Effect of inorganic fertilizers on forage yield, accumulation of carbon, nitrogen and phosphorus in sudangrass (Sorghum sudanense) and ryegrass (Lolium multiflorum) cropping system in Central China

Abstract

The sudangrass (Sorghum sudanense) and ryegrass (Lolium multiflorum L.) rotation is a new type of cropping system in central China. A field study of effects of inorganic fertilizers (NPK) on yield of forage, accumulation of C, N and P in grass and soil fertility in this rotation was conducted through a four-year field experiment from April 2005 to May 2009. The treatments consisted of control (CK), fertilizer P and K (PK), fertilizer N and K (NK), fertilizer N and P (NP) and fertilizer N, P and K combination (NPK). For four years, proper fertilization (NPK treatment) increased yield of sudangrass and ryegrass by 17.2%–23.1% compared to the NP treatment, increased by 20.2%–26.8% compared to the NK treatment, and were 2–4 times higher than that of CK and PK treatments. The accumulation of C, N and P in NP (fertilizer N, P), NK (fertilizer N, K) and NPK (fertilizer N, P, K) treatments were 118.8%–173.5%, 269%–468% and 48.7%–157.5% higher than those of the CK treatment, respectively, while PK treatment was similar to CK treatment. At the end of the experiment, organic C, total N and P in soil in the NPK treatment were 14.6%, 18.4%, 36.6% higher than those of the CK treatment, respectively. The proper combination of NPK fertilizers could assure crop yield and sustainable soil productivity