Effects of planting time on growth, development and productivity of maize (Zea mays L.)

Planting date plays important role in the growth, development and yield of maize. Optimum planting date has becomes a prime importance for higher crop production. The plant establishment as well as pest and disease incidence are affected by planting dates. Crop varieties respond differently to planting dates. Early or late planting dates on maize causes an array of morpho-anatomical, physiological and biochemical changes in plants, which affect plant growth and development and such changes may lead to a drastic reduction in yield. Maize growth and development involves numerous biochemical reactions which are sensitive to variance in weather parameters as affected by planting dates. Delayed planting dates affect traits namely anthesis silking interval, photosynthesis, physiological maturity and dry matter production due to reduction in cumulative interception of photosynthetically active radiation (PAR). Late planting dates cause higher non-structural carbohydrate concentration in stems at mid-grain filling stages due to low temperature exposure of crop limiting kernel growth and photosynthesis. The adverse effects of delayed planting dates can be mitigated by forecasting optimum planting dates through crop modeling experiments. This article summarizes various effects of planting dates on maize growth, development and yield parameters. This information may be useful for maize growers and researchers

Performance evaluation of Barley (Hordeum vulgare L.) genotypes in Dolakha, Nepal: from yielding perspective

Lack of suitable barley varieties that exhibit high yielding is the major factor among several production constraints contributing to low productivity of barley in Nepal. The present study was done to evaluate and recommend the best performing barley genotypes. This study was conducted at research field of Hill Crops Research Program (HCRP), Dolakha, Nepal under National observation nursery (NON), initial evaluation trial (IET), coordinated varietal trials (CVT) and farmer's field trials (FFT) during winter seasons from 2017 to 2018. The results of these trials showed that in NON, genotypes namely B86023-1K2-OK3 (6.16 t/ha), Xveola-28/MATICO"S"10 (4.41 t/ha) and ACC#2079 (4.41 t/ha) produced higher grain yield over Farmer’s variety (3.57 t/ha). The pooled analysis over years of IET revealed that genotypes namely LG-51/Xveola-2-77-0-3-1-1-OK (2.12 t/ha) and B86099-2-1-OK (2.06t/ha) produced higher grain yield over standard check variety (Solu Uwa) (1.85 t/ha) and Farmer’s variety (1.95 t/ha). Similarly results of combined analysis over years of CVT showed that the genotypes namely B90K-007-0-2-2-0-OK (2.14 t/ha) and ICB90-0196-OAP-2K-OK (1.97 t/ha) produced higher grain yield over standard check variety (Solu Uwa) (1.12 t/ha) and Farmer’s variety (1.66 t/ha). In farmer's field trials (FFTs) the genotypes namely Muktinath ( Coll#112-14 (2.64 t/ha)), NB-1003-37/903 (2.23 t/ha) and Xveola-45 (2.04 t/ha) produced higher grain yield which was at par to standard check variety (Soluuwa) (1.58 t/ha) and Farmer’s variety (1.85 kg/ha). It is suggested that the superior genotypes derived from CFFT could be released and then recommended to farmers for general cultivation in Dolakha and similar other environments of Nepal

Evaluation of Heat Stress Tolerance Indices in Maize Inbred Lines

The heat stress during flowering, pollination and grain filling stages affect the productivity of maize. Twenty maize inbred lines were evaluated in field and plastic houses using alpha lattice design with two replications during spring season of 2016 at National Maize Research Program, Rampur, Chitwan, Nepal. Five stress tolerance indices namely stress susceptibility index (SSI), stress tolerance index (STI), tolerance index (TOL), geometric mean productivity (GMP) and mean productivity (MP) were applied to identify superior heat stress tolerant lines. The results showed that STI, SSI, GMP and MP indices were the more accurate criteria for selection of heat tolerant and high yielding lines. The positive and significant correlation of GMP and MP with grain yield under both conditions revealed that these two indices were more applicable and efficient for selection of inbred lines. The biplot analysis identified the groups of tolerant and sensitive inbred lines. The maize inbred lines namely RL-140 and RML-91 found high yielding and low stress susceptibility in both conditions. These results suggest that the inbred lines namely RL-140 and RML-91 should be use a source of heat tolerance for maize breeding program

Evaluation of white grain maize varieties for growth, yield and yield components

Maize (Zea mays L.)  is one of the most commonly cultivated crop after rice in Nepal. The present study was done to evaluate and recommend the best performing white maize genotypes in mid hill region of Nepal. This study was conducted at research field of Kavre, Nepal during the rainy season of 2019. Five white maize genotypes were evaluated in randomized complete block design with four replications where Deuti used as standard check. Ear and plant height of plant, days to 50% silking and tasseling, count of leaf above and below main cob, total number of leaf, cob length, cob diameter, kernel rows per cob, kernels count per row, thousand kernels weight, shelling and sterility percentage, stay green and grain yield parameters were observed. Deuti and DMH-7314 had good stay green and husk cover rating. Plant height (282.6 cm) and ear height (162.4 cm) was more in HB-008. Number of kernels per row was more in HB-008 (36.5) and HB-007 (36.5) and thousand kernel weights was more in DMH-7314 (386.3 g) followed by Deuti (353.9 g). DMH-7314 was late in tasseling (86 days) and silking (89 days) but shelling percentage was lowest in DMH-7314 (70.8) than other varieties. Analysis of variance reveled that genotype HB-008 (9.70 t/ha) as compared to standard check Deuti (7.80 t/ha). Thus genotype HB-008 perform better in mid hill region of Kavre, Nepal

Mechanisms of heat stress tolerance in maize

High temperature has become a global concern because it severely affects the growth and production of crops. It causes an array of morpho-anatomical, physiological and biochemical changes in plants, which affect plant growth and development and may lead to a drastic reduction in economic yield. Plant growth and development involve numerous biochemical reactions that are sensitive to temperature. Heat stress causes an abrupt increase in the expression of stress-associated proteins which provide tolerance by stimulating the defense response in plants. Plants possess a number of mechanisms to cope with high temperature situations. The adverse effects of heat stress can be mitigated by developing crop plants with improved thermotolerance using various genetic approaches. This article reviews the recent information on responses and tolerance to high temperature stress in maize

Grain Yield Stability of Rice Genotypes

Stability analysis identifies the adaptation of a crop genotype in different environments. The objective of this study was to evaluate promising rice genotypes for yield stability at different mid-hill environments of Nepal. The multilocation trials were conducted in 2017 and 2018 at three locations viz Lumle, Kaski; Pakhribas, Dhankuta; and Kabre, Dolakha. Seven rice genotypes namely NR11115-B-B-31-3, NR11139-B-B-B-13-3, NR10676-B-5-3, NR11011-B-B-B-B-29, NR11105-B-B-27, 08FAN10, and Khumal-4 were evaluated in each location. The experiment was laid out in a randomized complete block design with three replications. The rice genotype NR10676-B-5-3 produced the highest grain yield (6.72 t/ha) among all genotypes. The growing environmental factors (climate and soil conditions) affect the grain yield performance of rice genotypes. The variation in climatic factors greatly contributed to the variation in grain yield. Polygon view of genotypic main effect plus genotype-by-environment interaction (GGE) biplot showed that the genotypes NR10676-B-53 and NR11105-B-B-27 were suitable for Lumle; NR11115-B-B-31-3 and NR11139-B-B-B-13-3 for Pakhribas; and 08FAN10 and NR11011-B-B-B-B-29 for Kabre. The GGE biplot showed that genotype NR10676-B-5-3 was stable hence it was near to the point of ideal genotype. This study suggests that NR10676-B-5-3 can be grown for higher grain yield production in mid-hills of Nepal

Nitrogen uptake and economics of black rice (Oryza sativa L. indica) under different crop geometries and nitrogen management practices

Black rice has more antioxidants than any other rice variety.  It is considered to have multiple benefits in human health due to the presence of different antioxidants. A field experiment was conducted during rainy season of 2015-2016 to assess the nitrogen uptake, use efficiency and economics of black rice production under different crop geometry and nitrogen (N) management practices in Rampur, Chitwan, Nepal. The experiment was laid out in strip plot design with three replications. The experiment consisted of  treatment combination of three crop geometry (20 cm × 20 cm, 20 cm × 15 cm and 15 cm × 15 cm) in vertical plots and three nitrogen management practices (N level: 30 kg N ha-1, 60 kg N ha-1, and LCC based N-management) in horizontal plots. The results showed that the highest N uptake was recorded from closer spacing (15 cm × 15 cm) with LCC based N management. The net return and B: C ratios were higher at a closer spacing of 15 cm × 15 cm with LCC based N management and closer spacing of 15 cm × 15 cm with N application of 60 kg ha-1. The overall analysis revealed that LCC based N management under closer crop geometry (15 cm × 15 cm) was the best management practices because of high nitrogen uptake and highest monetary return with B: C ratio of 5.76

Role of nutrients in rice (Oryza sativa L.): A review

Nutrients are important for plant growth and development. In this review, previous works were evaluated to investigate the role of nutrients, nutrient deficiency and toxicity in rice. Both macro and micronutrients are necessary for rice plants. Every nutrient has its own character and is involved in different metabolic processes of plant life. Nutrients affect the disease tolerance or resistance of plants to pathogens. Nutrient deficiency and toxicity conditions inhibit normal plant growth and exhibit characteristic symptoms. For optimal growth, development, and production, plants need all the necessary nutrients in balance. Integrated nutrient management in rice has many benefits to increase soil fertility and sustainable crop productivity. The information of this review article would be useful to rice growers and researchers for sustainable and higher rice productio

Impact of adoption of heat-stress tolerant maize hybrid on yield and profitability: Evidence from Terai region of Nepal

Abiotic stresses (drought, heat) are one of the major impediments to enhancing the maize productivity of marginal farmers in the facet of climate change. The present study attempts to investigate the impact of heat-tolerant maize hybrid on yield and income in the Terai region of Nepal. This study uses cross-sectional farm household-level data collected in August 2021 from a randomly selected sample of 404 rural households. We used a doubly robust inverse probability weighted regression adjustment method to obtain reliable impact estimates. Adoption of heat-tolerant hybrid increases yields by 16% and income by 44% in the spring season (a stress condition). Overall, yield increases by 12%, net income by 31%, saving of 40% in seed costs, and per capita food expenditure increases by 8.50%. Hence a conducive environment must be created for scaling up heat-tolerant maize varieties to increase productivity, minimize risk, and transform of the maize sector

Global age-sex-specific mortality, life expectancy, and population estimates in 204 countries and territories and 811 subnational locations, 1950–2021, and the impact of the COVID-19 pandemic: a comprehensive demographic analysis for the Global Burden of Disease Study 2021

Background: Estimates of demographic metrics are crucial to assess levels and trends of population health outcomes. The profound impact of the COVID-19 pandemic on populations worldwide has underscored the need for timely estimates to understand this unprecedented event within the context of long-term population health trends. The Global Burden of Diseases, Injuries, and Risk Factors Study (GBD) 2021 provides new demographic estimates for 204 countries and territories and 811 additional subnational locations from 1950 to 2021, with a particular emphasis on changes in mortality and life expectancy that occurred during the 2020–21 COVID-19 pandemic period. Methods: 22 223 data sources from vital registration, sample registration, surveys, censuses, and other sources were used to estimate mortality, with a subset of these sources used exclusively to estimate excess mortality due to the COVID-19 pandemic. 2026 data sources were used for population estimation. Additional sources were used to estimate migration; the effects of the HIV epidemic; and demographic discontinuities due to conflicts, famines, natural disasters, and pandemics, which are used as inputs for estimating mortality and population. Spatiotemporal Gaussian process regression (ST-GPR) was used to generate under-5 mortality rates, which synthesised 30 763 location-years of vital registration and sample registration data, 1365 surveys and censuses, and 80 other sources. ST-GPR was also used to estimate adult mortality (between ages 15 and 59 years) based on information from 31 642 location-years of vital registration and sample registration data, 355 surveys and censuses, and 24 other sources. Estimates of child and adult mortality rates were then used to generate life tables with a relational model life table system. For countries with large HIV epidemics, life tables were adjusted using independent estimates of HIV-specific mortality generated via an epidemiological analysis of HIV prevalence surveys, antenatal clinic serosurveillance, and other data sources. Excess mortality due to the COVID-19 pandemic in 2020 and 2021 was determined by subtracting observed all-cause mortality (adjusted for late registration and mortality anomalies) from the mortality expected in the absence of the pandemic. Expected mortality was calculated based on historical trends using an ensemble of models. In location-years where all-cause mortality data were unavailable, we estimated excess mortality rates using a regression model with covariates pertaining to the pandemic. Population size was computed using a Bayesian hierarchical cohort component model. Life expectancy was calculated using age-specific mortality rates and standard demographic methods. Uncertainty intervals (UIs) were calculated for every metric using the 25th and 975th ordered values from a 1000-draw posterior distribution. Findings: Global all-cause mortality followed two distinct patterns over the study period: age-standardised mortality rates declined between 1950 and 2019 (a 62·8% [95% UI 60·5–65·1] decline), and increased during the COVID-19 pandemic period (2020–21; 5·1% [0·9–9·6] increase). In contrast with the overall reverse in mortality trends during the pandemic period, child mortality continued to decline, with 4·66 million (3·98–5·50) global deaths in children younger than 5 years in 2021 compared with 5·21 million (4·50–6·01) in 2019. An estimated 131 million (126–137) people died globally from all causes in 2020 and 2021 combined, of which 15·9 million (14·7–17·2) were due to the COVID-19 pandemic (measured by excess mortality, which includes deaths directly due to SARS-CoV-2 infection and those indirectly due to other social, economic, or behavioural changes associated with the pandemic). Excess mortality rates exceeded 150 deaths per 100 000 population during at least one year of the pandemic in 80 countries and territories, whereas 20 nations had a negative excess mortality rate in 2020 or 2021, indicating that all-cause mortality in these countries was lower during the pandemic than expected based on historical trends. Between 1950 and 2021, global life expectancy at birth increased by 22·7 years (20·8–24·8), from 49·0 years (46·7–51·3) to 71·7 years (70·9–72·5). Global life expectancy at birth declined by 1·6 years (1·0–2·2) between 2019 and 2021, reversing historical trends. An increase in life expectancy was only observed in 32 (15·7%) of 204 countries and territories between 2019 and 2021. The global population reached 7·89 billion (7·67–8·13) people in 2021, by which time 56 of 204 countries and territories had peaked and subsequently populations have declined. The largest proportion of population growth between 2020 and 2021 was in sub-Saharan Africa (39·5% [28·4–52·7]) and south Asia (26·3% [9·0–44·7]). From 2000 to 2021, the ratio of the population aged 65 years and older to the population aged younger than 15 years increased in 188 (92·2%) of 204 nations. Interpretation: Global adult mortality rates markedly increased during the COVID-19 pandemic in 2020 and 2021, reversing past decreasing trends, while child mortality rates continued to decline, albeit more slowly than in earlier years. Although COVID-19 had a substantial impact on many demographic indicators during the first 2 years of the pandemic, overall global health progress over the 72 years evaluated has been profound, with considerable improvements in mortality and life expectancy. Additionally, we observed a deceleration of global population growth since 2017, despite steady or increasing growth in lower-income countries, combined with a continued global shift of population age structures towards older ages. These demographic changes will likely present future challenges to health systems, economies, and societies. The comprehensive demographic estimates reported here will enable researchers, policy makers, health practitioners, and other key stakeholders to better understand and address the profound changes that have occurred in the global health landscape following the first 2 years of the COVID-19 pandemic, and longer-term trends beyond the pandemic