The underlying mechanism of variety–water–nitrogen–stubble damage interactions on yield formation in ratoon rice with low stubble height under mechanized harvesting

Agronomic measures are the key to promote the sustainable development of ratoon rice by reducing the damage from mechanical crushing to the residual stubble of the main crop, thereby mitigating the impact on axillary bud sprouting and yield formation in ratoon rice. This study used widely recommended conventional rice Jiafuzhan and hybrid rice Yongyou 2640 as the test materials to conduct a four-factor block design field experiment in a greenhouse of the experimental farm of Fujian Agricultural and Forestry University, China from 2018 to 2019.The treatments included fertilization and no fertilization, alternate wetting and drying irrigation and continuous water flooding irrigation, and plots with and without artificial crushing damage on the rice stubble. At the same time, a 13C stable isotope in-situ detection technology was used to fertilize the pot experiment. The results showed significant interactions among varieties, water management, nitrogen application and stubble status.Relative to the long-term water flooding treatment, the treatment with sequential application of nitrogen fertilizer coupled with moderate field drought for root-vigor and tiller promotion before and after harvesting of the main crop, significantly improved the effective tillers from low position nodes. This in turn increased the effective panicles per plant and grains per panicle by reducing the influence of artificial crushing damage on rice stubble and achieving a high yield of the regenerated rice. Furthermore, the partitioning of 13C assimilates to the residual stubble and its axillary buds were significantly improved at the mature stage of the main crop, while the translocation rate to roots and rhizosphere soil was reduced at the later growth stage of ratooning season rice. This was triggered by the metabolism of hormones and polyamines at the stem base regulated by the interaction of water and fertilizer at this time. We therefore suggest that to achieve a high yield of ratoon rice with low stubble height under mechanized harvesting, the timely application of nitrogen fertilizer is fundamental,coupled with moderate field drying for root-vigor preservation and tiller promotion before and after the mechanical harvesting of the main crop.

Acclimation and Tolerance Strategies of Rice under Drought Stress

Rice （Oryza sativa L.） is an important food crop and requires larger amount of water throughout its life cycle as compared to other crops. Hence, water related stress cause severe threat to rice production. Drought is a major challenge limiting rice production. It affects rice at morphological （reduced germination, plant height, plant biomass, number of tillers, various root and leaf traits）, physiological （reduced photosynthesis, transpiration, stomatal conductance, water use efficiency, relative water content, chlorophyll content, photosystem II activity, membrane stability, carbon isotope discrimination and abscisic acid content）, biochemical （accumulation of osmoprotectant like proline, sugars, polyamines and antioxidants） and molecular （altered expression of genes which encode transcription factors and defence related proteins） levels and thereby affects its yield. To facilitate the selection or development of drought tolerant rice varieties, a thorough understanding of the various mechanisms that govern the yield of rice under water stress condition is a prerequisite. Thus, this review is focused mainly on recent information about the effects of drought on rice, rice responses as well as adaptation mechanisms to drought stress.

Role of Organic Amendments to Mitigate Cd Toxicity and Its Assimilation in Triticum aestivum L.

In soil biota,higher and enduring concentration of heavy metals like cadmium(Cd)is hazardous and associated with great loss in growth,yield,and quality parameters of most of the crop plants.Recently,in-situ applications of eco-friendly stabilizing agents in the form of organic modifications have been utilized to mitigate the adverse effects of Cd-toxicity.This controlled experiment was laid down to appraise the imprints of various applied organic amendments namely poultry manure(PM),farmyard manure(FYM),and sugarcane press mud(PS)to immobilize Cd in polluted soil.Moreover,phytoavailability of Cd in wheat was also accessed under an alkaline environment.Results revealed that the addition of FYM(5–10 ton ha^(-1))in Cd-contaminated soil significantly increased germination rate,leaf chlorophyll content,plant height,spike length,biological and grain yield amongst all applied organic amendments.Moreover,the addition of FYM(5–10 ton ha^(-1))also reduced the phytoavailability of Cd by 73–85%in the roots,57–83%in the shoots,and 81–90%in grains of wheat crop.Thus,it is affirmed that incorporation of FYM(5–10 ton ha^(-1))performed better to enhance wheat growth and yield by remediating Cd.Thus,the application of FYM(5–10 ton ha^(-1))reduced the toxicity induced by Cd to plants by declining its uptake and translocation as compared to all other applied organic amendments to immobilize Cd under sandy alkaline polluted soil.

Laboratory-and Field-Phenotyping for Drought Stress Tolerance and Diversity Study in Lentil (Lens culinaris Medik.)

Drought susceptibility and low genetic variability are the major constraints of lentil(Lens culinaris Medik.)production worldwide.Development of an efficient pre-field drought phenotyping technique and identification of diversified drought tolerant lentil genotype(s)are therefore vital and necessary.Two separate experiments were conducted using thirty diverse lentil genotypes to isolate drought tolerant genotype(s)as well as to assess their diversity.In both of the experiments,significant(p≤0.01)variation in genotype(G),treatment(T)and G X T was observed for most of the studied traits.In experiment I,genotypes were examined for drought tolerance at the seedlings stage under hydroponic conditions by assessing root and shoot traits.Among the 30 genotypes studied,BM-1247,BM-1227 and BM-502 were selected as highly tolerant to drought stress as they showed maximum seedling survivability and minimum reduction in growth parameters under drought stress.In experiment II,the genotypes were assayed for diversity and drought stress tolerance based on morphological traits grown under field condition.Drought stress caused a substantial reduction in yield attributing traits,however,the genotypes BM-1247,BM-981,BM-1227 and BM-502 were categorized as drought tolerant genotypes with less than 20%yield reduction.The field screening result of drought stress tolerance was coincided well with the results of laboratory screening.Genetic divergence study reflected the presence of considerable diversity among the genotypes.Considering laboratory and field screening results,the genotypes,BM-1247,BM-1227,BM-981 and BM-502 were selected as the best drought tolerant genotypes.This information can be exploited for further breeding in developing drought tolerance in lentil.