Soil properties and carbon and nitrogen pools in a young hillside longan orchard after the introduction of leguminous plants and residues.

Huimin Xiang,Benliang Zhao,Yuan Zhang,Hui Wei,Jia-En Zhang

doi:10.7717/peerj.5536

Abstract

The intensification of young hillside Dimocarpus longan orchard cultivation has led to increase soil erosion and decrease soil fertility in South China. Leguminous crops are often used for improving soil properties. An approximately 2-year-long field experiment in lateritic soil in South China was conducted to evaluate the effects of legume introductions on soil properties and carbon (C) and nitrogen (N) pools. Two leguminous and one non-leguminous plant species, including Arachis hypogaea L. (a leguminous oilseed crop species, DA), Stylosanthes guianensis (a perennial herbaceous leguminous species, DS) and Lolium perenne L. (an annual non-leguminous forage species, DL), were introduced into a D. longan orchard as three treatments and compared to the monoculture of D. longan (the control, D0). And the harvested biomass residues of the three cover plants were returned to their corresponding plots as green manure. Soil samples were collected from depths of 0–10 and 10–20 cm approximately 2 years after treatment application. The results showed that, compared with D0, DA significantly improved the contents of soil available phosphorus, dissolved organic carbon (DOC), total nitrogen, ammonium and the N pool. In addition, DS significantly increased the contents of DOC, microbial biomass carbon and ammonium in the soil. However, DL did not affect any soil properties or the C and N pools. In addition, neither DA nor DS altered the soil bulk density or the contents of available nitrogen, total organic carbon and the C pool. The improvement of soil properties by DS and DA was positively correlated with the plant residues amount, plant N content but negatively correlated with the plant C:N ratios. Besides, the plant growth of longan was significantly improved by DA. In conclusion, compared with that of S. guianensis, the introduction of A. hypogaea L. was more helpful for restoring and improving soil properties, N pool and longan growth within the young hillside orchard in South China.

Highlights

Many hills and slopes are present in South China
To determine whether the introduction of leguminous species and their residues return improve soil fertility within young hillside orchards, we introduced two leguminous plant species (Arachis hypogaea L. and Stylosanthes guianensis) and one non-leguminous species (Lolium perenne L.) into a young hillside longan orchard in March 2015 and assessed the effects of these species introduction and residues return on soil nutrients and carbon (C) and N pools in a field experiment
Soil C and N pools The results showed that the introduction of plants into the young hillside orchards significantly affected the soil N pool in the subsurface soil layer (10–20 cm) (p < 0.05, Fig. 4B) but did not affect the soil C pool in the surface and subsurface soil layer

Summary

Introduction

The area of existing slope land in Guangdong Province is 13.51 Â 104 km, which accounts for 75.94% of the total land area (Zhuo et al, 2004). New orchards, especially those approximately 1–3-years-old, are often full of weeds due to hot and rainy climate during the spring in South China. Due to the high temperatures and rainfall in South China, soil erosion in this area is high. The eroded area of slope land in Guangdong Province is approximately 1.14 Â 104 km, which accounts for 79.74% of the total area of soil erosion in this province (Zhuo et al, 2004).

Methods

Discussion

Conclusion