Effects of nitrogen reduction combined with organic fertilizer on growth and nitrogen fate in banana at seedling stage

Digestate-based organic amendment substitution improves the red soil quality and pakchoi yield

This study investigated the effect of the partially substituting chemical fertilizers (CF) with digestate-based organic amendment (OA) on the amelioration of red soil and the growth of plant. OA with nitrogen substitution rates ranging from 10 % to 40 % were mixed with CF and applied to red soil in a pot experiment. The results indicated that plant growth was significantly enhanced in the treatment where 20 % of the CF was substituted with the OA (OA20) compared to other treatments (p < 0.05). Specifically, the OA20 treatment increased nutrient use efficiency by 54.76 %-100.42 % compared to the treatment using only CF. Furthermore, all OA treatments improved the quality of red soil, with the nutrient content significantly higher in the OA20 group than in the other treatments (p < 0.05). The parameters of total phosphorus (TP), available nitrogen (AN), available phosphorus (AP), and total potassium (TK) significantly affected the soil quality index and plant growth, serving as reliable indicators of soil quality and plant yield. Microbial analysis revealed that the bacterial Chao index and the abundance of microorganisms involved in C-N nutrient cycling, such as Chryseolinea and norank_f__norank_o__Actinomarinales, were highest in the OA20 group. Significant correlations were observed between soil nutrient content (AN, AP, and TK) and the abundance of norank_f__norank_o__Actinomarinales and Chryseolinea, indicating their close relationship with pakchoi growth. Consequently, digestate-based OA may positively affect plant growth in acidic ecosystems by enhancing soil properties, inducing shifts in microbial community composition, and promoting the enrichment of potentially beneficial bacteria. This study provides valuable insights for the enhancement of low-quality soils and the resource utilization of digestate.

Nondestructive estimation of leaf chlorophyll content in banana based on unmanned aerial vehicle hyperspectral images using image feature combination methods

Introduction

Nondestructive quantification of leaf chlorophyll content (LCC) of banana and its spatial distribution across growth stages from remotely sensed data provide an effective avenue to diagnose nutritional deficiency and guide management practices. Unmanned aerial vehicle (UAV) hyperspectral imagery can document abundant texture features (TFs) and spectral information in a field experiment due to the high spatial and spectral resolutions. However, the benefits of using the fine spatial resolution accessible from UAV data for estimating LCC for banana have not been adequately quantified.

Methods

In this study, two types of image features including vegetation indices (VIs) and TFs extracted from the first-three-principal-component-analyzed images (TFs-PC1, TFs-PC2, and TFs-PC3) were employed. We proposed two methods of image feature combination for banana LCC inversion, which are a two-pair feature combination and a multivariable feature combination based on four machine learning algorithms (MLRAs).

Results

The results indicated that compared to conventionally used VIs alone, the banana LCC estimations with both proposed VI and TF combination methods were all significantly improved. Comprehensive analyses of the linear relationships between all constructed two-pair feature combinations and LCC indicated that the ratio of mean to modified red-edge sample ratio index (MEA/MSRre) stood out (R 2 = 0.745, RMSE = 2.17). For multivariable feature combinations, four MLRAs using original or two selected VIs and TFs-PC1 combination groups resulted in better LCC estimation than the other input variables. We concluded that the nonlinear Gaussian process regression model with the VIs and TFs-PC1 combination selected by maximal information coefficient as input achieved the highest accuracy in LCC prediction for banana, with the highest R 2 of 0.776 and lowest RMSE of 2.04. This study highlights the potential of the proposed image feature combination method for deriving high-resolution maps of banana LCC fundamental for precise nutritional diagnosing and operational agriculture management.

The impact of the combined application of biochar and organic fertilizer on the growth and nutrient distribution in wheat under reduced chemical fertilizer conditions

Organic fertilizer can help replenish fertility in cropland and reduce the use of chemical fertilizers, with biochar is an important soil conditioner. Under the premise of chemical fertilizer reduction, whether the application of biochar and organic fertilizer affect the yield and nutrient absorption and utilization of wheat? In this experiment, 7 treatments were set up in a randomized field trial with each treatment repeated three times: (1) CK1: no fertilizer; (2) CK2: 100% inorganic fertilizer; (3) T1: recommended amount of biochar with 100% inorganic fertilizer; (4) T2: recommended amount of organic fertilizer with 80% inorganic fertilizer; (5) T3: recommended amount of organic fertilizer and biochar with 80% inorganic fertilizer; (6) T4: recommended amount of organic fertilizer with 60% inorganic fertilizer; and (7) T5: recommended amount of organic fertilizer and biochar with 60% inorganic fertilizer. The results of this study showed that biochar combined with organic fertilizer can reduce the amount of chemical fertilizer by 40%~20% while ensuring wheat yield. Combining the input and output, 80% inorganic fertilizer with biochar and organic fertilizer (T3) was recommended. Under this fertilization scheme, the wheat yield was 37.32% higher than that of 100% chemical fertilizer (CK2), and the photosynthetic capacity was 54.97% higher at seedling stage. At the tillering stage, the root nitrogen content of T3 was significantly higher than that of T2, T4 and T5, which was 21.44%, 54.63% and 60.16%, respectively. The nitrogen content of T3 was significantly higher than that of other treatments at maturity, and the nitrogen content of T3 was 4.38% higher than that of CK2. At heading stage, the nitrogen allocated to T3 leaves was 4.71% higher than CK2. Overall, the results of this study showed that the combination of biochar and organic fertilizer could effectively reduce the application of chemical fertilizer. The recommended fertilizer regimen was 80% inorganic fertilizer with biochar and organic fertilizer, under this scheme, wheat had stronger photosynthetic capacity and better nutrient absorption and distribution mechanism.

Impacts of MnO2 on tomato (Lycopersicon esculentum Mill.) growth: A study with MnO2-amended organic fertilizer

Manganese dioxide (MnO2), as a catalyst in composting processes, can accumulate in soil over multiple fertilizations. However, its impact on crop growth remains to be explored. In this study, a pot experiment was conducted to investigate the impacts of MnO2 on the tomato plant performance across various growth stages. Results showed that MnO2 reduced the plant height, leaf number and length by 35.53 %, 27.61 %, and 37.00 %, respectively, and decreased the fruit weight (23.16 %) and sugar-acid ratio (29.7 %) of fruits compared to the MnO2-free control. The adverse impacts of MnO2 on plant growth might be attributed to the inhibition of microbial activity in soil reflected by the reduction of soil urease (9.30 %) and acid phosphatase (12.52 %) activities, which decreased the efficiency of nutrients conversion and uptake. The decrease of nutrient elements in roots resulted in oxidative stress in the plant, inhibiting the plasma membrane H+-ATPase activity thereby reducing the translocation of nutrients (e.g., calcium, magnesium, and phosphorus) translocation from roots to leaves. Furthermore, the phytohormones indolebutyric acid, gibberellin, and jasmonic acid of leaves were disturbed. This study reveals the risks associated with the application of MnO2-containing organic fertilizers.

Short-term high-temperature pretreated compost increases its application value by altering key bacteria phenotypes

Short-term high-temperature pretreatment can effectively shorten the maturity period of organic waste composting and improve the fertilizer efficiency and humification degree of products. To investigate the effect and mechanism of the end products on the saline-alkali soil improvement and plant growth, the short-term high-temperature pretreatment composting (SHC) and traditional composting (STC) were separately blended with saline-alkali soil in a ratio of 0-40 % to establish a soil-fertilizer blended matrix for cultivating Lolium perenne L. The pot experiments combined with principal component analysis showed Lolium perenne L. planted in 20 % SHC-blended saline-alkali soil had the best growth effect, and its biomass, chlorophyll content, and plant height were 109-113 % higher than STC. The soil physicochemical property analysis showed that SHC and STC increased the soil nutrient content, humification degree, and enzyme activity at any blending ratio. The microbial analysis showed that 20 % SHC in the saline-alkali soil stimulated the growth of functional microorganisms and the addition of SHC promoted the sulfur cycle, nitrogen fixation, and carbon metabolism in the soil-plant system. The correlation analysis showed that pH; nutrient contents; and urease, catalase, sucrase, and phosphatase activities in the saline-alkali soil were significantly correlated with plant growth indexes (p < 0.05). Georgenia and norank_f__Fodinicurvataceae had a stronger correlation with four types of enzyme activities (p < 0.01). SHC improved the saline-alkali soil and promoted plant growth by adjusting soil pH, increasing soil nutrients, and influencing soil enzyme activity and dominant flora. This study provides a theoretical basis for applying SHC products in soil improvement.

Biogas slurry topdressing as replacement of chemical fertilizers reduces leaf senescence of maize by up-regulating tolerance mechanisms

Worldwide physiological research has aimed to decelerate the aging of crop leaves by optimizing fertilization measures to improve crop or biomass yield. Solid organic fertilizers can be combined with chemical fertilizers to delay the aging of crop leaves. Biogas slurry is a liquid organic fertilizer produced by the anaerobic fermentation of livestock and poultry manure and other resources, and it can partially replace chemical fertilizers in field application via drip irrigation systems. However, the impact of biogas slurry topdressing on leaf aging remains unclear. This study investigated treatments with no topdressing (control, CK) and five topdressing patterns of biogas slurry replacing chemical fertilizer (nitrogen) at 100%, 75%, 50%, 25%, and 0% (100%BS, 75%BS, 50%BS, 25%BS, CF). The effects of different proportions of biogas slurry on leaf senescence rate, photosynthetic pigments, osmotic adjustment substances, antioxidant defense enzymes, and nitrogen metabolism related enzyme activities of maize were analyzed. Subsequently, the mechanisms of biogas slurry topdressing on the leaf senescence rate of maize were explored. The results showed that the mean decreasing rate of relative green leaf area (Vm) treated with biogas slurry decreased by 3.7%-17.1% and the duration of leaf area duration (LAD) increased by 3.7%-17.1% compared with the results for CK. The maximum senescence rate of 100%BS was delayed by 4.4 and 5.6 d compared to the results for CF and CK, respectively. During the senescence of maize leaves, the use of biogas slurry topdressing increased the content of chlorophyll, decreased the water loss and the accumulation rate of malondialdehyde and proline in leaves, and increased the activities of catalase, peroxidase, and superoxide dismutase in the later growth and development periods of maize. In addition, biogas slurry topdressing improved the nitrogen transport efficiency of the leaves and ensured continuous and efficient ammonium assimilation. Furthermore, there was a strong correlation between leaf senescence and the investigated physiological indices. Cluster analysis showed that the 100%BS treatment exhibited the most prominent effect on leaf senescence. Biogas slurry topdressing as a substitute for chemical fertilizer can be potentially used as an anti-aging regulation measure for crops to decrease the damage induced by senescence.

Effects of Co-Digestion Sludge Application on Soil Productivity

Anaerobic digestion and agricultural use of sewage sludge are effective methods to treat and dispose of sewage sludge, respectively. Then, the anaerobic digested sewage sludge is applied in agricultural land and the improvement of soil properties can be expected. In this study, with the purpose of evaluating the potential of co-digestion sludge for agricultural use, plot experiments with two vegetable species (radish and Chinese cabbage) and three application dosages were carried out in a short term of six months. Focus was on soil physical properties, soil nutrient change and plant growth responses during the whole process. Results showed that application of co-digestion sludge had little effect on soil physical properties, including the bulk density, porosity, capillary porosity and non-capillary porosity. However, after the application of co-digestion sludge, the maximum increase in content of organic matter, total nitrogen, hydrolysable nitrogen, total phosphorus and available phosphorus in soil reached 51%, 125%, 212%, 15% and 87%, respectively, which supplied the available nutrients quickly and continuously. The application of co-digestion sludge promoted the growth of radish and Chinese cabbage, which was observed through increase of the leaf, root biomass and plants height. Consequently, co-digestion sludge has a good application prospect for improving soil productivity as fertilizer.