Shading minimizes the effects of water deficit in Campomanesia xanthocarpa (Mart.) O. Berg seedlings

The objective of this study was to evaluate the activity of antioxidant enzymes, the functioning of the photosystem II and quality of C. xanthocarpa seedlings cultivated under intermittent water deficit and shading levels and the influence of shading on recovery potential after suspension of the stress conditions. The seedlings were subjected to three levels of shading (0, 30, and 70%), six periods of evaluation (start: 0 days; 1st and 2nd photosynthesis zero: 1st and 2nd P0; 1st and 2nd recovery: 1stand 2nd REC; and END), and two forms of irrigation (control: periodically irrigated to maintain 70% substrate water retention capacity, and intermittent irrigation: suspension of irrigation). The plants subjected to intermittent irrigation conditions at 0% shading showed a reduction in water potential (Ψw) and potential quantum efficiency of photosystem II (Fv/Fm) and maximum efficiency of the photochemical process (Fv/F0) and an increase in basal quantum production of the non-photochemical processes (F0/Fm). Superoxide dismutase (SOD) activity was higher in the leaves than in the roots. The C. xanthocarpa is a species sensitive to water deficit but presents strategies to adapt to an environment under temporary water restriction, which are more temporary are most efficient under shading. The seedlings with water deficit at all levels of shading exhibited higher protective antioxidant activity and lower quality at 0% shading. The shading minimizes prevents permanent damage to the photosystem II and after the re-irrigation, the evaluated characteristics showed recovery with respect to the control group, except POD and SOD activities in the leaves.

Risks for Using FeCl3 Under a Submerged Condition, and Different Water Management to Reduce Uptake of Antimony and Cadmium in a Rice Plant

Soil pollution by multiple metal(loid)s is a common problem, and it is not easy to synchronously reduce their uptake in crops. Compounds containing iron (Fe) are often used to efficiently remediate soil metal(loid) pollution; however, its associated risks did not receive much attention especially under unsuitable soil water conditions. Pot experiments were set up using an antimony (Sb) and cadmium (Cd) co-contaminated soil treated with a continued submergence condition plus 5, 10, or 20 mg kg−1 FeCl3 (Experiment I), or treated with different water management including submergence, intermittent irrigation, and dry farming (Experiment II). Our results showed that the continued submergence resulted in excessive accumulation of arsenic (As) in different tissues of rice plants even if the soil As background concentration is low. High soil moisture content increased the available concentrations of Sb and As, but reduced that of Cd in rhizosphere soils, which was in line with their concentrations in different tissues of rice plants (Experiment II). Under a continued submergence condition, FeCl3 significantly stimulated As concentration in the shoots, roots (excluded Fe20 treatment), and husks, but reduced it in the grains. FeCl3 reduced Sb concentration only in the roots and grains, and reduced Cd concentration only in the husks, suggesting a limited efficiency of FeCl3 to reduce Cd uptake under a submergence condition. In this study, the dynamic changes of As, Sb, and Cd concentrations in soil solution, their available concentrations in rhizosphere soils, their accumulation in root iron/manganese plaques, and the relationships among the above parameters were also discussed. We suggested that if FeCl3 would be used to remediate the contaminated soils by Sb and Cd, dry farming for a short time is needed to avoid As accumulation, and intermittent irrigation is a potential choice to avoid the excessive accumulation of As, Sb, and Cd in the edible parts of rice plants.

Effect of irrigation methods and testing some rice cultivars against growth, root development and yield on rainfed Ultisols of Aceh Besar

The main obstacle in rice cultivation on dryland is the limitation of water availability and large fluctuation of groundwater availability. It causes plant metabolic processes to be hampered. The threat of such natural conditions can be overcomed by intensifying and using superior cultivars to adapt widely to the environment, such as being resistant to drought. This study aims to determine the effect of irrigation methods and the response of several different cultivars to growth, yield potential, and rice root systems. This research using a Split Plot Design pattern. The factors examined in this study were irrigation methods, which consisted of 3 levels of treatment, namely continuous irrigation (P1), intermittent irrigation (P2), and sprinkler irrigation (P3). Variety factors consisted of 4 levels, namely: Batutegi (V1), Situ Patenggang (V2), Inpago 5 (V3), and Sanbei (V4), so there were 12 treatment combinations with three repetitions of 36 treatment plot units. The results showed that the continuous and intermittent irrigation methods gave the highest yield per hectare and had the same weight, while the sprinkler gave the lowest yield per hectare, although not significantly different from other irrigation methods. The cultivar that gave the highest yield per hectare was Sanbei, while the lowest was Situ Patenggang, and the cultivar that gave the highest 1000 grain weight was Inpago-5, while the lowest was Sanbei, although it was not significantly different from other cultivars.

How Do Different Nitrogen Application Levels and Irrigation Practices Impact Biological Nitrogen Fixation and its Distribution in Paddy System?

Background and aimsBiological nitrogen fixation (BNF) in paddy systems is impacted by nitrogen application levels and irrigation strategies, but the extents to which these factores influence BNF and its distribution in soil and rice were still largely unclear. This study investigates this influence.MethodsAn airtight transparent growth chamber 15N-labelling system were used to investigate how different nitrogen application levels (0, 125, 187.5 and 250 kg N ha-1) and irrigation strategies (flooding irrigation or intermittent irrigation) impact the amount of BNF and its distribution in soil and rice. ResultsNitrogen application at 125 ~ 250 kg N ha-1 reduced the amount of BNF by 81% - 86%. The inhibition effect of nitrogen application on BNF at a soil depth of 1-15 cm was greater than that at 0-1 cm. Relative to the continuous flooding irrigation, intermittent irrigation enhanced rice growth and promoted the transfer of fixed nitrogen from 0-1 cm soil layer to rice, but it did not change the total amount of BNF. ConclusionsThis study indicated that BNF supplied little nitrogen for rice production at the high nitrogen application levels, but the intermittent irrigation could promote utilization of biologically fixed nitrogen.

Influence of tillage practice on major pathways of CH4 emission in rice paddy field

<p> Generally, during the paddy rice cultivation period, CH<sub>4</sub> produced in the soil is reported to be released to the atmosphere through three pathways: diffusion (<1%), bubbles (<10%), and via rice (> 90%). However, there are few studies have measured gas diffusion coefficient for soil below surface of the water, and there is no study has provided an accurate understanding of CH<sub>4</sub> dynamics in paddy fields. Furthermore, there are few studies that understanding the CH<sub>4</sub> dynamics in fertilizer-free and pesticide-free paddy fields, which is mainly controlled by inter-tillage practices. Therefore, this study aimed to clarify the effects of tillage and the number of inter-tillage and the presence or absence of fertilizer and pesticide on the CH<sub>4</sub> dynamics in rice paddy soil. This study compared three types of CH<sub>4</sub> flux, which were total CH<sub>4</sub> flux from rice paddy field measured by transparent chamber with plants, and soil derived CH<sub>4</sub> flux measured by dark chamber without plants, and gas diffusion flux calculated as a product of the gas diffusion coefficient and measured soil gas concentration gradient at the depths of 0-5 and 5-10cm. And they were compared with in the five rice cultivation periods (flooding, mid-drying, intermittent irrigation, drainage, and fallowing) and in the four treatment plots (conventional farming (CF), and fertilizer- and pesticide-free farming with zero-inter-tillage(T0), two-inter-tillage(T2), and five-inter-tillage (T5)). The CF was conducted according to the regional recommendation for tillage, fertilization and pest and weed control. The results showed that the peak of total CH<sub>4</sub> flux was observed in the mid-drying and intermittent irrigation periods in all treatments, and that the CH<sub>4 </sub>flux via rice plant accounted for 60-90% of the total CH<sub>4</sub> flux. The CF showed significantly highest CH<sub>4</sub> emission during the periods, and the increase of the number of inter-tillage tended to increase the CH<sub>4</sub> emission. In the drainage period, the CH<sub>4</sub> flux by bubbles in the CF and T5 accounted for more than 80% of the total CH<sub>4</sub> flux. In the fallowing period, the diffusion CH<sub>4</sub> flux at the depth of 5-10cm increased in all treatments, but the low total CH<sub>4 </sub>emission and increased CO<sub>2</sub> emission. This study revealed that incorporation of organic matter into soil in conventional rice farming tended to increase CH<sub>4</sub> emission. The main pathway of CH<sub>4</sub> emission from rice paddy field was via rice, and it was influenced by tillage significantly. The decomposition of organic matter from rice straw and weeds incorporated into soil was the source of the bubble of CH<sub>4</sub>. Furthermore, it seemed that the most of diffusively transferred CH<sub>4</sub> was easily oxidized to CO<sub>2</sub>.</p>

Shading as a means of mitigating water deficit in seedlings of Campomanesia xanthocarpa (Mart.) O. Berg

In this research it was hypothesized that Campomanesia xanthocarpa can overcome some level of water deficiency by adjusting physiological parameters and that shading minimizes the water deficit effects while maintaining elevated photosynthetic rates and relative water content of the leaves and makes a resumption of metabolism and growth when the water supply is normalized. The seedlings were submitted to two water regimes (continuous irrigation - CI and intermittent irrigation - II), three shading percentages (0, 30 and 70%) and six evaluation times (Start - T0, 1st Photosynthesis Zero - 1st P0, 1st Recovery - 1st REC, 2nd Photosynthesis Zero - 2nd P0, 2nd Recovery - 2nd REC and END). Plants under water deficit at 0% shading led to a reduction in photosynthetic metabolism, relative water content (RWC), leaf area, number of leaves, and height, especially during the stress periods 1st and 2nd P0. The 30 and 70% shading mitigated the stressful effect of water deficit on C. xanthocarpa seedlings. The results did not confirm the hypothesis that C. xanthocarpa seedlings are intolerant to water deficit since, although sensitive, they presented a potential for recovery of photosynthetic and growth characteristics under all cultivation conditions. It was concluded that that shading minimizes the stressful effects of water deficit.