Tiller Mortality Research Articles

Source-sink relationships during early crop development influence earliness of sugar accumulation in sugarcane.

In subtropical environments where sugarcane (Saccharum spp.) crops are frequently limited by the duration of the growth cycle, earliness in maturity is a key genotypic trait. Using the concept of source-sink relationships, we hypothesised that earliness is controlled by the dynamics of tillering (DT), which define sink strength early in the growth cycle. Five modern commercial sugarcane genotypes with similar sucrose yields and varying degrees of earliness in ripening were grown in the field over three years and their DT, dynamics of sucrose accumulation (DS), and source-sink relationships over time were characterised. Canonical correlations and principal components analysis revealed that DT explained 68% of the total variance in DS. Early ripening genotypes exhibited the shortest thermal time to the end of tiller mortality (θTilmort), the lowest tiller survival and millable tiller number, and greatest sugar content at θTilmort (Sconc,Tilmort). The rate and duration of the sucrose accumulation phase did not explain the genotypic variation either in final sugar content or in earliness when considered in isolation without taking into account the effect of Sconc,Tilmort. In the set of genotypes examined, the variation in final sucrose yield was most explained by the variation in stalk number. We conclude that the dynamics of tiller appearance and senescence modified the early source-sink relationships and thus determined the differential sucrose contents around θTilmort and the earliness of maximal sugar accumulation. θTilmort, which was closely associated with the 14-leaf phenological stage, emerged as a candidate trait to screen for genotypic variation in early ripening, crop cycle duration, and yield.

Tillering dynamics of digit grass subjected to different defoliation frequencies

Abstract: The objective of this work was to evaluate the tillering dynamics of 'Suvernola' digit grass (Digitaria eriantha) when subjected to different defoliation frequencies. Four defoliation frequencies (interval among harvests) were evaluated - very high, when the grass reached 25 cm in height; high, 35 cm; medium, 45 cm; and low, 55 cm - in two seasons of the year, with higher and lower insolation, from January 2015 to January 2016. A randomized complete block design with four replicates was used. The increase in defoliation frequency increased the number of generations and the appearance, mortality, and density rates of tillers, besides decreasing their survival rate, without changing population stability. At the time of lower insolation, tiller appearance and mortality rates were higher, while tiller survival rate, balance, and density were lower. The evaluated defoliation frequencies and seasons of the year do not change the persistence of digit grass when irrigated. Higher defoliation frequencies result in a greater renewal of digit grass tillers.

Experimental evidence that the perennial grass persistence pathway is linked to plant growth strategy.

Grass species can be classified into different functional types based on their growth strategies, and contrasting persistence strategies are observed in different grass species. Excluding seedling recruitments, changes in populations of grasses are basically a trade-off between natality and mortality of tillers. We hypothesised that the persistence pathway of perennial grasses is linked to their growth strategy, regardless whether they are growing as monoculture or as a mixture. Species with contrasting growth strategies (Arrhenatherum elatius L., Dactylis glomerata L., and Festuca arundinacea Schreb.) were cultivated as monocultures and as a mixture and their tiller natality and mortality were evaluated for two years after swards establishment. All pastures maintained their population size during the experimental period, although decreases in tiller densities occurred during the warmer season. Arrhenatherum elatius had the highest tiller mortality and natality whereas the F. arundinacea had the lowest ones. Arrhenatherum elatius had many tillers appearing in all seasons but their tillers were short-lived. Conversely, F. arundinacea and D. glomerata developed numerous tillers during autumn and winter and their tillers survived, on average, almost six and three times longer than those of A. elatius, respectively. There were no differences in tillering dynamics among populations grown in monocultures or in the mixture. Regardless of whether they were cultivated in monocultures or as a mixture, the persistence pathway of perennial grasses is linked with their growth strategies with exploitative species presenting a high tiller turnover throughout the year whereas the persistence of more conservative species is based on a high tiller survival.

Marandu palisade grass management strategies at the beginning of the deferment period and effects on tillering

Pasture mowing at the beginning of deferment stimulates tillering and can be used in different ways. The aim of this study was to understand how the mowing of Urochloa brizantha cv. Marandu Syn. Brachiaria brizantha cv. Marandu (marandu palisade grass) prior to the deferment period modifies tillering activity and the characteristics of young, mature, and old tillers. Three mowing strategies were evaluated: canopies kept at a height of 15 cm for five months before deferment (15/15 cm); canopies kept at 30 cm (30/15 cm) or 45 cm (45/15 cm) for five months before deferment and posteriorly cut to 15 cm at the start of the deferment period. The structural characteristics of young, mature, and old tillers of marandu palisade grass were compared only at the end of the deferment period. The tiller appearance rate was greater before (16.0%) than during (6.4%) the deferment period, but a contrasting response pattern was observed for the tiller mortality rate. The defoliation strategies that resulted in greater numbers of tillers in the canopies were 30/15 cm (2,098 tillers m-²) and 45/15 cm (2,160 tillers m-2). The defoliation strategy that generated the greatest percentage of young tillers in the canopy was 45/15 cm (26.1%), while the percentage of old tillers was greater in the canopies submitted to the 15/15 cm (64.1%) and 30/15 cm (61.5%) strategies. Weight and percentage of live stems of mature and old tillers were greater in relation to young tillers. The percentage of live leaves was grater in young tillers (52.6%), intermediate in mature tillers (41.4%), and lower in old tillers (21.3%). Regarding the percentage of dead leaves, the opposite trend was observed, where the percentage was greater in the old than in young tillers. Leaf area was greater in mature tillers (55.3 cm²) than in old tillers (29.2 cm²). Mowing of the marandu palisade grass to 15 cm at the beginning of the deferment period increases the number of young tillers, which have a more favorable morphological composition than mature and old tillers.

Tolerance of Different Winter Wheat Cultivars to Prolonged Freezing Injury at their Critical Temperatures

Inconsistent survival during winter due to freezing injury of varying severity is a major impediment to winter wheat (Triticum aestivum L.) growth and productivity. To evaluate the tolerance of different winter wheat cultivars and different organs of the same cultivar to prolonged freezing injury, 3 yr of controlled freezing experiments were performed with four cultivars under different freezing durations at the cultivars’ corresponding critical temperatures. Experimental plants in plastic pots that have hardened in the field were moved to freezing chambers for controlled freezing treatments during the winter. A highly significant relationship was observed between freezing duration and mortality for each of the different cultivars and organs. For every 1‐d increase in freezing duration at the critical temperature, plant mortality increased by 8.6, 22.3, 11.1, and 9.4% for cultivars Jing411, Nongda211, Zhengmai366, and Yanzhan4110, respectively. Within the same cultivar, tillers (15–32% d−1) were less sensitive to freezing duration than younger leaves (25–35% d−1) and older leaves (20–55% d−1). Spike number was greatly influenced by freezing duration and the resulting death of tillers. For every 1% increase in tiller mortality, spike number per pot declined by 1.3, 2.0, 1.2, and 0.7% for cultivars Jing411, Nongda211, Zhengmai366, and Yanzhan4110, respectively. These findings indicate that reducing tiller death during winter is important for preventing extensive decreases in spike number.

Effect of freezing temperature and duration on winter survival and grain yield of winter wheat

Climate change has already increased the occurrence of extreme temperature events, which has restricted the production and development of winter wheat. To evaluate the effects of freezing temperature and duration on winter wheat survival and grain yield, two years of controlled freezing experiments were conducted under different freezing temperatures and durations. Three freezing temperatures (T1, T2 and T3) were implemented in these experiments, and soil minimum temperatures of −14 °C, −17 °C and −20 °C were designated for T1, T2 and T3, respectively. The freezing durations were designed as 2, 4, 6, 8 and 10 days under T1, 1, 2, 3, 5, 6, 7, 8 and 9 days under T2, and 1, 2, 3, 4, 5, 6 and 8 days under T3. The effects of freezing duration on the mortality of plants and tillers, as well as its effects on the grain yield per pot (GYPP), were much more serious under lower temperature. For every 1-day increase in freezing duration, GYPP decreased by 3.3% and 8.4% under T1 and T2, respectively, while the spike number per pot (SNPP) decreased by 4.4% and 21.6% under T1 and T2, respectively. When analyzing the combined effects of freezing temperature and duration, we introduced freezing degree days (FDD), which uses soil minimum temperatures below a threshold of −12 °C to represent the magnitude of the exposure to freezing temperature and duration. For every 1 °C·d increase in FDD, the mortality of plants and tillers increased by 1.0% and 1.4%, respectively. The interaction between freezing temperature and duration had a great effect on GYPP (0.5–1.2%/oC·d), while SNPP was more sensitive to freezing stress than GYPP and decreased at a rate of 2.3–2.9%/oC·d. An increasing trend in grain number per spike (GNPS) was clearly observed as FDD increased in 2014–2015, while freezing stress during the overwintering period had no direct influence on thousand-grain weight (TGW). The variation in GYPP was mainly caused by the grain number per pot (GNPP = SNPP × GNPS). The contribution of SNPP to the variation in GYPP was greater than that of GNPS or TGW under mild temperature, while GNPS contributed more under severe temperature. The results of this study provide data support for the improvement of crop models when simulating the effect of temperature stress on grain crops, and they can be consulted to predict freezing injury during winter wheat production.

CHANGES IN TILLERING DYNAMICS OF INTERCROPPED BLACK OAT AND ANNUAL RYEGRASS ENSURE A STABLE SWARD

SUMMARYMixing species with different tillering peaks may enhance pasture stability, but intercropping may also alter the plants’ tillering patterns. This study aimed to evaluate tillering dynamics in black oat (Avena strigosa Schreb.) and annual ryegrass (Lolium multiflorum Lam.) pastures grown as monocultures or intercropped. Three following treatments are established: black oat and annual ryegrass pastures grown as monocultures and an intercrop composed of these two species. Tillering dynamics were measured for black oat and annual ryegrass populations separately. When intercropped, tiller birth rates of black oat decreased (20.0 vs. 28.9 tillers 100 tillers−1) and those of annual ryegrass increased (30.5 vs. 14.3 tillers 100 tillers−1), compared to their monocultures. Tiller death rates for annual ryegrass did not differ between monoculture and intercropping (23.9 tillers 100 tillers−1), but black oat presented higher mortality in monocultures (48.8 vs. 36.4 tillers 100 tillers−1). The black oat monoculture had the lowest population stability index (0.80), whereas annual ryegrass in monoculture and intercropped pastures exhibited greater values (on average, 0.92). Our results indicated that black oat and annual ryegrass present distinct tillering dynamics whether grown as monoculture or intercropped, and suggest that intercropping species with elevated death rates (black oat) with later species (annual ryegrass) could be an important tool for maintaining pasture stability throughout the growing season.

Duration of developmental phases, and dynamics of leaf appearance and tillering, as affected by source and doses of photoperiod insensitivity alleles in wheat under field conditions

Variation in photoperiod sensitivity in wheat plays a major role in the crop adaptation to wide agronomic environments. Photoperiod insensitivity is provided by Ppd-Aa, Ppd-B1a and Ppd-D1a alleles. Effects of the genome, doses and source of the particular Ppd-1a alleles on time to anthesis has not been analysed simultaneously in the same experiments, even less under field conditions; and the effects on particular phases rather than on considering only the total time to anthesis and on phyllochron have not been considered for this range of allele combinations. We carried out field experiments during two consecutive growing seasons to assess differences in time to anthesis, in its component phases, in final leaf number, phyllochron and tillering across wheat isogenic lines differing in specific Ppd alleles and homoeoalleles. In addition to confirming that the introgression of Ppd-1a alleles advanced anthesis time (on average by 307, 251 and 191°C d if there were 3, 2 or 1 insensitivity alleles introgressed, respectively), we found that the variation between photoperiod insensitive genotypes was largely dependent on the varietal source of Ppd-B1a which could be stronger or weaker than Ppd-D1a depending on the donor considered. All components of time to flowering: the particular sub-phases (P<0.001) as well final leaf number (P<0.001) and phyllochron of late-appearing leaves (P<0.05) were sensitive to Ppd-1a alleles, but the strength of particular alleles on particular components was different, so that similar adjustments in time to anthesis could be achieved with different partitioning of developmental time between the considered phases. We also found that although they did not affect phyllochron of the first 7 leaves, that of the leaves appearing later was consistently reduced in lines carrying Ppd-1a. Tillering was sensitive too, but not final number of spikes due to compensations between tillering and tiller mortality.

Tiller density and tillering on Brachiaria brizantha cv. Marandu pastures inoculated with Azospirillum brasilense

ABSTRACT The objective of this study is to verify the population density and the dynamics of tillering in the Marandu palisade grass sward subjected to nitrogen (N) fertilization strategies, characterized by the N supply via urea or bacterial inoculant (Azospirillum brasilense). The treatments comprised of four nitrogen fertilization strategies: (A) Without fertilization, (B) 80 kg N/ha, (C) inoculant (A. brasilense), and (D) 80 kg N/ha + inoculant, distributed in a randomized complete block design, with three replications. The nitrogen supply strategies were evaluated during six periods: October, November, and December (2012) as well as January, March, and April (2013). The nitrogen dose or inoculant had no effect on the tiller appearance rate (TAR), tiller mortality rate (TMR), tiller survival rate (TSR), or tiller population density (TPD). However, these variables were influenced by the season. The TAR and TSR were higher at the beginning of the experimental period (October) and lower towards the end of the period (March-April), whereas, TMR and TPD exhibited the opposite behavior, with lower values in October and higher from January onward. Neither the nitrogen nor the inoculant influenced the population dynamics of the tillers in Marandu palisade grass.

Vernalisation and photoperiod sensitivity in wheat: Impact on canopy development and yield components

Genetic variation in the VERNALIZATION1 (VRN1) and PHOTOPERIOD1 (PPD1) genes, which control the vernalisation and photoperiod response, underpin wheat adaptation to different environments. Near isogenic lines were used to investigate the role of allelic combinations of VRN1 and PPD-D1, including new alleles for VRN1-A1, on the length of developmental phases, dynamics of leaf and tiller appearance and yield components in complementary irrigated field trials relevant to low latitude wheat growing areas and controlled conditions. Allelic differences in VRN1 had a stronger effect on the duration of the vegetative phase, while photoperiod sensitivity at PPD-D1 lengthened the stem elongation phase (SE) by up to 23%. If a phase was lengthened, flowering was delayed. The level of response to daylength during stem elongation (SE) introduced by photoperiod sensitive alleles was dependent on the VRN1 composition and vernalisation status. A longer SE under short days was achieved by PPD1 sensitive genotypes when one VRN1 spring allele was present and plants were vernalised. The duration of SE was weakly related to spike dry weight m−2 at DC65 in the field but did not translate into higher grain number m−2. In the field, lines with two to three VRN1 spring alleles had shortest development phases, including SE, close flowering dates, sampled similar temperature environments at different stages, and achieved high yields. Yield advantage was explained by higher biomass, harvest index, grain number m−2 and thousand kernel weight. Genotypes with three winter VRN1 alleles were comparatively disadvantaged, with a longer vegetative phase placing SE under higher temperatures. Allelic differences in both genes caused large variation in leaf and tiller number generation but also in tiller mortality and individual leaf size, lessening the impact on leaf area. Changes in plant morphology and yield components that did not seem mediated via the influence of development genes on the duration of different stages and their impact on resource capture deserve further investigation.

Effect of Herbicide Dose and Water Management on Weed Control Efficiency and Yield Performance of Boro Rice

An experiment was conducted at the Experimental Farm of the Bangabandhu Sheikh Mujibur Rahman Agricultural University (BSMRAU), Salna, Gazipur during November 2011 to May 2012 to determine the effect of pre-emergence herbicide Pretilachlor @ 75%, 100%, 125%, 150%, 175% and 200% of the recommended dose under two water management regime i.e. continuous flooding and field capacity on weed suppression and yield performance of Boro rice cv. BRRIdhan28. One weed free and one control (unweeded) treatment were also imposed for treatment comparison. The experiment was laid down in Split Plot design with three replications. Standard management practices for transplanted rice were followed. Continuous flooding was found to contribute better weed control efficiency than field capacity. At 60 DAT, the highest weed control efficiency of 65.75% was found in the treatment receiving Pretilachlor @ 125% of the recommended dose under continuous flooding and the least (54.76%) was found in the treatment receiving 75% of the recommended dose under field capacity. Continuous flooding contributed to more tillers thanfield capacity, and herbicide up to 125% of the recommended dose enhanced tillering in rice. At 75DAT the highest number of tillers (17.53 hill-1) were found in the plots receiving Pretilachlor @ 125% of the recommended dose under good water management (W1T3), while the lowest (11.10 hill-1) was recorded in W2T6 treatment receiving Pretilachlor @ 200% of the recommended dose under field capacity. The highest tiller mortality (27.90%) was observed in W1T3 treatment, whereas the least (8.06%) was observed in W2T5 treatment receiving the same herbicide @175% of the recommended dose under field capacity. Application of Pretilachlor at recommended dose under continuous flooding contributed to the highest crop dry matter production (1144.60g m-2) thus leading to the highest grain yield of 6.31 t ha-1 being followed by the treatment receiving Pretilachlor @ 125% of the recommended dose under same water management yielding 5.95 t ha-1 along with the highest harvest index of 0.58. Results revealed that Pretilachlor at recommended dose might be considered as viable option for weed management in transplanted Boro rice cultivation for effective weed management and satisfactory grain yield provided that appropriate water management is adopted. Journal of Science Foundation 2014;12(2):39-46DOI: http://dx.doi.org/10.3329/jsf.v12i2.27737

Compensatory phenotypic plasticity in irrigated rice: Sequential formation of yield components and simulation with SAMARA model

High-yielding rice varieties (HYV) show strong compensation among sequentially developed yield components (YC). This phenotypic plasticity has adaptive value but for crop improvement, more information is needed on its effects on yield. SAMARA, a deterministic crop model predicting trait-trait and trait-environment interactions by simulating morphogenetic processes and competition among sinks for assimilates, was developed to study crop phenotypic plasticity. Dynamics of YC and morphology were observed on the HYV IR72 planted at standard and 4-fold greater density in 4 environments in the Philippines in 2012/13. Data for other years/seasons were obtained for model validation. Sequential path analysis was used to determine the phenotypic plasticity of traits consecutively contributing to yield. Tiller number at flowering (R2=0.94) and maturity (R2=0.84) and grain yield (R2=0.77) were predicted accurately for independent datasets. The model also predicted accurately density effects on aboveground dry weight (agdw), plant height, leaf size, spikelet number per panicle and filling percentage. Tiller and leaf mortality were over-estimated under high density. Overall, the model predicted satisfactorily the sequential compensation processes among YCs. They led to stable grain yield despite large morphological differences among density treatments and environments. Sensitivity analysis of simulation outcomes vs. variation in crop parameters indicated that modified genotypic tillering ability, phyllochron or leaf size had little effect on final grain yield because of compensations by other traits, although IR72 appeared to have an optimal combination of parameter values. Larger effects on grain yield were predicted for variation of parameters affecting the sensitivity of leaf and tiller mortality to assimilate resources and the ability to mobilize stem non-structural carbohydrates during grain filling. The model will be used next to perform physiological trait dissection and plasticity analyses for diverse genotypes.

Proper supply of S increases GSH synthesis in the establishment and reduces tiller mortality during the regrowth of Tanzania guinea grass used for Cd phytoextraction

Cadmium has caused serious environmental problems due to its phytotoxicity, requiring solutions to reduce its concentration in the environment. Because S can alleviate the phytotoxicity caused by heavy metals, the evaluation of the effects of S supply is a promising approach to address this problem. The aim of this study was to determine the influence of S in reducing the phytotoxicity caused by Cd to Panicum maximum Jacq. cv. Tanzania (guinea grass) and to evaluate the potential of this grass for Cd phytoextraction. Tanzania guinea grass was cultivated in a nutrient solution to evaluate the combinations of five rates of S (0.1, 1.0, 1.9, 2.8, and 3.7 mmol L−1) and five rates of Cd (0.0, 0.5, 1.0, 1.5, and 2.0 mmol L−1), in a 52 fractional factorial design with six replications. Six plants were grown per pot in two growth periods to evaluate the effect of Cd on the establishment (51 days of age) and on the regrowth (18 days of growth) of the plants. During regrowth, Cd was not supplied in the nutrient solution. At the end of each growth period, growth parameters, concentrations of S and Cd, Cd transport factor, and concentrations of hydrogen peroxide (H2O2), malondialdehyde, reduced glutathione, and oxidized glutathione were evaluated. On the establishment of Tanzania guinea grass, application of Cd reduced mass production by 39 % due to the increases in the concentration of Cd (30 times compared with the treatment without Cd) and in lipid peroxidation (124 %). During regrowth, the residual effect of Cd resulted in a lower number of tillers (62 %) and leaves (89 %) caused by the increase in concentrations of Cd, H2O2 (49 %), and lipid peroxidation, which resulted in a 65 % lower dry mass production. The proper supply of S reduced concentration of Cd and tiller mortality rate due to the residual effect of Cd on the regrowth of the grass. Mass production by the roots was 43 % lower because of Cd, but the transport of Cd from roots to shoots increased. The increase in the concentration of glutathione (GSH) associated with a possible higher activity of antioxidant enzymes alleviated the phytotoxic effects of Cd on the guinea grass. The supply of S reduces the phytotoxicity caused by Cd to guinea grass, especially during the regrowth of the plant, when the concentration of Cd is higher because of the transport from roots to shoots. Tanzania guinea grass showed to be very promising for phytoextraction of Cd due to its high mass production, even when Cd was largely available in the nutrient solution.

Tillering dynamic and structural characteristics of tropical grasses under cutting management

This paper aimed to evaluate the dynamics of tillering, tiller density and structural characteristics of Brachiaria brizantha , Panicum maximum and Cenchrus ciliaris under a cutting regime. The utilized design was randomized blocks with six treatments (cultivars) and three replications. The evaluations were conducted from May to September 2011, with the data grouped into two periods, rainy season and beginning of the dry season. The greatest tiller population density was observed in the Massai cultivar, averaging 1,019 tillers.m -2 . The tiller mortality rate was higher for Mombaca and less for Piata cultivars. The highest values for forage mass, percentage of leaf blades and relations between green mass:dead mass were observed in Brachiaria brizantha and Panicum maximum cultivars. Panicum and Brachiaria cultivars have shown to be promising for cultivation in the transition areas between the Atlantic Forest and Caatinga biomes in Northeastern Brazil. Cenchrus cultivars are less productive in environments without restriction of abiotic factors.

Tillering dynamics in massai grass fertilized with nitrogen and grazed by sheep

To evaluate the tillering dynamics of massai grass under rotational sheep stocking and fertilized with nitrogen (control - 0; 400; 800 and 1200 kg ha -1 year -1 ), this study was carried out, in a completely randomized design with repeated measures over time. The mob-grazing technique was applied to perform the grazing by employing groups of animals for rapid defoliation. The tiller appearance, survival and mortality rates, tiller biomass, and green/dead tillers ratio, have presented increase responses to nitrogen levels, with the three rates and the tiller biomass varying between evaluation periods. There was a quadratic response for the tiller flowering rate, population density of vegetative and reproductive tillers, reaching maximum values (0.051 tiller 100 tiller -1 day -1 ; 4,818 and 35 tillers m -2 , respectively) under the nitrogen levels of 613.5; 993.5 and 623.9 kg ha -1 year -1 , respectively. For the tiller flowering rate and population density of reproductive tillers, it was verified a fluctuation between periods. The nitrogen fertilization promotes positive changes in tillering dynamics of massai grass, allowing the use of up to 800 kg ha -1 year -1 for maintaining the pasture stability. The tillering demography of the forage had varied little between assessment periods.

Submergence Induced Tiller Mortality and Yield Reduction in Rice Can be Minimized Through Post-submergence Nitrogen Application

The main strategies enabling rice plants to cope up with flash flooding stress require growth regulation during submergence and subsequent rapid growth recovery after de-submergence and better nutrient management options can enhance this strategy. Application methods of nitrogen and phosphorus were evaluated in submerged rice for tiller mortality, productivity, grain quality and nutrient absorption. The performance of Sub1 (IR-64 Sub1 and Swarna Sub1) and non-Sub1 (IR-20) cultivars of rice was tested under clear and turbid water for their tolerance to submergence in response to basal phosphorus and post-submergence nitrogen. Tillering ability, yield and nutrient absorption of rice subjected to complete submergence for 15 days was decreased significantly over non-submerged rice plants. Turbid water submergence was fatal in terms of tiller mortality, reduced nutrient absorption and yield because of low light and dissolved oxygen underwater. The crop fertilized with nitrogen produced more number of tillers, yield attributes and grain yield than the unfertilized crop under complete submergence at maximum tillering stage, effects were more positive when basal phosphorus was applied with nitrogen. Urea foliar spray after desubmergence significantly enhanced the leaf area, dry matter weight, specific leaf weight, tiller regeneration ability and narrowed down the flowering time which led to higher grain yield and productivity. The findings of the study suggest that higher rice yield can be obtained by adjustment in timing of nutrient application in flood prone areas, where farmers are scared to apply fertilizer because of risk involved.

Manure Limits Wheat Yield Losses Due to Delayed Seeding

Grain yields can be limited from delayed seeding worldwide. Perhaps yield suppressions can be overcome by applying farm manure. The objective of this study was to determine the influence of manure application and sowing date on wheat (Triticum aestivum L.) yield and population development. A field experiment was conducted over two seasons, with three sowing dates (early [ES]‐ 5 October; mid [M]‐ 10 October; late [LS]‐ 15 October) with or without manure application (each plot receiving same chemical N, P, and K fertilizer) in the North China Plain (NCP). Comparing early to LS, delayed sowing reduced wheat yield from 9.5 to 7.8 t ha−1. Furthermore, manure application provided a 16 and 11% yield compensation for the M and LS date treatments, respectively, but did not significantly increase yield for ES. These results were attributed to manure increasing the wheat pre‐winter tiller numbers for the mid‐seeding date and manure increasing the spring tiller numbers for the LS date. High tiller mortality rate of ES treatment with manure application resulted in similar spike number and wheat yield as no manure treatment. Manure application improved plant N, P, and K concentration and soil temperature at a depth of 5 cm (0.4°C for pre‐winter and 0.5–0.8°C for post‐stem elongation), actions that may be important for improving population development.

Impact of cyclic water stress on growth, physiological responses and yield of rice (Oryza sativa L.) grown in tropical environment

A series of water stress cycles [5, 10, 15, 20, 25 and 30 days of irrigation intervel including control flooded (CF), control saturated (CS)] were exposed to investigate the impact of cyclic water stress on growth, physiological responses and yield of a famous Malaysian rice variety, MR220. The study also aimed to determine optimum irrigation schedule for better production of rice. It was observed that grain yield, total biomass, filled spikelet, 1000 grain weight, total panicle, tillers mortality, plant height and number of tillers per plant reduces with increased duration of water stress cycles. Grain yield was higher both in CF and CS condition and those are statistically identical to 5 days of stress cycle or irrigation intervel. The present experiment shows that growth performance and physiological activities of rice differ marginally for 5 days of irrigation difference, exceding that time would reduce yield significantly. The study also showed that proline accumulation and malondialdehyde (MDA) contents in levels increased with increasing duration of water stress cycle. Depending on the findings of the present, it can be stated that rice variety MR220 do not require flooding irrigation and irrigation cycle of 5 days interval is more apprapriate to increase water use and higher yield of rice

Effect of Extended Water Stress on Growth, Tiller Mortality and Nutrient Recovery Under System of Rice Intensification

System of rice intensification was initially introduced to increase rice productivity in India, but is recently popularized as promising water saving practice. Sustaining rice productivity with minimal use of water is the need of the day. In this background, an experiment was designed to assess the effect of variable degrees of water stress namely no-stress, mild-stress and prolonged-stress imposed throughout the crop growth by scheduling irrigation at 1, 3 and 5 days, respectively after disappearance of ponded water under system of rice intensification with two different planting geometry and two contrasting varieties. Results clearly demonstrated that mild and prolonged stress during late vegetative stage (45–75 days after transplanting) greatly (P ≤ 0.05) enhanced (30.3–41.5 %) crop growth rate while, any level of stress during reproductive phase reduced (8.8–10.8 %) the rate of crop growth. Despite of higher tiller production under stress condition, large number of tillers failed to convert in ear-bearing tillers indicating higher tiller mortality under stress environment. Meanwhile, tiller density was not confirmed as a yield determinant while, the rice yield had higher correlation with grain weight panicle−1 (r = 0.743*), filled grain percentage (r = 0.806*), test weight (r = 0.683*) and nutrient uptake. With increase in stress intensity, apparent recovery of nutrients significantly (P ≤ 0.05) reduced, and the decline rate was in the order of potassium > phosphorus > nitrogen. Rice crop imposed mild-stress maintained at par yield (P > 0.05) with no stress, however prolonged-stress resulted in significant yield loss. Thus, mild-stress throughout the crop growth can reduce the water requirement and would be an effective water management strategy under water limited conditions.

Sugarcane tolerance to ratoon eradication with glyphosate determined by physiological responses

This study aimed to evaluate the tolerance of sugarcane cultivars to ratoon eradication under different glyphosate rates by means of physiological responses. Therefore, a trial was carried out in randomized complete blocks with 4 x 4 factorial design (cultivars x rates) totaling 16 treatments with four replicates. The cultivars IAC91-5155, IACSP93-3046, and IAC86-2480 and IAC87-3396 and the glyphosate rates 0 g ha-1; 1,920 g ha-1; 2,400 g ha-1; 2,880 g ha-1 were tested. The variables analyzed were percentage of tiller mortality, quantum efficiency of PSII (Fv/Fm) and SPAD index. The results showed that there are differences among sugarcane cultivars for tiller eradication and for physiological responses with glyphosate different rates. The rate of 2,880 g ha-1 was the most efficient in eliminating sugarcane tillers. The cultivars IAC86-2480, IAC87-3396 and IACSP93-3046 were the most sensitive and the IAC91-5155 tolerated, for a longer period of time, the damage to the photosynthetic apparatus of the ratoons caused by glyphosate desiccation. Due to different responses, different managements should be considered for eliminating ratoons of different cultivars.