Search Results (17)

Nitrogen (N) fertilizer application is one of the most crucial agronomic management practices for increasing grain yield in maize crops. However, the long application may adversely affect soil quality. For achieving sustainable agricultural production, the current research set out to evaluate the short-term effects of the addition of zeolite as a soil amendment and N fertilization on the maize growth, yield, quality, N- and water-use efficiency in three locations (Athens, Messolonghi, and Karditsa) in Greece. Each experiment set up during the spring–summer 2024 cultivation period was laid out in a split-plot design with three main plots (Zeolite treatments: 0, 5, and 7.5 t ha⁻¹) and four sub-plots (N fertilization treatments: 0, 100, 150, and 200 kg N ha⁻¹). The results revealed that increasing the zeolite application rate from 0 to 7.5 t ha⁻¹ led to a significant increase in grain yield, with the highest value (13.46, 12.46, and 14.83 t ha⁻¹ in Athens, Messolonghi, and Karditsa, respectively) observed at 7.5 t ha⁻¹. In the same manner, the increasing inorganic N fertilization rate from 0 to 200 kg N ha⁻¹, also increased the grain yield. In general, most of the soil properties (soil organic matter, soil total nitrogen, total porosity, soil moisture content, and infiltration rate), root and shoot growth (root length density, plant height, leaf area index and dry weight), N content and uptake of the grains, and aerial biomass, as well as, thousand kernel weight, N harvest index (NHI), and water use efficiency (WUE), were positively affected by both of the examined factors. In conclusion, this study proved that the increasing rates of zeolite as a soil amendment and N fertilization up to a rate of 7.5 t ha⁻¹ and 200 kg N ha⁻¹, respectively, improved soil properties, promoted plant development, and increased grain yield, grain and biomass N uptake, NHI, and WUE of the maize crop cultivated in clay–loam soils and under Mediterranean conditions, where the experimental trials set up. Full article

Cultivating red oak lettuce in plant factories often encounters challenges in achieving the desired red leaf coloration. To make the leaves a pleasant red color, anthocyanins are key substances that need to be induced. This study aimed to evaluate the effects of increasing light intensity and irrigation methods on the growth and leaf color of red oak lettuce in a controlled environment. Two light intensities (300 and 400 µmol m⁻² s⁻¹) with white LEDs and two irrigation methods (circulating vs. non-circulating irrigation) were applied seven days before harvesting. The results indicated that plants grown with circulating irrigation exhibited significantly higher fresh and dry weights than those grown under non-circulating conditions, regardless of light intensity. When non-circulating irrigation was applied, shoot fresh weight decreased by approximately 22% on the harvesting day compared to the circulating treatments. Under the 400 µmol m⁻² s⁻¹ light intensity with non-circulating irrigation (400N-C), plants displayed the lowest lightness (L*) at 40.7, increased redness (a*) to −7.4, and reduced yellowness (b*) to 11.0. These changes in coloration were optimized by day 5 after treatment. Additionally, spectral indices, including normalized difference vegetation index and photochemical reflectance index, varied significantly among treatments. The 400N-C treatment also resulted in the highest anthocyanin content and antioxidant activity in red oak lettuce. These findings suggest that combining high light intensity with non-circulating irrigation before harvest can improve both the coloration and quality of red oak lettuce in plant factories with artificial lighting. Full article

The use of polymer-coated urea (PCU) can improve nitrogen use efficiency (NUE), compared to the application of rapid-release urea (RU). However, the effect of PCU-based nitrogen management on grain yield and the NUE of rice and its underlying mechanism remain unclear. A japonica rice cultivar Jinxiangyu 1 was grown in the field with four treatments including N omission (0N), split application of RU (Control), one-time application of 100% PCU (T1), and one-time application of 70% PCU + 30% RU (T2). Results showed that, compared to the control, the grain yield was significantly increased in the T2 treatment, while it was comparable in the T1 treatment. This was mainly due to increased total spikelets in the T2 treatment. Root oxidation activity (ROA) and root zeatin (Z) + zeatin riboside (ZR) content during booting were the distinct advantages of the T2 treatment, compared to either the control or T1 treatment, exhibiting significant or highly significant correlations with leaf photosynthesis. This process contributed significantly to total spikelets and total N uptake. Additionally, the T2 treatment absorbed more N than the control without reducing the internal N use efficiency (IE_N), primarily due to its unchanged harvest index (HI) driven by comparable non-structural carbohydrate remobilization. In conclusion, combining PCU with RU can enhance the coordination of root and shoot traits during booting while maintaining a competitive HI at maturity, thereby significantly improving grain yield and achieving a balance in N uptake and utilization. Full article

Clarifying the optimal combination of N fertilizer application rate and application method can maximize the yield of drip-irrigated sugar beet in arid areas, which is of great significance for reducing farmland N pollution and achieving sustainable agricultural development. In this three-year field experiment in Xinjiang, China, the effects of three N application rates [75 kg ha⁻¹ (N1), 150 kg ha⁻¹ (N2), and 225 kg ha⁻¹ (N3)] and three N application methods [the proportion of N applied at canopy rapid growth stage, taproot expansion stage, and sugar accumulation stage were (M₁) 100%: 0%: 0%, (M₂) 70%: 30%: 0%, and (M₃) 50%: 30%: 20%] on the dry matter accumulation (DMA) and distribution, leaf senescence, yield, and agronomic N use efficiency (aNUE) of drip-irrigated sugar beet were explored. The results showed that N application (N1, N2, and N3 treatments) increased the shoot DMA by 27.7% (three-year average), 52.6%, and 83.1%, and the taproot DMA by 28.3%, 43.2%, and 61.6%, respectively (p < 0.05), compared with CK (no N supply) treatment. The N application methods M₂ and M₃ increased the shoot DMA by 5.6% (three-year average) and 1.0% (p > 0.05), respectively, and the taproot DMA by 7.2% and 3.6% (p < 0.05), respectively, compared with M₁. In addition, M₂ could delay the end of shoot and taproot growth (t_e) and the occurrence of maximum growth rate (t_m). In particular, the N3M₂ treatment increased the leaf area index (LAI) by 20.4–75.9% (p < 0.05) compared with other treatments by increasing the leaf area duration (LAD) and decreasing the leaf senescence rate (LSR). The taproot yield and sugar yield of N3M₂ treatment reached the maximum at harvest time, but there was no significant difference in taproot yield and sugar yield between N3M₂ treatment and N2M₂ treatment. The aNUE in N2M₂ treatment was the highest (p < 0.05), which was 1.29–7.85 times higher than that of other treatments. Therefore, reducing the N application rate from 225 kg·ha⁻¹ to 150 kg·ha⁻¹ and applying 70% and 30% of 150 kg N ha⁻¹ at the canopy rapid growth stage and the taproot expansion stage, respectively, could achieve the goal of increasing sugar beet yield and N use efficiency. This study will provide an important reference for the sustainable production of sugar beet under drip irrigation in Xinjiang, China. Full article

Nitrogen is the most commonly managed mineral nutrient in olive groves because it is essential for plant growth. The precise management of N fertilization in olive cultivation is still not fully clarified, but it is essential for providing sustainable production. A nitrogen fertilizer experiment with olive trees (cv. Kalinioti) was carried out over a six-year period. Seven levels of nitrogen fertilizer given as ammonium nitrate (control, 1, 2, 3, 4, 5, and 6 kg/tree) were annually applied in order to determine the effect of nitrogen on vegetative growth, fruit set, fruit weight, yield, maturation index, and leaf N, P, and K concentrations. The results indicate that, under these conditions, application of up to 4 kg NH₄NO₃/tree significantly increased yield to 62.5 kg/tree compared to the control (37.09 kg/tree). The positive effect was attributed to the initial and final fruit set increases (7.63 and 3.73%, respectively at 4 kg NH₄NO₃/tree). However, the weight of 100 olives (W₁₀₀ = 331 g) at 4 kg NH₄NO₃/tree obtained during harvest was considerably lower compared to the control (W₁₀₀ = 384 g). Higher nitrogen rates decreased yield while increasing overall shoot growth. Nitrogen fertilization did not significantly influence the oil content of olive fruit. Fruit weight, maturation index, and concentration of oil reached maximum levels in the beginning of December, indicating a suitable start to olive harvesting. The concentration of N in olive leaves increased from 1.23% to 2.38% as fertilizer levels increased from 0 to 6 kg NH₄NO₃. Maximum yield was achieved at a level of 6 kg NH₄NO₃/tree, which corresponded to 2.01% N in leaves. The results suggest that application of 3 kg NH₄NO₃/tree can be recommended for table olive production, due to the fact that fruit weight was not decreased, while fertilization with 4 kg NH₄NO₃/tree was suitable for oil olives. Full article

According to numerous chamber and free-air CO₂ enrichment (FACE) studies with artificially raised CO₂ concentration and/or temperature, it appears that increasing atmospheric CO₂ concentrations ([CO₂]) stimulates crop yield. However, there is still controversy about the extent of the yield stimulation by elevating [CO₂] and concern regarding the potential adverse effects when temperature rises concomitantly. Here, we tested the effects of natural elevated [CO₂] (ca. 120 ppm above the ambient level in 100 years ago) and warming (ca. 1.7–3.2 °C above the ambient level 100 years ago) on rice growth and yield over three crop seasons via a past reference investigation and current experiment (PRICE) study. In 2020–2022, the rice cultivar Tamanishiki (Oryza sativa, ssp. japonica) was grown in Wagner’s pots (1/2000 a) at the experiment fields of Chonnam National University (35°10′ N, 126°53′ E), Gwangju, Korea, according to the pot trial methodology of the reference experiment conducted in 1920–1922. Elevated [CO₂] and temperature over the last 100 years significantly stimulated plant height (13.4% on average), tiller number (11.5%), and shoot biomass (10.8%). In addition, elevated [CO₂] and warming resulted in a marked acceleration of flowering phenology (6.8% or 5.1 days), potentially leading to adverse effects on tiller number and grain yield. While the harvest index exhibited a dramatic reduction (12.2%), grain yield remained unchanged with elevated [CO₂] and warming over the last century. The response of these crop parameters to elevated [CO₂] and warming was highly sensitive to sunshine duration during the period from transplanting to heading. Despite the pot-based observations, considering a piecewise response pattern of C₃ crop productivity to [CO₂] of <500 ppm, our observations demonstrate realistic responses of rice crops to elevated [CO₂] (+120 ppm) and moderate warming (+1.7–3.2 °C) in the absence of adaptation measures (e.g., cultivars and agronomic management practices). Hence, our results suggest that the PRICE platform may provide a promising way to better understand and forecast the net impact of climate change on major crops that have historical and experimental archived data, like rice, wheat, and soybean. Full article

Rice (Oryza sativa L.) is an important cereal crop worldwide due to its long domestication history. North-Eastern India (NEI) is one of the origins of indica rice and contains various native landraces that can withstand climatic changes. The present study compared NEI rice landraces to a check variety for phenological, morpho-physiological, and yield-associated traits under high temperatures (HTs) and elevated CO₂ (eCO₂) levels using molecular markers. The first experiment tested 75 rice landraces for HT tolerance. Seven better-performing landraces and the check variety (N22) were evaluated for the above traits in bioreactors for two years (2019 and 2020) under control (T1) and two stress treatments [mild stress or T2 (eCO₂ 550 ppm + 4 °C more than ambient temperature) and severe stress or T3 (eCO₂ 750 ppm + 6 °C more than ambient temperature)]. The findings showed that moderate stress (T2) improved plant height (PH), leaf number (LN), leaf area (LA), spikelets panicle⁻¹ (S/P), thousand-grain weight (TGW), harvest index (HI), and grain production. HT and eCO₂ in T3 significantly decreased all genotypes’ metrics, including grain yield (GY). Pollen traits are strongly and positively associated with spikelet fertility at maturity and GY under stress conditions. Shoot biomass positively affected yield-associated traits including S/P, TGW, HI, and GY. This study recorded an average reduction of 8.09% GY across two seasons in response to the conditions simulated in T3. Overall, two landraces—Kohima special and Lisem—were found to be more responsive compared to other the landraces as well as N22 under stress conditions, with a higher yield and biomass increment. SCoT-marker-assisted genotyping amplified 77 alleles, 55 of which were polymorphic, with polymorphism information content (PIC) values from 0.22 to 0.67. The study reveals genetic variation among the rice lines and supports Kohima Special and Lisem’s close relationship. These two better-performing rice landraces are useful pre-breeding resources for future rice-breeding programs to increase stress tolerance, especially to HT and high eCO₂ levels under changing climatic situations. Full article

Selecting cultivars with greater biomass results in higher yields and greater carbon sequestration. Storage of atmospheric carbon in the plant/soil pool contributes not only to food security but also to mitigating climate change and other agroecological benefits. The objective of this study was to determine: (1) grain, residue, and root biomass yields; (2) harvest indexes; (3) residue-to-product ratio; (4) root-to-shoot ratio; (5) biomass carbon and nitrogen contents; and (6) C:N ratios for two new and two old winter wheat cultivars. The greatest yield difference was found between old Srpanjka (the lowest) and new Kraljica (the highest) cultivar where grain, residue, root, and total biomass yield was higher by 38%, 91%, 71%, and 64%, respectively. Total biomass was composed of 40–47% grain, 10–11% roots, 32–36% stems + leaves, 9–11% chaff, and 1–2% spindle. The range of HI was 0.45–0.53, RPR 0.91–1.25, and R:S ratio 0.12–0.13. For all cultivars, positive carbon and negative nitrogen balance within the plant pool was determined. Still, root biomass and rhizodeposition carbon remain open questions for a better understanding of agroecosystems’ C dynamics. Full article

Salvia miltiorrhiza B., an herb used in traditional Chinese medicine, has been widely used to prevent and treat cardiovascular and other diseases. Currently, the majority of medicinal plants used in the US are imported from foreign countries, which involves transportation, quality control, and other issues. The objective of this study was to investigate the effect of nitrogen fertilization on growth and content of tanshinone I, tanshinone IIA, cryptotanshinone, and salvianolic acid B for Salvia miltiorrhiza B. in Mississippi. Plants were fertilized with one of five nitrogen (N) rates (0, 2, 4, 6, or 8 g N/plant from NH₄NO₃). Plants were harvested in November 2020 and 2021. Plants treated with 8 g N had higher plant growth index, leaf SPAD value, shoot and root number, shoot and root weight, maximum root length and diameter, shoot: root ratio, N concentration in root, and content of bioactive components compared to plants treated with 0, 2, 4 g N. Plants receiving 6 g N had similar shoot number, maximum root length, maximum root diameter, root weight and content of bioactive components compared to plants receiving 8 g N. However, plants receiving 6 g N had higher photosynthetic activity compared to plants receiving the higher N rate. Higher N rates increased plant growth and content of tested bioactive compounds. Full article

A decreased nitrogen (N) rate with increased planting density (DNID) is recommended as a feasible method to maintain rice grain yield and N-utilization efficiency. However, it is still unclear whether DNID could improve grain quality, particularly the edible quality of rice. Three high-yield rice with superior palatability (HYSP) and three high-yield rice with inferior palatability (HYIP) were grown under DNID and local cultivation practices (LCP) in the same paddy fields during the 2018 and 2019 rice planting seasons. HYSP exhibited similar grain yields to HYIP under both cultivation treatments. HYSP had more spikelets per m² through panicles per m², while having lower spikelets per panicle and 1000-kernel weight than HYIP. DNID increased panicles per m² and 1000-kernel weight and decreased spikelets per panicle of HYSP and HYIP compared with LCP. HYSP exhibited more biomass accumulation during heading to maturity under NDID and LCP (p < 0.05), which is supported by a higher leaf area index (LAI) and SPAD values after heading. DNID reduced shoot biomass weight and non-structural carbohydrate, while increasing harvest index and NSC remobilization reserve, especially for HYSP (p < 0.05). HYSP had a higher amylopectin content, total starch content, gel consistency, stickiness, and overall palatability (p < 0.05), while it had a lower hardness (p < 0.05) than HYIP. Compared with LCP, DNID increased the amylose content, amylopectin content, total starch content, gel consistency, stickiness, and overall palatability, while it decreased grain protein content and hardness of HYSP and HYIP. HYSP showed consistently higher peak viscosity, breakdown, and gelatinization temperatures (p < 0.05), while it showed lower setback (p < 0.05) than HYIP. For HYSP and HYIP, DNID increased the peak viscosity, breakdown, and gelatinization temperatures (p < 0.05), while it decreased the setback compared with LCP. Generally, the results indicated that coordinated yield components, more post-heading biomass accumulation, lower amylose content, higher peak viscosity and breakdown with lower setback, and higher gelatinization temperatures facilitated high-level grain yield and excellent cooked rice palatability of HYSP. DNID is a feasible method to maintain rice grain yield and enhance the quality of cooked rice for edible properties. Full article

Desertified land covers one-fourth of the world’s total land area. Meeting the high food demands in areas affected by desertification is a major problem. This case study provided fundamental information to demonstrate the potential for utilizing the desertified land. The soybean trial was established in two sandy clay loam soils (desertified land) and one silty clay loam soil. Two types of biochar were applied as treatments. We aimed to investigate the response of soybean plants to soil structure, soil nutrient condition, and biochar amendment in the two types of soil. In addition, ridge regression was employed to model the plant growth indicators by soil structure, soil nutrients condition, soil water content, and biochar amendment. We conclude that (1) overall soil productivity in sandy clay loam soil is lower than in silty clay loam soil. The sandy clay loam soil may have high efficacy for crop production due to its higher harvest index. (2) Aggregate size 0.5–1 mm, 1–2 mm, and 2–3 mm indicated more important in plant biomass formation in silty clay loam soil. The low aggregate stability of sandy clay loam soil made the field more vulnerable to wind erosion in the semi-arid monsoon climate. (3) Cob biochar and wood biochar increased soybean shoot biomass by 48.7% and 45.0% in silty clay loam soil. (4) The higher N-fixing ability of nodules in sandy clay loam soil indicates an advantage to reduce the use of N-fertilizers in desertified areas. (5) Exponential polynomial regression ameliorated the accuracy of prediction of plant growth indicators in comparison to linear regression. Full article

The quality of green tea is greatly influenced by the harvest standards for young shoots. The present field experiment was conducted to characterize the young shoot populations, yields, and nitrogen (N) demands of tea plants subjected to four different harvest standards, i.e., buds with one, two, or three young expanding leaves (referred to as B1L, B2L, and B3L, respectively) and a combination of B1L and B3L (B1L/B3L) throughout the year. Weight per shoot was closely related to the number of expanding leaves and was greater in B3L than B1L and B2L, and also greater in summer and autumn than in spring, whereas B1L revealed the greatest young shoot density and highest N concentration. Annual shoot yield and shoot N content were largest in B3L and decreased in the following order: B3L > B2L ≈ B1L/B3L > B1L. However, in the early spring the shoot density, yield, and shoot N content of B1L were much higher than those of B3L. The harvest of B3L significantly reduced the biomass of brown roots and its ratio against the above-ground biomass compared to other harvest standards, suggesting a decreased allocation of carbon to the root system due to seasonal removal. The N dilution curve (N_ys = a × Y_ys^b, where N_ys is the shoot N content and Y_ys is the shoot yield) of spring tea differed markedly from those of summer and autumn teas, suggesting different coordination properties for shoot growth and N supply among the seasons. The annual harvest index (NHI) measured by ¹⁵N traces ranged between 0.18 and 0.23, indicating relatively low N allocation to young shoots, whereby large proportions (58.2–66.9% of the total ¹⁵N absorption) remained in the plant at the end of the experiment. In conclusion, the seasonal distribution of the shoot density, weight per shoot, yield, and N demands vary with harvest standards and highlight the importance of N precision management in tea production to be finely tuned to meet the changes in harvest season and requirements. Full article

The past three decades have seen a pronounced development of conventional japonica rice from the 1990s, although little information is available on changes regarding grain yield and nutrient use efficiency during this process. Nine conventional japonica rice released during the 1990s, 2000s, and 2010s were grown under a reduced nitrogen rate, with increased planting density (RNID) and local cultivation practice (LCP) in 2017 and 2018. The rice from the 2010s had 3.6–5.5% and 7.0–10.1% higher (p < 0.05) grain yield than the 2000s and the 1990s, respectively, under RNID and LCP. The harvest index contributed more to genetic yield gain from the 1990s to the 2000s; whereas from the 2000s to 2010s, yield increase contributed through shoot biomass. Genetic improvement increased total nitrogen (N), phosphorus (P), and potassium (K) accumulation, and their use efficiencies. The rice from the 2010s showed a similar grain yield, whereas the 1990s and 2000s’ rice exhibited a lower (p < 0.05) grain yield under RNID relative to LCP. RNID increased N, P, and K use efficiencies, particularly the N use efficiency for the grain yield (NUEg) of the 2010s’ rice, compared with LCP. For three varietal types, RNID increased the panicles per m², the filled-grain percentage, and the grain weight (p < 0.05) while decreasing spikelets per panicle of the 2010s’ rice. Compared with LCP, RNID reduced non-structural carbohydrate (NSC) content and shoot biomass, at heading and maturity, while increasing the remobilization of NSC and the harvest index, especially for the 2010s’ rice. Our results suggested the impressive progressive increase in grain yield and nutrient use efficiency of conventional japonica rice since the 1990s in east China. RNID could facilitate grain yield and NUEg for modern conventional japonica rice. Full article

Some silicate rocks are a rich source of potassium (K), with the possibility for use in agriculture. The present study aimed to evaluate the agronomic efficiency index (AEI) of nepheline syenite (NS) and phonolite (PN) rocks in comparison with potassium chloride (KCl) as a K source in maize production. An experiment was conducted in a greenhouse in Ilha Solteira, São Paulo, Brazil. A maize hybrid was grown in 8 L pots filled with 6 kg of soil with a low K concentration and contrasting physical attributes (medium and sandy texture). A completely randomized design in a 3 × 6 factorial scheme was used, consisting of three K sources (NS, PN, and KCl) and six rates (0, 50, 100, 150, 200, and 400 mg kg⁻¹) with four replications. All plants were harvested 45 days after emergence to evaluate biomass production, macronutrient (N, P, K, Ca, Mg, and S) concentration and uptake, stem diameter, and leaf chlorophyll index. After crop harvest, soil was collected for further chemical evaluation, which included organic matter (OM), pH, cation exchange capacity (CEC), H+Al, Al, sum of bases (SB), base saturation (BS), P, K, Ca, Mg, and S. In addition, AEI of NS and PN were also verified in relation to KCl. The application of NS and PN had a similar effect on soil chemical attributes (MO, pH, SB, CEC, and BS) as well as on the concentrations of K, Ca, Mg, and S, in both soils. The increase in NS and PN rates provided linear growth of shoot dry matter. Leaf macronutrient concentrations were similar for NS and PN compared to KCl. All three K sources (NS, PN, and KCl) increased K accumulation in maize plants. Maize treated with KCl had the largest AEI, followed by PN and NS. However, the results indicated similar AEI with both rocks as a K source for maize, especially with application of the highest K rates. This research demonstrated the efficiency of NS and PN as alternative K sources for maize. Full article

Eragrostis tef (Zucc.) Trotter (tef) is a small annual grain, panicle-bearing, C₄ cereal crop native to Ethiopia, where it is a major staple food. The objectives of the present study were to characterize the responses of two tef genotypes to escalating nitrogen (N) levels in terms of shoot, root, and grain biomass production, N concentration and uptake, and to determine an optimum N range at which tef performance is maximized. The N was applied in the irrigation water (Fertigation) in order to provide a consistent concentration of N in the root zone. A second goal was to test the feasibility of growing tef in the hot, arid conditions of the Northern Negev Desert. Two experiments were carried out in the Gilat Research Station (Negev region, Israel), each testing two different genotypes of tef (405B and 406W), and each including five replicates for each treatment. In the winter of 2015–2016, tef plants were grown in perlite filled pots in a walk-in plastic-covered tunnel. Five different N treatments were applied through fertigation, meaning the fertilizer was applied with the irrigation water (10, 20, 40, 80, 120 mg L⁻¹). All other nutrients were applied at the same sufficient rate. In the summer of 2016, tef plots were sown in open-field and applied with four different rates of N fertilization (0, 30, 60, 120 mg L⁻¹). Biomass of the different plant parts, SPAD values, N, P and K concentration, and the lodging index were recorded in each experiment. The harvest index was also calculated. Optimum N fertigation concentration in both experiments was between 40 and 80 mg L⁻¹, under which the time to flowering was decreased, and yield and grain protein concentration were optimized. Underfertilization caused a decrease in overall plant growth, whereas overfertilization caused an increase in vegetative growth at the expense of grain yield. Potassium uptake increased along with increased N availability, whereas P uptake did not. The fertilization rate will always need to take into account local soil and climate conditions. The field experiment also pointed to low harvest index as a major limitation on tef cultivation in the Northern Negev. Full article