Iron Toxicity Tolerance of Rice Genotypes in Relation to Growth,Yield and Physiochemical Characters

Iron(Fe)toxicity,generated from excess reduced ferrous Fe(Fe^(2+))ion formation within the soil under submerged condition,is a potent environmental stress that limits lowland rice production.Total 11 diverse Thai rice genotypes,including a recognized tolerant genotype Azucena and a susceptible genotype IR64,were evaluated against 5 Fe^(2+)levels[0(control),150,300,600 and 900 mg/L]to screen the tested genotypes for their Fe-toxicity tolerance and to classify them as a sensitive/tolerant category.The evaluation was conducted by a germination study,followed by a polyhouse study on growth,yield and physiochemical performances.Results showed significant variations in Fe^(2+)-tolerance across genotypes.Increasing Fe^(2+)level beyond 300 mg/L was detrimental for germination and growth of all the tested genotypes,although germination responses were negatively affected at Fe^(2+)≥300 mg/L.Physiochemical responses in the form of leaf greenness,net photosynthetic rate,membrane stability index and Fe contents in leaf and root were the most representative of Fe^(2+)-toxicity-mediated impairments on overall growth and yield.Difference in physiochemical responses was effectively correlated with the contrasting ability of the genotypes on lowering excess Fe^(2+)in tissues.Analysis of average tolerance and stress tolerance index unveiled that the genotypes RD85 and RD31 were the closest to the tolerant check Azucena and the sensitive check IR64,respectively.The unweighted pair group method with arithmetic means clustering revealed three major clusters,with cluster Ⅱ(four genotypes)being Fe^(2+)tolerant and cluster Ⅰ(four genotypes)being Fe^(2+)sensitive.Principal component(PC)analysis and genotype by trait-biplot analysis showed that the first two components explained 90.5%of the total variation,with PC1 accounting for 56.6%and PC2 for 33.9%of the total variation.The identified tolerant rice genotypes show potentials for cultivation in Fe^(2+)-toxic lowlands for increased productivity.The findings contribute to the present understanding on Fe^(2+)-toxicity response and provide a basis for future genotype selection or rice crop improvement programs against Fe^(2+)-toxicity.

Effects of Silicon-Based Fertilizer on Growth, Yield and Nutrient Uptake of Rice in Tropical Zone of Vietnam

Application of silicon(Si) could greatly boost rice yield and mitigate abiotic stress,especially drought.A field experiment was conducted during 2015 at the research farm of Hong Duc University,Thanh Hoa City,Vietnam,to evaluate the effects of five different combined doses of standard fertilizer practice and Si fertilizer on growth,yield and yield components,as well as nutrient uptake of rice.The treatments consisted of the recommended dose of fertilizer(RDF,110 kg/hm^2 N + 90 kg/hm^2 P_2O_5 + 80 kg/hm^2 K_2O) as the control,RDF + 100 kg/hm^2 SiO_2,RDF + 200 kg/hm^2 SiO_2,RDF + 300 kg/hm^2 SiO_2 and RDF + 400 kg/hm^2 SiO_2.The results showed that the growth,grain and straw yields as well as yield components(number of grains per panicle,seed-setting rate and 1000-grain weight) were significantly affected by Si application.The highest grain yield of 3 705 kg/hm^2 was obtained with the highest level of Si fertilizer in combination with RDF(RDF + 400 kg/hm^2 SiO_2),however,it was statistically at par with the yields obtained with RDF + 300 kg/hm^2 SiO_2(3 664 kg/hm^2) and RDF + 200 kg/hm^2 SiO_2(3 621 kg/hm^2).The optimum dose of Si fertilizer with maximized grain yield(3 716 kg/hm^2) was 329 kg/hm^2 SiO_2.The nutrient(Si,N,P and K) uptakes of rice were also significantly enhanced by Si application.Si application at the level of 329 kg/hm^2 along with RDF would help in the sustainable production of rice in the tropical zone of Vietnam.

Integrated assessment of extreme climate and landuse change impact on sediment yield in a mountainous transboundary watershed of India and Pakistan

Assessment of climate and land use changes impact including extreme events on the sediment yield is vital for water and power stressed countries. Mangla Reservoir is the second-largest reservoir in Pakistan, and its capacity is being reduced due to rapid sedimentation and will be threatened under climate and land use changes. This paper discusses the consequences of climate and land use change on sediment yield at Mangla Dam using General Circulation Models(GCMs), Land Change Modeler(LCM), Soil and Water Assessment Tool(SWAT) model after calibration and validation.Results show that over the historical period temperature is observed to increase by 0.10 o C/decade and forest cover is observed to reduce to the level of only 16% in 2007. Nevertheless, owing to the forest conservation policy, the forest cover raised back to 27% in 2012. Anticipated land use maps by using LCM of 2025, 2050 and 2100 showed that the forest cover will be 33%, 39.2%, and, 53.7%, respectively. All seven GCMs projected the increase in temperature and five GCMs projected an increase in precipitation,however, two GCMs projected a decrease in precipitation. Owing to climate change, land use change and combined impact of climate and land use change on annual sediment yield(2011-2100) may vary from-42.9% to 39.4%, 0% to-27.3% and,-73%to 39.4%, respectively. Under climate change scenarios projected sediment yield is mainly linked with extreme events and is expected to increase with the increase in extreme events. Under land use change scenarios projected sediment yield is mainly linked with the forest cover and is expected to decrease with the increase in forest cover. The results of this study are beneficial for planners, watershed managers and policymakers to mitigate the impacts of climate and land use changes to enhance reservoir life by reducing the sediment yield.

Influence of preceding crop and tillage system on forage yield and quality of selected summer grass and legume forage crops under arid conditions

Among the crop production factors,preceding crop and tillage management affect the sustainable use of soil resources and ultimately crop growth and productivity.This study aimed at investigating the impact of preceding winter crops(grass or legume)and different tillage systems on forage yield,quality and nutritive values of three summer grass(Sudan grass,pearl millet and teosinte)and two legume forage crops(cowpea and guar)under arid conditions.The results exhibited that growing forage crops after legumes(as berseem clover)produced the highest fresh and dry forage yields and quality attributes compared with grasses(as wheat)with the exception of crude fiber content,which was decreased.Moreover,tillage practices showed positive impact on forage yields and quality attributes.The maximum forage yields and quality parameters were recorded under conventional tillage(CT)practice compared with reduced tillage(RT)and no-tillage(NT)systems.Among the evaluated crops,the highest yields of fresh forage,dry forage,crude fiber,crude protein and total digestible nutrient were exhibited by grass forage crops(Sudan grass,pearl millet and teosinte),whereas the highest crude protein content and the digestible energy values were produced by legume forage crops(cowpea and guar).The maximum fresh forage,dry forage,crude fiber,crude protein,total digestible nutrient and digestible crude protein yields were produced by pearl millet followed by Sudan grass under CT and RT after berseem clover.The highest net return was recorded by sowing pearl millet after berseem clover and applying CT followed by RT practices,which could be recommended for the commercial production.Moreover,it could be assumed that the combination of growing grass forage crops after legume crops under CT or RT systems could enhance forage crop yield and quality with an improvement in soil properties for sustainable agriculture with low cost and the highest net income.