Effects of biogas slurry addition on nitrogen， phosphorus， and potassium stoichiometry and feed quality of Pennisetum purpureum

doi:10.11686/cyxb2025427

Abstract

Abstract:

In this study， we investigated the effects of adding biogas slurry on the nutrient and feed quality of Pennisetum purpureum. Biogas slurry was applied to P. purpureum at five different rates （0， 50， 100， 150 and 200 kg N·ha^-1 per application， denoted as CK， N₅₀， N₁₀₀， N₁₅₀ and N₂₀₀， respectively） three times during a 45-day cutting cycle. The contents of nitrogen （N）， phosphorus （P）， potassium （K）， crude protein （CP）， neutral detergent fiber （NDF）， and acid detergent fiber （ADF） in stems and leaves were measured， and the effects of biogas slurry addition on CP， relative feeding value （RFV）， and the N， P and K stoichiometry of P. purpureum were analyzed. The results show that the addition of biogas slurry significantly increased the CP and N contents of P. purpureum stems （P<0.05）， and there were significant differences in responses among different cutting periods and different organs （P<0.001）. The N₅₀ treatment led to a significant reduction in the ADF content in the leaves at the second cutting （P<0.05） and significant differences in ADF contents among different organs （P<0.001）. At the second cutting， the RFV of leaves was highest in the N₁₀₀ treatment， and was significantly higher than that in the N₂₀₀ treatment （P<0.05）. There was a significant positive correlation between CP and RFV. Both CP and RFV were significantly positively correlated with N， K， N∶P and K∶P in stems and N and P in leaves， and negatively correlated with NDF and ADF in both organs （P<0.05）. A stepwise regression analysis and structural equation model showed that the N contents of stems and leaves significantly and positively affected the CP content of P. purpureum （P<0.001）， with total effect values of 0.92 and 0.32， respectively. The stem P content and leaf K∶P and P content jointly affected RFV， with total effect values of -0.86， 0.59， and 0.57， respectively. In conclusion， application of biogas slurry affected the N and P contents of stems and leaves and the K∶P of leaves， thereby directly or indirectly regulating the feed quality of P. purpureum.

Key words: Pennisetum purpureum, biogas slurry, nitrogen， phosphorus and potassium, stoichiometric ratio, feed quality

Xiao-yun HUANG, Zheng-xiang LIANG, Zhi-feng WU, Liu-ting ZHOU, Chang-fu CHEN, Jia-li LIN, Tao LUO, Xiu-sheng HUANG. Effects of biogas slurry addition on nitrogen， phosphorus， and potassium stoichiometry and feed quality of Pennisetum purpureum[J]. Acta Prataculturae Sinica, 2026, 35(10): 167-179.

Figures/Tables 5

Fig.1 Total nitrogen， phosphorus， potassium content and stoichiometric ratio in stems and leaves of P. purpureum under biogas slurry application

Fig.2 The main forage quality indices in stems and leaves of P. purpureum under biogas slurry application

Fig.3 Correlation heat map between the content of total nitrogen， phosphorus， potassium and their stoichiometric ratios and the main forage quality indices in stems and leaves of P. purpureum

Table 1 Stepwise regression analysis of main forage indexes and total nitrogen， phosphorus， potassium content and stoichiometry in stems and leaves of P. purpureum

指标 Index	回归方程 Regression equation	R²	F	P
CP	Y_CP=0.773X_SN^*+0.281X_LN^*	0.883	110.118	<0.001
NDF	Y_NDF=36.444-0.679X_LK^*-0.365X_LP^*	0.879	106.779	<0.001
ADF	Y_ADF=45.658-0.757X_SK^***	0.557	37.479	<0.001
RFV	Y_RFV=98.455+0.689X_LK^*+0.350X_LP^*	0.874	101.297	<0.001

Fig. 4 Structural equation modelling （SEM） of biogas slurry influencing crude protein and relative feeding value of P. purpureum and the standardized effect values of each factor

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