As and Cd in soil can be assimilated and accumulated by vegetables and can be subsequently ingested by humans. Contradictory effects of organic fertilizer application on As and Cd accumulation in soil have been reported in previous studies. An eight-year greenhouse study was conducted on a sandy loam soil in Beijing, China to investigate the effects of organic fertilizer application rate on soil properties, and As and Cd accumulation in soil. The contamination risk of pak choi grown after eight years’ application of organic fertilizer was also evaluated. Soil organic carbon increased 3.0–3.8 times with low, medium and high rates of fertilizer application in 2018 compared to the initial soil. Organic fertilizer application significantly increased soil nutrients and microbial biomass while it mildly affected soil pH. The bioavailability of As/Cd has decreased after eight years’ application of organic fertilizer. Pak choi crop harvested from all three treatments in 2018 did not pose a threat to human health, even for life-time consumption. Soil total As content significantly decreased with organic fertilizer application, mainly due to the lower As content in the applied fertilizer than that in soil. Continuous application of clean organic fertilizer can be adopted to reduce the contamination risk of highly contaminated soil in the soil–plant system.

During the summer months, greenhouse tomato production is challenged by the heat, causing yield reduction; therefore, we conducted a study to test the effectiveness of different foliar spray compositions for the improvement of Lycopersicon esculentum var. cerasiforme ‘Qianxi’ nutrition uptake and fruit yield. Two forms of silicon, two kinds of organic nitrogenous compounds and water as the control factor were two-two paired to become nine different recipes, which were as follows: CK (H ₂ O), ISi (K ₂ SiO ₃ ), organic silicon (OSi), potassium fulvate (BSFA), BSFA + ISi, BSFA + OSi, betaine (GB), GB + ISi and GB + OSi. The plants were sprayed three times during the period of the first, second and third truss fruit expansions with a 2-week interval. As a result, BSFA or K ₂ SiO ₃ generated higher yield in plants compared with the other compositions. Also, K ₂ SiO ₃ significantly enhanced the total nitrogen, phosphorus and potassium accumulation in fruit and the whole plant. Comparing across the nine recipes, BSFA + ISi, ISi and GB had improved the fruit yield by 17%, 12.7% and 9.5%, performing the best. BSFA + ISi, ISi and GB also improved the plant nitrogen uptake by 8.2%, 18.8% and 9.8%, as well as the potassium uptake by 16.2%, 12.3% and 15.2%, compared with CK, respectively. Thus, K ₂ SiO ₃ , BSFA and GB stimulated the plant nitrogen and potassium uptake, which improved the marketable yield.

The application of organic fertilizers is one of the most important agricultural measures aimed at improving the flavor and productivity of Lycopersicon esculentum, with the granulation and coating of organic fertilizers, which can reduce seepage losses of great significance to the ecosystem. In this study, Jingcai 8 tomato was selected as the test material. Headspace solid-phase microextraction and gas chromatography–mass spectrometry (HS-SPME-GC-MS) methods were used to investigate the effects of different pelletized organic fertilizers and various coating materials on the flavor profile of the tomatoes. The results indicated that 67 volatile organic compounds (VOCs) were identified in the tomato fruits and 62 volatile compounds were identified in the leaves under different fertilizer treatments. The volatile compound content of the fruits in the BP treatment group was 35.38 μg/g, which was higher than that in other treatment groups, and the volatile compound content of the leaves was lower. A differential compound analysis with log₂|fold change| ≥ 1 and variable important in projection (VIP) > 1 highlighted styrene, 3-methyl-1-butanol, and (E, E)-2,4-hexadienal as the major up-regulated compounds and methyl salicylate as the major down-regulated compound in the tomato fruit BCK (control) vs. BP. Moreover, the α-phellandrene content decreased in the tomato leaves. In addition, an analysis of the tomato fruit differential compounds and compounds with odor activity values (OAV) of ≥ 1, considering the OAV values of characteristic aroma compounds, identified key compounds affecting the flavor of the tomato fruits under the BP treatment. These included 2-nonenal, (E)-2-pentylfuran, trans-β-ionone, 1-penten-3-one, (E, E)-2,4-hexadienal, and 3-hexenol (fruity, floral, and herbaceous odors), (E, E)-2,4-heptadienal (fatty odor), and hexanal (green odor). The combined results analysis of the volatile compound content, differential compounds, and OAV values of characteristic aroma compounds aimed to clarify that the BP treatment group, which applied pelletized, large-grain organic fertilizer with polyurethane (pozzolanic + small-grain oil-coated + 2% paraffinic + 4% polyurethane) as a coating material, proved to be most effective in influencing the flavor of the tomato fruits. This finding lays the foundation for its potential commercial application in artificial orchards.