Long-Term Mineral Fertilization Improved the Grain Yield and Phosphorus Use Efficiency by Changing Soil P Fractions in Ferralic Cambisol

Waqas Ahmed,Huimin Zhang,Qinghai Huang,Jing Huang,Rana Muhammad Ammar Asghar,Sajid Mehmood,Sehrish Ali,Yongmei Xu,Muhammad Qaswar,Kailou Liu,Mohsin Mahmood

doi:10.3390/agronomy9120784

Abstract

Elevated mineral fertilization may change the composition and increase the availability of soil phosphorus (P) in subtropical paddy soils and thus affect long-term plant growth. However, an understanding of the response of soil P fractions to long-term nitrogen, phosphorus and potassium (NPK) additions remains elusive. This study aimed to explore the responses of soil P-fractions and their mobility to different long-term chemical fertilization rates under a double rice cropping system. The rates of nitrogen (N), phosphorus (P), and potassium (K) in the low NPK treatment (LNPK) were 90, 45, and 75 kg ha−1 year−1, respectively, and in the high NPK treatment (HNPK), they were 180, 90, and 150 kg ha−1 year−1, respectively. The results showed that the concentrations of soil organic matter (SOM), total P, Olsen P, total N, and mineral N were remarkably increased under HNPK by 17.46%, 162.66%, 721.16%, 104.42%, and 414.46%, respectively, compared with those under control (CT). Compared to the CT P fractions, HNPK increased the labile P fractions (i.e., NaHCO3-Pi and NaHCO3-Po) by 322.25% and 83.53% and the moderately labile P fractions (i.e., NaOH-Pi, NaOH-Po and HCl. dil. Pi) by 163.54%, 183.78%, and 3167.25% respectively, while the non-labile P was decreased by the HNPK addition. P uptake and grain yield were increased by LNPK and HNPK by 10.02% and 35.20%, respectively, compared with CT. P use efficiency indices were also higher under HNPK than under LNPK. There was a strong positive relationship between grain yield and P use efficiency (R2 = 0.97). A redundancy analysis (RDA) showed a strong correlation between soil chemical properties and the labile and moderately labile P pools. Structural equation modeling (SEM) revealed that SOM, mineral N, and available P strongly control the labile P pool. In conclusion, NPK additions under the paddy soils significantly influences the soil P fractions. The soil P dynamics and the mechanisms governing the interactions between plants and soil nutrients are clearly explained in this study.

Highlights

Phosphorus (P) is considered one of the nutrients with highest demand and plays a vital role in plant growth
Structural equation modeling (SEM) significantly explained the effects of soil organic matter (SOM), mineral N, and available P on P pools and uptake in the paddy soil (Figure 6)
Available P showed a direct effect on the moderately labile P. These results are in accordance with Jimenez et al [59] who stated that the SOM and the soil P could be the key factors affecting P mobility and transformations in the paddy soils

Summary

Introduction

Phosphorus (P) is considered one of the nutrients with highest demand and plays a vital role in plant growth. The accessibility of phosphorus in the soil depends on the various P-fractions that influence the primary production of agricultural ecosystems [1]. Under long-term fertilization, phosphorus becomes unavailable for plant uptake as it becomes fixed and precipitated with aluminum, calcium, and iron in soil [2,3,4] which results in non-labile P formation [5]. The major problem associated with P fertilizer application is the low efficiency of P uptake by the plants. Nitrogen is a prime element for attaining consistently high crop production [6]. The interaction of P with nitrogen (N) could be considered the most essential nutrient interaction in practical terms [7]

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