Research Article
Long-term warming altered soil physical structure and soil organic carbon pools in wheatland field
- Rentian Ma, Taiji Kou, Xianghan Cheng, Ning Yu
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- Published online by Cambridge University Press:
- 03 January 2024, e1
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The impacts of long-term warming on soil physical structure and soil organic carbon (SOC) pools are currently disputed and uncertain. We conducted an eleven-year warming experiment in wheatland field in Henan, China. We found that long-term warming significantly increased soil bulk density by 4.5%, and significantly decreased total porosity and non-capillary porosity by 3.4% and 5.0%, respectively. Besides, long-term warming decreased the >2 mm fraction proportion and increased <0.053 mm fraction proportion of dry and wet aggregates. The mean weight diameter value for dry and wet aggregates in long-term warming treatment was significantly decreased by 7.0% and 6.7%, respectively. Moreover, long-term warming significantly decreased the total SOC, very labile pool (F1) and labile pool (F2) content by 10.6%, 30.6%, and 43.6%, and significantly increased the less labile pool (F3) and non-labile pool (F4) content by 94.2% and 21.1%, respectively. Long-term warming increased the passive carbon pool percentage but decreased the active carbon pool (ACP) percentage. Our results suggest that long-term warming negatively affected the soil's physical structure and impaired soil ACP accumulation. The findings of this study help improve our understanding of the response of farmland soils in northern China to climate change and provide scientific basis for establishing carbon management measures in farmland.
The temperature optima for pollen germination and pollen tube growth of coconut (Cocos nucifera L.) strongly depend on the growth temperature
- Dushan P. Kumarathunge, Lasantha K. Weerasinghe, Ruwan K. Samarasinghe, Nalaka Geekiyanage
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- Published online by Cambridge University Press:
- 08 January 2024, e2
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Understanding trait variation in response to temperature is important to predict how crops respond to rising temperature. Although we have a sound understanding of the effects of increasing temperature on growth and development of crops, a robust assessment of how crop reproductive processes are affected by climate warming is still lacking. In this study, we experimentally investigate how the growth temperature affects the cardinal temperatures of in vitro pollen germination of widely distributed tree crop species Cocos nucifera L. (cultivar Sri Lankan Tall). We hypothesize that temperature optima for pollen germination and pollen tube growth would be determined by the growth temperature. Our results showed that the temperature optima of pollen germination and pollen tube growth were higher at relatively warmer sites (sites where the mean annual temperature ∼ 28°C) compared to the cooler sites (sites where the mean annual temperature ∼ 22°C). The two processes were better coordinated at warmer sites. We speculate that tropical tree species that are currently growing in relatively cooler environments may have the capacity to perform their reproductive physiological functions in future warmer climates without any substantial negative impacts. Findings of this study should prove useful in quantifying the potential impacts of climate warming on tropical agro-ecosystems, improving the representation of plant reproduction in crop models.
Multi-trait selection for agronomic performance and drought tolerance among durum wheat genotypes evaluated under rainfed and irrigated environments
- Reza Mohammadi, Mahdi Geravandi
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- 24 January 2024, e3
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Durum wheat (Triticum turgidum L. subsp. durum) is a major crop in the Mediterranean region, widely grown for its nutritional value and economic importance. Durum wheat breeding can contribute to global food security through the introduction of new cultivars exhibiting drought tolerance and higher yield potential in the Mediterranean environments. In this study, 25 durum wheat genotypes (23 elite breeding lines and two national checks) were evaluated for five drought-adaptive traits (days to heading, days to maturity, plant height, 1000-kernel weight and grain yield) and eight drought tolerance indices including stress tolerance index (STI), geometric mean productivity (GMP), mean productivity (MP), stress susceptibility index, tolerance index, yield index, yield stability index and drought response index under rainfed and irrigated conditions during three cropping seasons (2019–2022). Multi-trait stability index (MTSI) technique was applied to select genotypes with higher grain yield, 1000-kernel weight, plant stature and early flowering and maturity simultaneously; as well as for higher drought tolerance in each and across years. A heat map correlation analysis and principal component analysis were applied to study the relationships among drought tolerance indices and the pattern of variation among genotypes studied. Factor analysis was applied for identification of traits that contributed most in stability analyses. Significant and positive correlations were observed among the three drought tolerance indices of STI, GMP and MP with mean yields under both rainfed and irrigated conditions in each and across years, suggest the efficiency of these indices as selection criteria for improved drought tolerance and yield performance in durum wheat. The genotypes ranked based on MTSI varied from environment to environment, showing the impact of environment on genotypes performance, but several of the best performing lines were common across environments. According to MTSI for agronomic traits, the breeding lines G20, G6, G25 and G18 exhibited highest performance and trait stability across environmental conditions, and the selected genotypes had strength towards grain yield, 1000-kernel weight and earliness. Using the MTSI, breeding lines G20, G5, G16 and G7 were selected as drought tolerant genotypes with high mean performance. Breeding line G20 from ICARDA germplasm showed highest trait stability performance and drought tolerance across environments. The MTSI was a useful tool for selecting genotypes based on their agronomic performance and drought tolerance that could be exploited for identification and selection of elite genotypes with desired multi-traits. Based on the results, breeding lines G20 and G6 should be recommended for short-term release programme and/ or utilized in durum wheat population improvement programme for agronomic performance and drought tolerance traits that tolerate climate variations.
Selenium accumulation in grains of wheat cultivars grown in selenium-rich areas in China
- Weilin Kong, Hafeez Noor, Aixia Ren, Linghong Li, Pengcheng Ding, Yongkang Ren, Zhiqiang Gao, Min Sun
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- 30 January 2024, e4
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Selenium (Se) is an essential micronutrient for human health, and Se concentration of wheat grain in China has no significant relationships with selenium concentration of wheat and with soil organic matter, nitrogen, phosphorus, potassium in the 0–20 cm soil layer. However, a significant indigenous positive correlation was found with soil Se concentration. Field experiments were conducted from 2018 to 2020 to clarify the differences in the Se accumulation in wheat plants grown in Se-rich areas. We used two common wheat (ZM-175, SN-20), two purple wheat (JZ-496, ZM-8555), and two black wheat (YH-161, LH-131) cultivars to investigate changes in Se build-up and transportation in plant organs. The grain Se concentration of six wheat genotypes in Se-rich areas varied between 178 and 179 μg Se kg−1, with organic Se accounting for 87 to 91%. All genotypes had more than 150 μg Se kg−1, the standard Se concentration in grains. Purple grain wheat had the highest total and organic Se concentrations. Purple wheat also exhibited significantly higher Se transfer coefficient in roots, stem and leaves, and glumes, when compared to common wheat. Moreover, purple wheat had the highest Se uptake efficiency (e.g., JZ-496 with 31%) when compared to common wheat and black wheat. Regardless of the color, wheat grains met the Se-enriched criteria (150 μg Se kg−1) when grown in a natural Se-enriched area. Due to higher Se uptake and accumulation, purple wheat grain genotypes, such as JZ-496, are recommended for wheat breeding programs aiming for high Se functional foods.
Straw return-enhanced soil carbon and nitrogen fractions and nitrogen use efficiency in a maize–rice rotation system
- Yanwen Wang, Mingguang Qin, Ming Zhan, Tianqi Liu, Jinzhan Yuan
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- 31 January 2024, e5
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Considering straw resource utilization and air pollution prevention, straw return has been commonly practiced in China. However, the practicability of plenty straw return in an emerging maize–rice rotation and their effects on soil C and N pools have not been extensively investigated. This study has been conducted to examine the effects of straw return on soil nutrients, soil functional C and N fractions, and then to figure out their relationships with yield and N use efficiency. Two treatments of straw return (S2Nck) and without straw return (S0Nck) were compared in 3-year field experiment, and subplots without N application were added in their respective plots in the third year. The results showed that, relative to the control (S0Nck), straw return significantly increased soil mineralized nitrogen (Nmin), available P, and exchange K content by 11.7%, 41.1%, and 17.4% averaged across 3-year experiments, respectively. Straw return substantially increased soil dissolved organic C, microbial biomass C, and microbial biomass N content by 73.0%, 25.2%, and 36.8%, respectively. Furthermore, straw return markedly increased C and N retention in particulate organic matter in microaggregates (iPOM) and mineral associated organic matter within microaggregates (intra-SC), but significantly reduced in free mineral associated organic matter (free-SC) fraction. The structural equation modeling analysis showed that yield and the partial factor productivity of N were positively correlated with labile and slow soil C and N fractions. Consequently, straw incorporation significantly increased grain yields of maize by 14.7% and rice by 15.1%. The annual potential reduction proportion in fertilizer-N induced by straw return was estimated to be 25.7% in the third year. This study suggests that the incorporation of straws is an effective way to enhance soil nutrients and regulate soil C and N pools to improve crop production and has the potential to reduce N fertilizer application under maize–rice rotation in subtropical regions.
Resistance of sugarcane hybrids to internode borer Chilo sacchariphagus indicus (Lepidoptera: Crambidae)
- P. Mahesh, B. Singaravelu, J. Srikanth, K. P. Salin, K. Chandran, R. Nirmala
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- 21 February 2024, e6
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A four-year field study (2013–2016) was conducted to screen Indian sugarcane hybrids together with two susceptible checks against internode borer Chilo sacchariphagus indicus (Kapur) (Lepidoptera: Crambidae) in endemic locations of Tamil Nadu State, India. Each year, borer incidence on cane basis and intensity on internode basis were assessed at harvest to eliminate susceptible entries. Of the total 535 hybrids screened, only Co 293 emerged as resistant at the end of fourth year trial which was confirmed in tests under controlled conditions with artificial infestation. A modified relative resistance ratio computed using incidence and intensity also confirmed its resistance to the borer. In laboratory oviposition choice tests with excised leaves of the resistant Co 293 and susceptible hybrids Co 86032 and Co 1060, percent of leaf bits oviposited, egg masses laid, and egg numbers deposited were significantly lowest in Co 293. Also, an oviposition preference index computed for both egg mass number and egg number was significantly lowest for Co 293 which suggested antixenosis. Larval survival was significantly lowest in Co 293 with 5 to 10-fold higher neonate mortality than in the two susceptible hybrids. Prolonged larval development period and lower fecundity were observed when the borer was reared on Co 293 which indicated antibiosis. A relative suitability ratio developed from larval and pupal durations also indicated lower suitability of Co 293. Among the plant morphological characters examined, leaf length and cane thickness positively influenced borer incidence; loose sheath-clasp was associated with higher borer incidence. Among 12 shoot phenolics quantified, eight were present in higher quantities in Co 293 suggesting their role in antibiosis. Co 293 identified as resistant hybrid in the present study has the potential to be used as a parent in breeding programs for C. sacchariphagus indicus resistance.
Drought responses in Coffea arabica as affected by genotype and phenophase. I – leaf distribution and branching
- Miroslava Rakocevic, Fabio Takeshi Matsunaga, Ricardo Antônio Almeida Pazianotto, José Cochicho Ramalho, Evelyne Costes, Rafael Vasconcelos Ribeiro
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- 01 March 2024, e7
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In Coffea arabica, there is a small genetic distance between wild and bred genotypes. However, coffee genotypes express differential acclimation to multiple drought cycles, allowing them to successfully deal with water-limiting conditions. We hypothesized that bred coffee cultivars have a plant structure less sensitive to drought than wild genotypes. Plant and leaf architecture were analyzed over the coffee strata of two cultivars (Iapar 59 and Catuaí 99) and two wild Ethiopia accessions (‘E083’ and ‘E027’) grown under rainfed conditions and irrigation. During two consecutive productive years, evaluations were taken at leaf and berry expansion (BE1 and BE2) and harvest (BH1 and BH2) phenophases. The plant canopy was divided into up to four strata of 40 cm of thickness. Topological and geometric coding of coffee trees was performed in three botanical scales – metamers, branches, and plants in multiscale tree graphs (MTGs), following the VPlants modeling platform. Leaf and branch area per plant increased with tree structure development, being always significantly higher in irrigated than in rainfed plants over all phenophases. The individual leaf area was the least sensitive to water regime in Catuaí 99, while the 2nd order axis elevation – angle in relation to horizontal plane, ranging from 0° to 90° – of bred cultivars was less sensitive to drought than in ‘E083’. This finding partially corroborated our hypothesis that orchestrated reprograming of leaf/branch responses over the vertical plant profile were less sensitive to water availability in cultivars than in wild accessions. Leaves of 2nd to 4th-order branching were roughly plagiophile, while the 1st-order leaves were classified as extremophiles. When the coffee leaves were planophile, irrespective of genotype, this pattern was found at the lowest, 1st plant stratum, and the newest developed 4th stratum. Such responses were not obligatorily related to water regime, similar to branch elevation – with exception of ‘E083’, very sensitive to drought. Taken together, our data suggest that the leaf and branch elevations in C. arabica were more influenced by light distribution through the canopy profile – i.e., self-shading – than by water availability.
Plant growth regulators improve root growth of rice seedlings after mechanical transplanting and increase grain yield
- Jichao Tang, Zhimin Zhang, Shahbaz Atta Tung, Bilin Lu, Wenjia Yang
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- 08 March 2024, e8
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Enhancing seedling quality and promoting root growth post-transplantation are crucial for improving mechanically transplanted rice productivity. Here we investigated the impact of various plant growth regulators on hybrid and conventional rice varieties. Treatments, including two-diethylaminoethyl hexanoate (DA-6, 10 mg L−1), a combination of potassium 3-indole-butyrate + potassium 1-naphthylacetate + 6-benzylaminopurine (C3, 50 + 50 + 10 mg L−1), potassium 3-indole-butyrate + potassium 1-naphthylacetate + 1-triacontanol (C4, 50 + 50 + 50 mg L−1), potassium 3-indole-butyrate + potassium 1-naphthylacetate + 1.8% sodium nitrophenolate (C5, 50 + 50 + 1 mg L−1), and a combination of potassium 3-indole-butyrate + potassium 1-naphthylacetate + 1.8% sodium nitrophenolate + DA-6 (C6, 50 + 50 + 1 + 10 mg L−1), were sprayed either 3 or 10 days before transplanting. Seedlings sprayed 10 days before transplanting exhibited a higher number of white roots and total roots at the returning green stage, along with increased grain yield, irrespective of the plant growth regulator used. The C6 combination emerged as the most effective treatment, enhancing the growth of both hybrid and conventional rice seedlings, accelerating the growth rate of white roots and total roots, and increasing the length of the longest white root during the greening period, ultimately resulting in higher grain yield. Our findings demonstrate that pre-transplantation application of a combination of plant growth regulators positively influences rice seedling growth.
Does coinoculation with bradyrhizobia and cyanobacteria improve groundnut growth and yield?
- Diva Souza Andrade, Gisele Milani Lovato, Glaciela Kaschuk, Mariangela Hungria
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- 11 March 2024, e9
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Groundnut plants can obtain N from N2 fixation via symbiosis with rhizobia, and inoculation with selected strains can improve grain yields. We report the results of four field experiments carried out under subtropical conditions to confirm whether microbial inoculants can improve groundnut performance through the effects of single inoculation with Bradyrhizobium arachidis (SEMIA6144), coinoculation with Arthrospira platensis (IPR7059) or Synechocystis sp. (IPR7061), or N fertilization with 100 kg ha-1 N on plant growth, nodulation, N accumulation in tissues, grain protein concentration (GPC), and grain yield. There were no effects of inoculation treatment or N fertilizer on shoot or root dry weight. In clayey soil, coinoculation with B. arachidis and cyanobacteria increased grain productivity by an average of 19% compared to that in the noninoculated control. In this clayey soil with a higher P content, regardless of whether coinoculated with B. arachidis or cyanobacteria or single inoculated, grain productivity was 16% greater on average than that resulting from N fertilizer addition. In conclusion, the success of rhizobial inoculation in groundnuts is dependent on the soil, probably due to P limitation and weather conditions.
Potential contribution of agronomic practices and conservation agriculture towards narrowing smallholders’ yield gaps in Southern Africa: lessons from the field
- Isaiah Nyagumbo, Donald Nyamayevu, Lovemore Chipindu, Donald Siyeni, Domingos Dias, João Vasco Silva
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- 19 March 2024, e10
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Smallholders in Southern Africa continue to grapple with low maize productivity despite this being the staple food crop. This study sought to analyze and isolate the relative contribution of agronomic practices to maize yields obtained by smallholders in Malawi and Mozambique using data generated from on-farm trials testing the performance of conservation agriculture cropping systems. The trials were implemented in two communities, namely Kasungu district in Malawi and Sussundenga district in Mozambique, and ran for seven consecutive growing seasons starting in 2010–2011. Maize yield was measured annually in the on-farm trials, which included a ‘control treatment’ representing an improved farm practice, and in neighboring fields managed by the same farmers on their own, hence representing a ‘true farm practice’. Results indicated that maize yield increased linearly with increasing plant population at harvest at both sites. On average, an increase in plant population at harvest by 1000 plants ha–1 resulted in an increase in maize yield of 90 and 63 kg ha–1 at Kasungu and Sussundenga, respectively. The greatest maize yields were obtained when plant population at harvest exceeded 40 000 plants ha–1. Yet, the plant population at harvest was below the generally recommended optimum for most of the cropping systems studied and in most growing seasons. Furthermore, the use of agronomic practices alone without conservation agriculture (i.e., improved varieties, fertilizer management, and timely weed control) resulted in maize yield gains of as much as 54% and 43% relative to the ‘true farm practice’ at Kasungu and Sussundenga, respectively. Overall, the proportion of these yield increases relative to the ‘true farm practice’ accounted for by agronomic practices amounted to 53–70% and 57–85% at Kasungu and Sussundenga for the highest to the lowest-yielding cropping system. Although conservation agriculture significantly improved maize yield at both sites, such increases were smaller in magnitude compared to the yield gains derived from improved agronomic practices. The study suggests that considerable strides toward narrowing maize yield gaps in Southern Africa can be achieved through improvement of current crop management practices, let alone adhering to the conservation agriculture principles of minimum tillage, residue retention, and crop diversification.
Corrigendum
Plant growth regulators improve root growth of rice seedlings after mechanical transplanting and increase grain yield – CORRIGENDUM
- Jichao Tang, Zhimin Zhang, Shahbaz Atta Tung, Bilin Lu, Wenjia Yang
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- 12 April 2024, e11
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Research Article
Agronomic performance of disc chain harrow as a conservation agriculture tool for a one-step cover crop termination and seedbed preparation
- Mattia Trevini, Giacomo Tosti, Paolo Benincasa
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- 25 April 2024, e12
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Cover crops and conservation soil tillage are reconsidered in cropping systems for their several agronomical and ecosystem services. In this frame, an important role is played by cover crop termination and seedbed preparation, which are crucial for a timely and successful establishment of the following cash crop. This work was aimed at testing a disc chain harrow for terminating a cover crop of hairy vetch and preparing a seedbed for soybean and defining its operational characteristics. A total of three trials were carried out to (1) compare two types of discs in two different front + rear combinations and two different working speeds (8 vs. 14 km h−1) in terms of efficacy of hairy vetch termination; (2) evaluate the seedbed preparation by the disc chain in terms of soybean establishment as a following cash crop; (3) evaluate operational characteristics (working speed, fuel consumption, absorbed power, etc.) of the disc chain at the two different speeds. Results demonstrate that the disc chain is a valid tool for cover crop termination and seedbed preparation in a conservation tillage approach. The quality of work was affected by the type of disc and the working speed. The disc chain showed good operating performance, with low mechanical pulling force, low energy requirement for traction, and low fuel consumption as compared to alternative conservation practices for cover crop termination and/or shallow soil tillage.
Physiological and biochemical processes underlying the differential sucrose yield and biomass production in sugarcane varieties
- Tamires Da Silva Martins, José R. Magalhães Filho, Larissa Prado Cruz, Daniela F. S. P. Machado, Norma M. Erismann, Rose M. A. Gondim-Tomaz, Paulo E. R. Marchiori, André L. B. O. Silva, Eduardo Caruso Machado, Rafael Vasconcelos Ribeiro
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- 14 May 2024, e13
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Sucrose yield in sugarcane is a complex process regulated by both environmental and endogenous factors. However, the metabolic balance driving vegetative growth and sucrose accumulation remains poorly understood. Herein, we carried out a comprehensive assessment of carbohydrate dynamics throughout the crop cycle in two sugarcane varieties varying in biomass production, evaluating the carbon metabolism in both leaves and stalks. Our data revealed that the decline in photosynthetic rates during sugarcane maturation is associated not only to accumulation of sugars in leaves but also due to stomatal and non-stomatal limitations. We found that metabolic processes in leaves and stalks were intrinsically linked. While IACSP94-2094 had higher stalk sucrose concentration than IACSP95-5000, this latter produced more biomass. Compared to IACSP95-5000, IACSP94-2094 showed higher sucrose phosphate synthase (SPS) activity in leaves and stalks, along with lower soluble acid invertase (SAI) activity in leaves during the maximum growth stage. Interestingly, IACSP94-2094 also exhibited higher stalk SPS activity and lower stalk SAI activity than IACSP95-5000 during maturation. High biomass production by IACSP95-5000 was associated with higher sucrose synthase (SuSy) and SAI activity in leaves and higher SuSy and soluble neutral invertase (SNI) activity in stalks when compared to IACSP94-2094 during the maximum growth. Despite the contrasting strategies, both varieties displayed similar total sucrose yield, a balance between sucrose concentration and biomass production. This phenomenon implies the presence of a compensatory mechanism in sugarcane, with high biomass production compensating low sucrose accumulation and vice versa.
Factors influencing the variation in canopy light extinction coefficient (k) among pisifera parents of two oil palm origins
- Cornelis J. Breure
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- 17 May 2024, e14
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The canopy light extinction coefficient (k) is defined as the exponential decline in the amount of light passing through the leaf layers as a function of leaf area index (LAI). This definition is standard in oil palm breeding trials and models of canopy photosynthesis, where k is sometimes assumed to have a fixed value. The present experiment aims to validate the alleged constancy of k. Therefore, k was inferred from the fractional transmission of photosynthetically active radiation (PAR) and LAI, as obtained from dura x pisifera test crosses of Nigeria and Ghana pisifera origins. The palms were planted at two densities (135 and 160 palms ha−1) in North Sumatra in 2010. At the age of 7.5 years after planting, the area of newly opened leaves approached a maximum. Transmission of PAR remained very low and was only weakly related to k. By contrast, LAI exerted a strong negative effect on k, which generated, under both densities, considerable differences in k between both origins and among pisifera within an origin. The assumption of applying a fixed k value for a certain genotype or palm density, as obtained during leaf expansion at closed canopy, may therefore not be realistic. The present study suggests that the relationship of k with LAI over time merits further investigation, starting just before canopy closure.
Impact of soil type and harvest season on the ratooning ability of sugarcane varieties
- Njabulo Eugene Dlamini, Angelinus C. Franke, Marvellous Zhou
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- 24 May 2024, e15
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Sugarcane varieties differ in their ratooning ability (RA), and it is hypothesized that soil types and harvest seasons impact varieties’ RA. However, the effects of these factors on varieties’ RA remain unclear. This study aimed to assess the RA of different commercial sugarcane varieties (NCo376, N19, N23, N25, and N36), and establish the effects of soils and seasons on ratoon yields of these varieties in Eswatini. Fifteen years data on tons cane per ha per annum (TCHA) and tons sucrose per ha per annum (TSHA) achieved by plant cane and seven ratoon crops were collected from four commercial growers and analysed using linear regression models. The varieties significantly differed in RA. Variety N25, which had the highest plant cane yields (121.3 TCHA and 16.7 TSHA), had the sharpest yield decline over ratoon crops (–2.74 TCHA and −0.33 TSHA), suggesting that this variety is more suitable for short crop cycles. Variety N36 had second highest plant cane yields (111.7 TCHA and 16.4 TSHA) and a lower ratoon yield decline (–1.38 TCHA and −0.16 TSHA) than N25, suggesting that it is suitable for longer ratoon crop cycles. While soil type and harvest season significantly affected the relative yields of varieties, they did not significantly impact their RA, indicating that differences in varieties’ RA were driven by genotype and were relatively stable across environments. This suggests that tests to assess the adaptability of varieties should be conducted in multiple environments, while testing the RA of varieties may be conducted in fewer environments.
Effects of shade tree legumes on cacao biomass and bean yields after 20 years of intercropping in Ivory Coast
- Brahima K. Silue, Armand W. Koné, Alain J.A. Kotaix, Klotioloma Coulibaly, Sékou Aïdara, Lydie Chapuis-Lardy, Dominique Masse
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- 24 May 2024, e16
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The choice of tree species planted with cacao trees is essential for ensuring the efficiency and sustainability of cacao farming systems. This raises the question of the long-term impact of associated tree legumes (ATLs) on cacao bean yields and biomass accumulation. This study was carried out in accordance with four-block randomised experimental design in Divo (Ivory Coast, West Africa). The study involved cacao-Albizia lebbeck (Cacao-Alb) and cacao-Acacia mangium (Cacao-Aca) intercrops and unshaded cacao plots (Control). After 20 years of intercropping, we assessed cacao dendrometry (height, circumference, biomass, and biomass C-stock) and production (number of pods per tree and bean yield at the plot level) as well as soil fertility (soil organic matter (SOM) concentration) at various distances from ATLs (D1:0–1.75 m; D2:3.25–5 m; D3:7–9 m). The distance from the ATLs had no significant effect on the measured cacao dendrometric parameters, except for cacao height. In contrast, the Cacao-Aca association had a negative impact on the SOM concentration (−22%), cacao tree height (−6.15%), and productivity parameters (biomass: −12.4%; bean yield: −43%). However, Cacao-Alb and the Control had no significant differences in terms of SOM, tree biomass, or bean production. Intercropping cacao with the tested tree legumes did not enhance cacao productivity and, in some cases, hindered it, depending on the ATL species. This study highlighted the importance of identifying appropriate shade tree legume species that could be promoted in cacao-based agroforestry systems.
Low soil phosphorus availability has limited effects on wood traits in young plants of five eucalypt species
- Franklin Magnum de Oliveira Silva, Helena Augusto Gioppato, Alexandre Augusto Borghi, Sara Adrián López Andrade, Paulo Mazzafera
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- 27 May 2024, e17
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Plant-derived products rely heavily on the availability of phosphorus (P) in the soil. With reserves of P-rocks being limited, there is a growing demand to enhance the efficiency of P utilization by crops. Eucalypts, an important economic crop in many countries, is a source of timber, coal, essence oils, and cellulose. After identifying low P tolerant and susceptible species in a previous study, we explored the various physiological and biochemical responses of these same species to low P availability. The aim was to expand our understanding of how different P-nutrition responses might impact eucalypt wood production and traits related to its quality. Our results indicate that low soil P minimally affects physiological wood parameters in the young trees of Eucalyptus acmenoides, Corymbia maculata, E. grandis, E. globulus, and E. tereticornis. Decreases in cellulose contents and increases in lignin content and syringyl and guaiacyl (S/G) ratios were observed under low P and only in E. acmenoides plants. Wood density remained unaffected in all species. Additionally, bark, stem, and root P concentrations increased under sufficient P conditions in E. globulus, E. grandis, and E. tereticornis. These findings suggest that these plant parts may act as reserve pools of this nutrient.
Exchangeable molybdenum concentration in lowland paddy fields of Sri Lanka as affected by the differences in agro-climatic zones, soil orders, and water sources
- Indeera Hettiarachchi, Mojith Ariyaratne, Upul Rathnayake, Ranga Madushan, Harsha Kadupitiya, Rohana Chandrajith, Lalith Suriyagoda
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- Published online by Cambridge University Press:
- 12 September 2024, e21
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Molybdenum (Mo) is an essential micronutrient for plants. However, Mo status in Sri Lankan paddy fields as affected by climate and soil is not known. This study was conducted to (i) determine the distribution of exchangeable Mo concentration, and (ii) examine the interactive effects of the agro-climatic zone (ACZ), soil order, water source, and their interactions in determining exchangeable Mo concentration in lowland paddy fields of Sri Lanka. A total of 3,719 soil samples representing six ACZs, six soil orders, and three water sources were collected using a stratified random sampling approach. Exchangeable Mo concentration was determined after extracting in 0.01 M CaCl2 solution and detected using inductively coupled plasma-mass spectrometry. Soil Mo concentration varied in the range of 0.01 to 245 µg kg−1 with a mean of 25.9 µg kg−1. Samples collected from the Wet zone, particularly Wet zone Low country, had higher Mo concentrations than those reported in other ACZs. Among the soil orders tested, Histosols had a higher Mo concentration while that in other soil orders was similar. Rainfed paddy fields had more Mo than supplementary irrigated paddy fields. Spatial maps were generated to visualise the geographical variation in soil Mo concentration. Due to the presence of a spatial heterogeneity of exchangeable Mo concentration, it is important to implement ACZ, soil, and water source-based strategies to improve Mo status in Sri Lankan paddy fields.
Optimizing soil and plant functions: combinatory design of fertilizing resources assemblage for rainfed rice in Madagascar
- Manoa Raminoarison, Benoît Jaillard, Tantely Razafimbelo, Koloina Rahajaharilaza, Eric Blanchart, Jean Trap
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- 12 September 2024, e18
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The lack of affordable mineral fertilizers and scarcity of organic materials cause decline in soil fertility for smallholder farmers and producers in the highlands of Madagascar, challenging crop productivity. To fulfill plant growth and nutrition, we explored the effect of 132 combinations of 17 different fertilizing resources, both organic and mineral, on rice growth and nutrition using a greenhouse experiment. Two clustering approaches were used to evaluate the effects of fertilizing resources: elemental clustering and functional clustering. Elemental clustering grouped resources based on their elemental intrinsic composition, while functional clustering grouped resources based on their effect in improving plant growth and nutrition when combined in soil. We found that some resources closely grouped based on their elemental composition exhibited different effects on plant growth and nutrition when combined in soil. Zebu horn emerged as a particular organic resource in elemental clustering, and a key resource in functional clustering by promoting plant growth and nutrition when combined with other resources in soil. Its unique elemental composition played a significant role in driving positive interactions with other resources. We proposed to extend the concept of ‘assembly motif’ within soil fertilization strategy, suggesting that the combination of functional groups of resources determines better their fertilizing effect than their elemental composition. Resources inducing high interaction effects should be combined with those having high elemental composition to optimize crop productivity.
Characterisation of bitter vetch (Vicia ervilia (L.) Willd) ecotypes: An ancient and promising legume
- Soumaya Boukrouh, Ali Noutfia, Nassim Moula, Claire Avril, Julien Louvieaux, Jean-Luc Hornick, Mouad Chentouf, Jean-François Cabaraux
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- Published online by Cambridge University Press:
- 12 September 2024, e19
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Bitter vetch (Vicia ervilia (L.) Willd) is a promising legume, drought tolerant, mainly used in the Mediterranean area for its grains as a source of proteins in animal feed. However, it is an underused crop cultivated in marginal soils. Ecological, agro-morphological, and bromatological diversity evaluations were conducted to study its reintroduction potential. Seeds of seventeen ecotypes were collected in seventeen farms located in Northern Morocco in 2018. The cultivation was realised during the 2019 and 2020 growing seasons using a randomised complete block design with three replicates. Agro-morphological data were collected at the start of flowering, full flowering, and pod setting phenological stages. Yield component assessment and grain and straw bromatological characterisation were performed at maturity. The results indicated significant variations between ecotypes for almost all parameters and interesting results about yield (1 t ha–1) but lower protein content (22.9% of dry matter) compared to other ecotypes of the Mediterranean region. The estimated genetic parameters could emphasise the possibility of selecting highly productive and nutritive cultivars. However, interannual variations were also detected, making the selection of the ecotypes harder. No significant correlations were observed between agro-morphological and bromatological traits of grains and geographical distances. Multivariate analyses (principal component analysis and heatmap) clustered ecotypes into five groups, where the ecotypes included in the second cluster were the most interesting candidates for developing high-yielding and nutritive varieties. That is why this plant could be considered of interest, especially in these times of climate change.