This study aimed to explore the impact paths on soil organic carbon and crop yield of completely or partially substituting chemical N fertilizer with organic fertilizers. A four-year field experiment was conducted and included four treatments: (i) N0, no N fertilization application; (ii) NF, only synthetic N fertilizer application; (iii) 1/2OF, organic fertilizer substituted for 100% of the synthetic N fertilizer, with the total N application amount being equivalent to half that of NF; and (iv) 1/3OF + 2/3NF, organic fertilizer substituted for 1/3 of the synthetic N fertilizer with the total N application amount from organic and synthetic fertilizer being equivalent to that of NF. Soil total organic carbon (TOC), labile organic-carbon fractions (microbial biomass carbon (MBC), dissolved organic carbon (DOC), particulate organic carbon (POC), and easily oxidized organic carbon (EOC)), the carbon pool management index (CPMI), soil aggregated distribution, and water-stable aggregate-associated organic carbon were determined. Structural equation modeling (SEM) was used to clarify the impact paths of TOC and garlic yield changes under different N fertilizer treatments. Results showed that compared with N0 and NF, 1/2OF and 1/3OF + 2/3NF significantly increased TOC contents by 14.1–20.6%. Soil MBC, DOC, and EOC under 1/2OF were significantly higher than under N0, whereas the 1/3OF + 2/3NF treatment had significantly greater POC. The CPMI was improved by organic fertilizer treatment, with 1/2OF treatment being significantly higher than N0 and NF. The proportion of soil aggregate mass with particle sizes >2 mm was significantly greater under N0, while 1/3OF + 2/3NF significantly increased the proportion of particle sizes of 0.5–2 mm. Soil water-stable aggregate-associated organic carbon showed a trend of first increasing and then decreasing, with the largest particle sizes being 1–2 mm. Moreover, organic fertilizer significantly increased soil water-stable aggregate organic carbon compared with N0 and NF. Similarly, the garlic yield increased with organic fertilizer treatment, while 1/3OF + 2/3NF significantly increased the yield by 37.2% and 15.3%, respectively, compared with N0 and NF. Furthermore, SEM analysis indicated that fertilizer regimes could directly affect TOC and labile organic carbon components by affecting aggregate-associated organic carbon. In particular, aggregates with particle sizes of 0.5–2 mm played an important role, indirectly affecting garlic yield and CPMI. These results indicate that organic fertilizer application has the potential to improve soil organic-carbon content and garlic yield; moreover, fully applying organic fertilizer can reduce N fertilizer input while still maintaining an increase in soil organic carbon and crop yield in the short term. However, caution is still needed regarding of the type and quantity of organic fertilizer added in different cropping systems, and with different soil textures. Full article

Soybean is the main leguminous crop in Brazil, mostly grown in tropical soils with low potassium (K) availability. Therefore, the identification of new genotypes with efficient K uptake and utilization in environments with low exchangeable K content is an economically viable alternative to maximize crop yield in Brazil. A study was conducted to investigate the response of 25 modern high-yield soybean genotypes for K-use efficiency in a sandy tropical soil of the Brazilian Cerrado. Treatments were distributed in a completely randomized design in a 2 × 25 factorial scheme: two levels of K fertilization [20 mg K dm⁻³ (low level) or 200 mg K dm⁻³ (high level)] and 25 soybean genotypes with three replicates. Plant morphological traits, leaf K, and crop production components were measured. Based on grain production data, K-use efficiency (KUE) and response efficiency (RE) to K fertilization were calculated. Leaf area, shoot dry matter, pod number per plant, 1000-grain weight, and grain yield were the crop characteristics most limited by low soil K availability. The soybean genotypes “TMG7061 IPRO”, “BMX Bônus IPRO”, “RK6719 IPRO”, and “RK8317 IPRO” were classified as efficient in the use of soil K and are the most suitable genotypes to be cultivated in agricultural soils with low K availability. The genotypes “98R35 IPRO”, “HO Maracaí IPRO”, “BMX Bônus IPRO”, and “RK7518 IPRO” were classified as responsive to K fertilization and are the most recommended genotypes for cultivation in agricultural areas with the application of high K fertilizer rates. The genotype “BMX Bônus IPRO” simultaneously combines characteristics of K-use efficiency and response to K fertilization and hence can be grown in both K-deficient and optimal soils. Full article

Despite growing interest in controlled-release N fertilizers (CRNFs) because of their potential for enhancing nitrogen use efficiency (NUE) and economic returns, their comprehensive impact on machine-transplanted rice remains to be understudied. To address this gap, here, we present a two-year field experiment that assessed the impact of CRNF using mechanical deep placement fertilization (DPF) on rice cultivation. The study involved three CRNF types (bulk blending fertilizer (BBF), polymer-coated urea (PCU), and sulfur-coated urea (SCU)) and two fertilization methods (DPF and broadcast application), with a high-yield split fertilization of urea as a control (CK). The results showed that DPF, especially with SCU, greatly enhanced soil NH₄⁺-N concentrations, NUE, rice yield, and economic benefits compared to broadcast application. BBF consistently exhibited superior NUE and notable economic benefits, regardless of the application method used. Conversely, single-time application of PCU was less favorable for rice growth. In conclusion, for optimal economic benefits and NUE, DPF combined with single-time application of SCU is recommended. However, if deep application is not feasible and only broadcasting is possible in rice cultivation, BBF emerges as the ideal choice for both high NUE and significant economic returns. This research offers insights for improved nitrogen management in machine-transplanted rice, effectively optimizing yield, NUE, and profitability. Full article

This study aimed to investigate how transplanting date affects the agronomic and grain quality traits of two early-maturing rice varieties. The experiment was conducted in the rice research field of Chungnam Agricultural Research and Extension Services in South Korea and rice materials were transplanted at intervals of approximately 15 days from 16 April to 16 July in 2019 and 2020. Results showed that agronomic and grain quality traits varied according to the transplanting date and earlier transplanting resulted in a longer period of days from transplanting to heading (DTH). The spikelet number m⁻² was highly correlated with the milled rice yield (r = 0.963 ** for Jinbuol, r = 0.909 ** for Yeoreumi) and it significantly decreased as the transplanting date was delayed, which was leading to lower yield. The mean temperature during the grain filling stage had a negative correlation with head rice rate (r² = 0.825 ** for Jinbuol, r² = 0.803 ** for Yeoreumi) and the number of days from transplanting to heading showed negative correlation with protein content (r² = 0.777 ** for Jinbuol, r² = 0.833 ** for Yeoreumi). Therefore, increasing the number of days from transplanting to heading date can lead to higher milled rice yield and lower protein content and avoiding heading dates on 17 July can improve the appearance traits. As a result, it is suggested that early transplanting is advantageous to increase the milled rice yield and grain quality of early-maturing rice. Full article

This paper explores the effects of water and nitrogen management on drip irrigated rice root morphology, nitrogen metabolism and yield, clarifies the relationship between root characteristics and yield formation. Normal irrigation (W₁, 10,200 m³/hm²) and limited irrigation (W₂, 8670 m³/hm², 85% of W₁) were set with nitrogen-efficient variety (T-43) and nitrogen-inefficient variety (LX-3) as the materials. Under the condition of a total nitrogen application rate of 300 kg/hm², three kinds of nitrogen management methods were applied, N₁: a seedling: tiller: panicle: grain ratio of 30%:50%:13%:7%; N₂: a ratio of 20%:40%:30%:10%; and N₃: 10%:30%:40%:20%. Their effects on root morphology, root architecture, and nitrogen metabolism enzyme activities were studied. The results showed, drip irrigated rice yields were highest under W₁N₂, reaching 9.0 t/hm² for T-43 and 7.3 t/hm² for LX-3. Compared with W₂, the root length density (RLD), surface area density (SAD), and root volume density (RVD) of finely branched roots, coarsely branched roots and adventitious roots increased by 49.5%, 44.6%, and 46.7%; the RLD, SAD, RVD, and root architecture RLD β values of the 0–30-cm soil layer increased significantly (p < 0.05); and the yield and nitrogen partial factor productivity increased by 20.7% and 23.3%, respectively, under W₁. Compared with N₁, RLD, SAD and RVD in 0–10 cm soil layer under N2 increased significantly by 24.8%, 35.6% and 31.4%, and RLDβ decreased significantly (p < 0.05); Leaf GS, GOGAT and GDH were increased by 37.9%, 17.0% and 40.9%; all indexes showed a downward trend under N₃. Compared with LX-3, T-43 RLD, SAD, RVD increased significantly (p < 0.05), nitrogen metabolism enzyme activity increased, and yield increased by 21.8%. Rational water and nitrogen management can optimize the root growth and distribution characteristics and achieve simultaneous improvement of rice yield, nitrogen absorption, and nitrogen utilization efficiency under drip irrigation. Full article

Ammonia (NH₃) volatilization from paddy fields is a major issue which leads to poor fertilizer use efficiency and is considered a severe threat to the atmosphere. The previous research studies gave importance to the use of nitrogen fertilizers to mitigate NH₃ volatilization, while very little emphasis was given to the role of other fertilizers, such as phosphorus (P), for the alleviation of NH₃ volatilization in rice fields. Considering P importance herein, we conducted two consecutive field experiments using an innovative, controlled-release, phosphorus-blended fertilizer (CRPBF, with levels CRP0, CRP1, and CRP2). We compared CP0 (in which no fertilizer was applied), CP1 (112.5 kg P ha⁻¹ P of locally recommended fertilizers), and CP2: (P and K blended fertilizers) to determine the best possible way to reduce NH₃ volatilization without affecting the yield and quality of rice. The results of the study suggested that the yield of rice increased significantly with the application of CRP1 (11.11 t ha⁻¹) and CRP2 (11.99 t ha⁻¹). The addition of CRP1 and CRP2 to the rice field also enhanced yield-related components, i.e., panicle weight, total spikelets per unit area, spikelets per panicle, and above-ground biomass. CRP0 showed a lower yield and related components when compared to CP2. The addition of CRP1 and CRP2 demonstrated lower protein contents when compared to other treatments. The CRPBF application improved starch content and taste scores, and reduced the chalkiness of the rice grain during both years. The results showed a decreasing trend in NH₃ volatilization from CRPBF amendments by improving the nitrogen use efficiency traits when compared to other treatments: CRP2, CRP1, and CRP0 reduced NH₃ volatilization by 45%, 35%, and 15%, respectively. The results of this study indicate that, due to the episodic nature of NH₃ volatilization, CRPBFs with 50% P and 100% P can markedly reduce NH₃ volatilization from paddy fields without compromising the yield and quality of the crop, and could be a promising alternative to the ordinary commercial fertilizers used in rice fields. Full article

The tuberose, Agave amica, is an ornamental plant appreciated for its oils. The objective of this study was to evaluate the effect of planting dates (April, May and June), dose of NPK (N₈₀-P₆₀-K₄₀, N₃₀₀-P₂₀₀-K₂₀₀, N₁₀₀-P₅₀-K₅₀ and N₀₀-P₀₀-K₀₀), and fertilizer sources (chemical, organic, combined and control) on tuberose production, flower quality and postharvest shelf life. The physiological variables spike characteristics, leaf color, biomass, and postharvest flower quality were evaluated. The results show that the best planting date is in June; plants planted in June flowered earlier (156 days) and had better flower quality. The fertilization formula N₃₀₀-P₂₀₀-K₂₀₀ produced a higher number of spikes (1.32) and flowers (38.93), a larger stem diameter (0.9 cm), and promoted fewer days to flowering (188d). Plants fertilized with chemical fertilizer had fewer yellow leaves, a larger number of spikes (1.41), a longer spike length (26.89 cm), and a higher number of flowers/spikes (39.28), corms/plants (31.03), and open flowers on the ninth day in vase (13.14) and heavier stems with spikes (134.80 g). In conclusion, the dose of N₃₀₀-P₂₀₀-K₂₀₀ from chemical source and planting in June produced the best flower quality and the shortest production cycle. Full article

A reduced basal and increased topdressing fertilizer rate (RBIT) can usually increase rice yield, but whether this practice alleviates the impact of poor weather on rice production is unknown. Thus, the effect of three integrated RBIT treatments (RBITs, including RBIT alone, RBIT in combination with straw incorporation (RBITS) or a reduced fertilizer rate (RBITR)) on rice growth and nutritional status under different weathers was investigated in a 9-year experiment. Conventional fertilization (CF) was the control. We found that daytime temperature and light (DTL) after heading were the main meteorological factors limiting rice yield increases. RBITs did not affect rice yield under High-DTL, compared with CF, but RBITS significantly increased rice yield under Low-DTL. Compared with High-DTL, the positive effect of RBIT and RBITR on the N concentration and proportion in vegetative organs under Low-DTL was higher than the K concentration in vegetative organs, but RBITS showed the opposite trend. Regression analysis indicated that the harvest index had stronger correlations with the N concentration (negative), K concentration (positive), and N/K (negative) in vegetative organs under Low-DTL than under High-DTL. Our findings suggested that RBITS could improve rice adaptability to daytime temperature and light changes after heading by balancing crop nutritional status (N/K). Full article