Objective We investigated the nutrient release characteristics of landscape waste organic fertilizer (LWOF) and the effect of its application on Pinus tabulaeformis, aiming for the scientific use of LWOF as an organic fertilizer in the management of artificial forest.

Method The nylon net bag method was adopted to study the nutrient release of LWOF. Dry LWOF samples of 50 g was loaded into nylon bags (8.47 μm) and buried into 0−20 cm and 20−40 cm soil layers, respectively. The samples were collected every one and half month for the analysis of residual LWOF and the corresponding organic matter and NPK in them, and the residual rate was then calculated. Field experiment was conducted for the promotion effect of LWOF in sandy area of Beijing plain, the test Pinus tabulaeformis forest was camped in 2015. Six application amounts of LWOF were set up for the research, including 0, 10, 15, 20, 25, and 30 kg/plant, denoted as CK, T1, T2, T3, T4, and T5, respectively. Soil physicochemical properties at the beginning and one year after experiment were determined, and the growth indicators of the Pinus tabulaeformis were investigated at the same time.

Results 1) The decomposition rate of LWOF buried in 20−40 cm soil layer was faster than in 0−20 cm soil layer. The residue rates of organic matter in 0−20 cm and 20−40 cm layers of LWOF after 6 months of decomposition were 52.46% and 48.72%, respectively. The N in LWOF was gradually released during the 6-month period, with the last residue rate of 58.73% and 56.93%, respectively. P was released rapidly in the first 1.5 months of burial and then fluctuated, with the last residual rates of 52.23% and 52.15%, respectively. The release of K was rapid and relatively complete, with the residual rates of 27.95% and 28.54% in the first 1.5 months and the last residue rate of 22.73% and 20.89% after 6 months. 2) One year after the application of LWOF, the organic matter content increased significantly, the soil total N in T4 treatment in 0−20 cm soil layer was 41.81% higher, the available P content in 0−20 cm layer under T4 was 53.13% higher, the easily available K content in 20−40 cm layer under T5 treatment was 1.63 times of that of CK. 3) The highest tree height was recorded in T3 treatment, the largest wood volume in T1 treatments, and the highest leaf nutrient contents in T4 and T5 treatments. The chlorophyll a, b, and a+b content increased first and then decreased with the increase of LWOF rate, with the peak values in T4 treatment, and the increase rate of 81.25%, 85.71%, and 90.00% over CK, respectively. 4) The positive effect on the growth and nutrient indexes of Pinus tabulaeformis was in order of T4>T5>T3>T1>T2>CK.

Conclusion The decomposition rate of LWOF in 20−40 cm soil layer is faster than in 0−20 cm layer. When buried in soil, the N in LWOF is released gradually, and P is released quickly at first one and half months, and more than half of N and P will be released within 6 months, while K will be released more quickly and completely, compared to N and P. The application of LWOF shows satisfactory effect in improving soil fertility and tree growth, and the recommended application rate on Pinus tabulaeformis is 25 kg/plant.