Slow-release performance is one of the most important indicators for the quality of fertilizers in fields. However, the common defects of fertilizers cannot fully meet the large-scale production in recent years, such as the low utilization rate, large amount of runoff leaching and nutrient volatilizing loss, as well as the difficult synchronization of nutrient release and crop absorption. In this study, thermal modification treatment was carried out on the high-quality slow-release material attapulgite combined with biochar material at 300℃. A heat-modified attapulgite-biochar composite was prepared to explore the release of nitrogen (N), phosphorus (P), and potassium (K). The biological properties of materials were verified with four seasons of Chinese cabbage. Seven treatments included: fertilizer + attapulgite (AF), fertilizer + thermal modified attapulgite (TAF), fertilizer + biochar (BF), fertilizer + attapulgite + biochar (ABF), fertilizer + thermal modified attapulgite + biochar (TABF), and no fertilizer (CK), where the ordinary fertilizer (F) was used as the control. The results show that: 1) The natural attapulgite was achieved in the better adsorption capacity for the N, P, and K elements after modification at 300℃. The modified attapulgite structure was broken with circular collapse, where there were a lot of gaps and cracks. 2) The combination of attapulgite and biochar enabled the structure of biochar particles from the lamellar to loosely porous, thus effectively preventing the agglomeration of biochar particles to dispersed evenly. Thermally modified attapulgite + biochar shared more channels and deeper pore size, compared with the biochar. As such, more sites were offered for the interaction between nutrient ions and composite materials. The SiO₂, MgFe₄(SO₄)₆(OH)₂(H₂O)_20, and CaMg(CO₃)₂, oxygen-containing groups improved the adsorption efficiency of composite adsorbent. 3) The slow release of nutrients was better achieved in TABF, compared with pure fertilizer. The peak of N and P nutrient release occurred on the 52th, and 42th day, respectively. 4) TABF can be expected to fully meet the nutrient supply requirements in the whole growth period of Chinese cabbage, which was superior to control and pure fertilizer treatment in the phenotypic indexes, quality, and yield. Five slow-release fertilizers significantly increased the utilization rate of NPK fertilizer and agronomic efficiency. TABF was the best, compared with common fertilizers. Therefore, 300℃ of thermal modification significantly improved the adsorption site of attapulgite. The biochar mixture can be expected to obtain the structure of the slow-release composite material with attapulgite-biochar as the core, in order to enhance the interaction with nutrient ions, and then effectively improve the slow-release performance of fertilizer. The finding can provide a strong reference to improve the utilization rate of N, P, and K fertilizers.

Biodegradable plastic film provides a new way to solve “white pollution”. However, there is an urgent need to solve the problems of residual plastic film and tail vegetable pollution after planting. Currently, the continuous degradation of polyethylene plastic film and biodegradable plastic film after returning to the field and their impact on soil environment and vegetable crop growth need further research. This study is expected to provide some theoretical support through residual membrane addition experiments. We uniformly buried PBAT/PLA humic acid biodegradable film (BIO1), PBAT/PLA-lignin biodegradable film (BIO2), and polyethylene film (PE) at 200 kg film residue per ha in potted soil. After burial 120 d, the crystallinity of BIO1 and BIO2 residue decreased by 7.37% and 3.91% respectively, compared to that of PE. Additionally, the water contact angle of BIO1 and BIO2 film was lower, and the weight loss rate significantly increased. Microplastics (polyethylene) abundance in the PE treatment substrate was (166.67 ± 169.96) n ·kg⁻¹ after 150 days of burial, and microplastics (PBAT/PLA) were not found in BIO1 and BIO2 treatments in this study. Residual film reduced the percentage of 2-1 mm and >2 mm water-stable agglomerates and increased the percentage of < 0.25 mm water-stable agglomerates, ledto soil compaction and water upward migration; reduced urease and sucrase activities in substrate, further reduced root vigor and increased leaf proline content, eventually reduced tomato yield. However, compared with PE, BIO1 have lower substrate volumetric weight, higher aeration porosity, alleviated soil compaction, stronger substrate enzyme activity and root activity, residues significantly increased soil Ascomycota relative abundance and decreased Zoopagomycota relative abundance; reduced leaf proline content, significantly increased tomato yield, and improved tomato quality by significantly increasing lycopene content by 12.80%. Overall, 200 kg · ha⁻¹ of residual humic acid biodegradable plastic film can improve tomato quality, reduce “white pollution”, and reduce microplastic residues caused by residual film in a solar greenhouse.