According to the specific conditions of the region, we sought to determine appropriate soil materials for improving soil conditions after the reclamation of hollow villages into cultivated land and for quickly restoring agricultural production.
Materials and methods
The test plot consisted of seven treatments with an area of 5 m?×?6 m (30 m2) each, and each treatment included three replicates. The plot was filled with raw soil (old wall soil) from an abandoned homestead in Yuzihe Village, Yaotou Town, Chengcheng County, Shaanxi Province, China. The test design was completely randomised with seven treatments: fly ash (T1), organic fertiliser (chicken manure) (T2), improver (ferrous sulphate) (T3), fly ash?+?organic fertiliser (T4), improver?+?organic fertiliser (T5), fly ash?+?improver (T6) and no fertilisation measures (T0). The modified materials were mixed evenly with raw soil then applied to a depth of 0–30 cm onto the test plot.
Results and discussion
After adding the various modified materials, the soil bulk density decreased by 6.52–14.49% and total soil porosity, capillary porosity and non-capillary porosity increased by 7.09–15.75%, 3.14–12.67% and 15.57–38.47%, respectively. The soil permeability coefficient increased by 5.75–10.75×. Organic matter, total nitrogen, available phosphorus and available potassium in reclaimed hollow village soil increased by 12.50–66.44%, 15.15–20.00%, 6.58–64.62% and 18.24–26.82%, respectively, relative to that of T0. Only T4, T2, T6 and T5 significantly increased maize yield and water use efficiency compared with T0. The other treatments did not significantly improve maize yield or water use efficiency.
Conclusions
Organic fertiliser and fly ash composite was an appropriate amendment for improving reclaimed soil in a hollow village in a loess hilly gully region.
To probe the effect of common coexist substances on the nitrate removal by polymeric resin supported nanoscale zero-valent iron composite (D201-nZVI), humic acid (HA) was added into the nitrate removal system to elaborate the different interactions between each two and among all in the system including HA, nitrate, and D201-nZVI. The results showed that the effect of HA on the reduction of nitrate by D201-nZVI was concentration-dependent. At low HA concentration (<?5 mg/L), HA coating formed by the HA adsorption on the surface of the nZVI particles enhanced the dispersion of the particles, which led to a more evenly distribution of nZVI particles in the solution, and thus a higher nitrate reduction activity. When HA concentration was increased to 5 mg/L or more, the competitive adsorption of HA and NO3? on the surfaces of the D201-nZVI dominated, and the nitrate removal rate and ammonia nitrogen production were decreased. When the HA concentration reached to a further high level (>?20 mg/L), HA acted as an electron shuttle to accelerate the reduction of Fe(III) to Fe(II) in the D201-nZVI, and thus the nitrate reduction rate was accordingly enhanced. The ammonia production increased by 24.8% at HA concentration of 40 mg/L as compared with that of the control (without addition of HA). This research elucidated the interaction of HA within different HA concentration in the complicate system of anions removal by organic support-nanoscale metal particle composite, which may shade some new light on the potential application of nanoscale zero-valent materials in the practical remediation of natural water. 相似文献