata L.) comme précédent cultural pour améliorer la disponibilité de l'azote et le rendement du riz pluvial dans le Nord Est de la Thaïlande

La revue Australian Journal of Agricultural Research devient en 2009 la revue Crop & Pasture Science (nouvel ISSN-L 1836-0947)International audienceOne possible management option for farmers to improve the soil nitrogen (N) supply for rice production is the cultivation of a prior legume. The objective of this study was to investigate the value of such an option in the lowland of the north-east of Thailand. Two experiments were established in 2 typical locations in a split-plot design with 4 replicates. The main plots included 3 nitrogen levels (0, 30, and 60 kg N/ha) and the subplots, 4 pre-rice managements: (i) fallow with weeds removed (FW–); (ii) with weeds incorporated before the rice crop (FW+); (iii) mungbean incorporated at .owering as green manure (MGM); or (iv) incorporated after grains harvest (MR+). In both experiments the difference in rice yield between MGMand MR+ was not significant. In Expt 1, in contrast to Expt 2, the rice yield increase due to MR+ was significant and significantly higher than that due to application of 60 kg N/ha. Moreover, significantly higher apparent recovery of N (ANRm, kg N uptake increase/kg N supplied by residues), probably due to the continuous .ooding of the soil surface, was achieved in this experiment. The low values of internal efficiency of N (IEN, kg total grains/kg total N uptake), ANRf (_kgNuptake/kg N supplied by fertiliser), and of ANUEf (_kg grains/kg applied N fertiliser) recorded in the MR+ treatment of Expt 1, suggest that no application of N fertiliser is needed where the soil water conditions allow high recovery of the N supplied by a preceding mungbean crop

Introducing mungbean as a preceding crop to enhance nitrogen uptake and yield of rainfed rice in the north-east of Thailand

One possible management option for farmers to improve the soil nitrogen (N) supply for rice production is the cultivation of a prior legume. The objective of this study was to investigate the value of such an option in the lowland of the north-east of Thailand. Two experiments were established in 2 typical locations in a split-plot design with 4 replicates. The main plots included 3 nitrogen levels (0, 30, and 60 kg N/ha) and the subplots, 4 pre-rice managements: (i) fallow with weeds removed (FW-); (ii) with weeds incorporated before the rice crop (FW+); (iii) mungbean incorporated at flowering as green manure (MGM); or (iv) incorporated after grains harvest (MR+). In both experiments the difference in rice yield between MGM and MR+ was not significant. In Expt 1, in contrast to Expt 2, the rice yield increase due to MR+ was significant and significantly higher than that due to application of 60 kg N/ha. Moreover, significantly higher apparent recovery of N (ANR(m), kg N uptake increase/kg N supplied by residues), probably due to the continuous flooding of the soil surface, was achieved in this experiment. The low values of internal efficiency of N (IEN, kg total grains/kg total N uptake), ANR(f) (Delta kg N uptake/kg N supplied by fertiliser), and of ANUE(f) (Delta kg grains/kg applied N fertiliser) recorded in the MR+ treatment of Expt 1, suggest that no application of N fertiliser is needed where the soil water conditions allow high recovery of the N supplied by a preceding mungbean crop