Category Archives: Wiley: Journal of Agronomy and Crop Science

Cover crop water consumption: Analysing performance of the agrometeorological model for the calculation of actual evapotranspiration (AMBAV) in a container experiment

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Due to anthropogenic climate change, cover crop water consumption in winter could potentially increase drought stress for a succeeding crop. Simulation of cover crop evapotranspiration (ET) losses could be a tool for farmers to make smart management decisions. In Germany, the model AMBAV is used by the German Meteorological Service (DWD) to advise farmers in irrigation management. We compared measured ET of phacelia (Phacelia tanacetifolia), oilseed radish (Raphanus sativus var. oleiformis) and white mustard (Sinapis alba) cultivated in a container experiment with simulated data and conducted a sensitivity analysis to identify the meteorological and crop-specific parameters, which had the strongest effect on simulated ET. In general, measured ET exceeded simulated ET. Different statistical criteria showed that AMBAV performed best for the simulation of evaporation from a bare soil surface. Model performance was also strongly influenced by the irrigation regime in the container experiment. However, the sensitivity analysis showed that changes in irrigation hardly influenced simulated ET. We recommend optimization of the model for irrigated agriculture. Furthermore, we identified temperature and humidity as the most important meteorological and leaf area index as the most important crop-specific parameter for ET simulations with AMBAV. Since farmers' management decisions depend on the accuracy of ET simulations, they should be aware that even small regional deviations of meteorological conditions and soil cover can significantly affect model predictions.

Current status of global rice water use efficiency and water‐saving irrigation technology recommendations

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Rice has a high water requirement, but water use efficiency (WUE) in rice has always been low, and the status of rice WUE and the factors influencing it in various countries around the world is currently unclear. Therefore, this paper collected 56 articles from 2000 to 2022, through which WUE data from different countries and different provinces in China were collated, and the effects of various water-saving irrigation technologies on WUE of rice and irrigation water use were analysed using the method of Meta-analysis. The results of this paper show that rice WUE is low in most countries, with the lowest WUE of 0.28 kg/m3 in Thailand and the highest WUE of 1.25 kg/m3 in Bangladesh among the countries included in this study, and flood irrigation is used in most countries. Compared to flood irrigation, all water-saving irrigation involved can increase rice WUE and reduce irrigation water input, alternate wet and dry irrigation (W1), and controlled irrigation (W2) were able to increase the WUE of rice by 49.86%, 84.74%, and reduce the irrigation water input by 36.55%, 39.55% respectively. Among the six types of water-saving irrigation input, dry cultivation (W3) had the most significant effect on increasing WUE and reducing irrigation water, reaching 2.02 times and 67.53%, respectively. Based on the annual rainfall (R) and the application of water-saving irrigation in Asia, sub-regionally applicable water-saving irrigation technologies are recommended. W3 is recommended when R <200 mm, W2 is recommended when 200 mm < R < 800 mm, and W1/W2/shallow alternate wet and dry irrigation (W5) is recommended when R >800 mm. According to the data collected in this paper, W1, W2, W3, and W5 can save 3.40 × 1011 m3, 3.78 × 1011 m3, 2.52 × 108 m3, 2.22 × 1011 m3 of irrigation water, respectively. Based on the calculations in this paper, different water-saving irrigation techniques can save 3.50 × 1011 m3 of water in Asia according to the recommendations. To promote water-saving irrigation technology, countries need to formulate policies to ensure the development of water-saving irrigation technology, raise farmers' awareness of water conservation, and provide training and financial support. Promoting the use of different water-saving irrigation technologies for different regions can significantly reduce irrigation water and increase the WUE of rice, which is important in addressing the challenges of global water scarcity.

Transmission of photosynthetically active radiation and the productivities of soybean and maize in agroforestry systems

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In integrated crop-livestock-forestry (ICLF) systems, an agroforestry model, the forestry component influences the distribution of photosynthetically active radiation (PAR) and alters grain productivity. The aim of this study was to evaluate the effects of systematic and selective thinning of eucalyptus stands on the productivity of soybean and maize grown. The randomized block-designed experiment comprised three treatments, namely crops grown under full sunlight (CFS) and in ICLF plots subjected to systematic and selective thinning to leave single-row (ICLFS) and triple-row (ICLFT) tree configurations. Soybean and maize were planted in succession between the tree stands and PAR incidence/transmittance and crop productivities were evaluated in the north and south sun-exposed faces of the plots during three cultivation cycles after thinning. In comparison with CFS, PAR transmittance in the ICLF systems decrease varied according to the time of day, period of the year, distance of the sampling position from the trees, the sun-exposed area (north and south faces) and time after thinning. Soybean productivities in ICLFS were similar to those of CFS in the first and second crop cycles, but significantly lower (p < 0.05) in the third crop cycle. In the ICLFT system, soybean productivity was similar to that of CFS in the second crop cycle but significantly lower in the first and third crop cycles. With regard to the maize crop, productivities decreased in the order CSF > ICLFS > ICLFT in all cultivation cycles. Our results showed that PAR transmittance and soybean/maize productivities were positively influenced by thinning of eucalyptus stands, particularly in ICLFS system.

Plant photosynthetic responses under drought stress: Effects and management

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Balanced photosynthesis is essential for improved plant survival and agricultural benefits in terms of biomass and yield. Photosynthesis is the hub of energy metabolism in plants; however, drought stress (DS) strongly perturbs photosynthetic efficiency due to biochemical and diffusive limitations that reduce key photosynthetic components and close stomata. This review describes photosynthetic responses, chloroplast retrograde signalling, and genetic imprints that curtail DS damage to photosynthetic machinery. While stomatal closure, disrupted photosynthetic systems, over-reduced electron transport rates (ETR), partial hindrance of the Calvin cycle, and reduced pigment contents strongly affect the repertoire of photosynthetic processes under DS, chloroplast retrograde signalling also has a plausible role in preserving photosynthetic capacity. Progress in agronomic, genetic engineering approaches and isoprene regulation would help to rescue photosynthetic apparatus under DS.

Screening of barley germplasm for drought tolerance based on root architecture, agronomic traits and identification of novel allelic variants of HVA1

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Drought is a major constraint for barley production as it is normally cultivated in rainfed and marginal areas lacking optimum productivity. The domestication bottleneck and further selection pressure have resulted in reduced genetic diversity in barley. Genebank germplasm holds a huge potential for identifying new alleles for stress tolerance. In the present study, a diverse set of 214 accessions from Indian National Genebank were screened for drought tolerance in hydroponics and field conditions. Analysis of variance revealed a significant effect of drought on root architecture, relative water content, membrane stability index, chlorophyll content, plant height, and yield attributes. Cumulative stress response in terms of better root phenotype, physiological and agronomic traits showed accessions IC113045, EC578521, IC582699, EC492318, EC578711, EC667420, IC393980 and IC594943 as most promising donors for breeding programmes in drought-prone areas. Further allelic variation of candidate gene, Hordeum vulgare aleurone 1 (HVA1), and its promoter sequence was studied in a subset of drought-tolerant and -susceptible accessions. The HVA1 gene showed six SNPs and one indel in the genic regions whereas three SNPs and one indel in promoter. Two alleles of HVA1 gene, one in exotic and other in indigenous accession, were found to be associated with drought tolerance. These results were confirmed by qRT-PCR analysis exhibiting significant increase in transcript abundance of HVA1 in drought-tolerant accessions in comparison with susceptible accessions, thereby highlighting its possible role in imparting drought tolerance. The study helped identify genetic resources for drought tolerance in barley and unravelled new alleles of HVA1.

Classification of soybean genotypes during the seedling stage in controlled drought and salt stress environments using the decision tree algorithm

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Soybean is one of the most important oilseed crops grown worldwide. However, abiotic stresses such as drought and salinity can seriously affect soybean production, especially in tropical climate conditions. To evaluate the adaptability and stability of soybean genotypes under abiotic stress conditions, some studies have proposed a multitrait tool to select stress-tolerant soybean genotypes through a multitrait stability index (MTSI). This index can be used under stressful environmental conditions to quantify the genotypic stability of soybean cultivars. Our study is based on an unprecedented approach, where we propose to use a machine learning algorithm called ‘Random Forest’ to obtain a classification model based on a decision tree algorithm. The decision tree data structure can be used even by nonexperts facilitating the decision-making process for genotype selection. The proposed model evaluated the importance of six shoot and root morphological variables and predicted from which controlled growth environment the soybean plants originated. Using this model more than 73% of the genotypic patterns were learned correctly. Besides that, this model can also predict and rank the most critical variables in the development of soybean genotypes, having obtained results very similar to recent field research. The research is important for plant breeders who seek an early selection of soybean seedlings for drought and saline stresses.

Relationship between characteristics of basal internodes and lodging and its physiological mechanism in direct‐seeded rice

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Lodging is an important factor that limits rice yield and the large-scale promotion of direct-seeded rice (DSR). The objective of this study was to clarify the relationship between the characteristics of basal internodes and lodging and the physiological mechanism underlying this process in DSR. A field study was conducted in Changchun, Jilin Province, China, using a japonica rice variety Jiyujing with two direct seeding cultivation methods, including dry DSR (DDSR), wet DSR (WDSR) and conventional-transplanted rice (CTSR) as a control in 2019 and 2020. Lodging-related physical parameters, morphological characteristics and carbohydrate components of basal internodes were investigated at heading stage (HS) and 30 days after heading stage (HS30). The results showed that WDSR increased lodging index (LI) and lodging rate compared with CTSR and DDSR. LI increased rapidly from HS to HS30, primarily because of the significant reduction in the breaking strength (M). Correlation analysis revealed that the M of N4 internode was significantly positively correlated with culm plumpness and structural carbohydrate proportions at HS30. Culm plumpness decreased significantly, due to a decrease in nonstructural carbohydrate (NSC) content then primarily the decrease in starch proportions and content. Compared with CTSR and DDSR, WDSR decreased culm wall thickness, dry weight per centimetre of the culm and leaf sheaths, and the proportions and contents of cellulose, lignin and starch of internode, resulting in the decrease in internode breaking strength. Thus, it was concluded that the DSR reduced internode strength by reducing internode plumpness and carbohydrate content, thus decreasing lodging resistance.

Saline stress affects the growth of Saccharum complex genotypes

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Soil salinity affects plant growth, compromising sugarcane cultivation in regions with great production potential. Saccharum complex genotypes that respond positively to growth under saline environment can be used in the diversification of sugarcane cultivars to obtain greater economic returns. The objective of this study was to evaluate growth-related traits of Saccharum genotypes grown under the presence and absence of salinity. The experiment was carried out in a 32 × 2 factorial scheme in a randomized block design with three replicates. The first factor consisted of 32 genotypes of the Saccharum complex and the second factor consisted of the presence and absence of salinity. The salinity provided higher mean values than the environment without salinity for plant height in the genotypes G9, G11, G13, G22 and G28, leaf number for G9 and G24, leaf area index for G9 and stem diameter for G1, G11 and G24. Among the genotypes tested, G1, G9, G11, G13, G22, G24 and G28 were the most promising genotypes and could be used for breeding new sugarcane cultivars of enhanced salinity tolerance.

Does the plant growth regulator paclobutrazol enhance root growth of maize exposed to drought stress during flowering?

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Due to climate change, crop production will increasingly be affected by water limitation, causing remarkable decreases in grain yields of cereals. Plant growth regulators such as paclobutrazol (PAC) have been shown to protect plants from detrimental impacts of drought stress, and improvement of root growth and antioxidant activity were identified as main reasons for their positive effect. A container experiment was conducted with two maize (Zea mays L.) cultivars, Galactus and Fabregas, to investigate how PAC application affects root growth and grain yield under stress conditions. At growth stage V8, the plants were treated once with PAC (0, 2, or 3 mg PAC per plant), and concomitantly reduction in soil water content commenced until 30–35% of the maximum water-holding capacity (WHC) was achieved. The plants were exposed to this drought condition for three weeks during flowering as the critical period for kernel setting. Both factors, PAC application and drought stress, caused decreases in plant height, whereas total leaf area was unchanged and transpiration rate was significantly reduced by water limitation only. Flowering was almost unaffected by PAC treatment; yet, drought stress significantly delayed start of silking. The straw yield was decreased due to PAC and drought stress, and an improvement of the harvest index was obtained for drought-stressed Galactus plants with PAC application. Grain yield was unaffected by PAC application, whereas drought stress caused significant decreases by 15% on average of both cultivars. The kernel number of drought-stressed Galactus plants was increased after PAC treatment, but concurrently smaller kernels were produced. Water limitation generally decreased kernel number. Drought-stressed Fabregas plants consumed less water after PAC treatment, resulting in significant improvements of water-use efficiency (WUEgrain) during silking and thus most likely alleviating stress intensity. For both cultivars, PAC treatment and water limitation showed almost no significant impact on root dry matter, root length density, and root surface area, either determined for different soil layers down to 80 cm or on a per-plant basis. It is concluded that grain yield performance of maize plants, exposed to water limitation during flowering, was not source-limited but sink-limited. Consequently, even if PAC can cause improvement of antioxidant activity and photosynthesis, due to sufficient availability of assimilates in the maize kernels a positive effect on grain yield is improbable. Considering source–sink relationships during flowering and kernel set, enhanced root growth due to PAC treatment did apparently not occur.

Determination of low‐temperature stress during the vegetative stage as a tool to predict plant yield in rice genotypes with contrasting tolerance levels

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In this study, the first aim was to develop a rapid and non-destructive method for analysing rice genotypes' tolerance to low temperatures (LT) during the seedling stage. Using a growth parameter and a physiological parameter, a discriminant formula was developed to differentiate between tolerant and sensitive genotypes based on their LT tolerance score. The study identified several benefits of the discriminant formula, including its low classification error rate, scalability, and ability to be used in controlled and reduced environments. Additionally, a second study was conducted, which found a strong correlation between the LT tolerance score during the seedling stage and plant yield at the ripening stage in plants grown under field LT during the vegetative stage. Panicle weight was the main mediator of the effect of the LT tolerance score on plant yield, but the number of panicles per plant also played a role. Overall, the results suggest that the LT tolerance score can serve as an indirect selection factor for plants for both LT tolerance and plant yield. This is especially relevant for rice-growing regions with temperate climates and LT at the beginning of the cultivation season.