Fertilizer 15N balance in a soybean–maize–maize rotation system based on a 41-year long-term experiment in Northeast China

Abstract

Global awareness of the need to enhance crop production and reduce environmental issues associated with nitrogen (N) fertilizer has increased. However, studies on how the N fate changed with manure addition are still limited. To explore efficient fertilization management for an improved grain yield, N recovery efficiency, and reduced N residual in the soil or that unaccounted for, a field 15N micro-plot trial in a soybean–maize–maize rotation was conducted to evaluate the effect of fertilization regimes on soybean and maize yields and the fertilizer N fate in the plant–soil system during 2017–2019 within a 41-year experiment in Northeast China. Treatments included chemical N alone (N), N and phosphorus (NP), N, P, and potassium (NPK), and those combined with manure (MN, MNP, and MNPK). Application of manure increased grain yield, on average, by 153% for soybean (2017) and 105% and 222% for maize (2018 and 2019) compared to no manure, with the highest at MNPK. Crop N uptake and that from labeled 15N-urea also benefited from manure addition, mainly partitioned to grain, and the average 15N-urea recovery was 28.8% in the soybean season with a reduction in the subsequent maize seasons (12.6%, and 4.1%). Across the three years, the fertilizer 15N recovery ranged from 31.2–63.1% (crop) and 21.9–40.5% (0–40 cm soil), with 14.6–29.9% unaccounted for, including N losses. In the two maize seasons, manure addition significantly increased the residual 15N recovery in crop attributed to the enhancing 15N remineralization, and reduced that in soil and unaccounted for compared to single chemical fertilizer, with MNPK performing the best. Therefore, applying N, P, and K fertilizers in the soybean season and NPK combined with manure (13.5 t ha–1) in the maize seasons is a promising fertilization management strategy in Northeast China and similar regions.

Enhancing Soybean and Maize Yields through Improved Nitrogen and Soil Water Use Efficiencies: A 40-Year Study on the Impact of Farmyard Manure Amendment in Northeast China

“…However, excessive N application could lead to soil nitrate N accumulation, promoting nitrate N leaching in the deeper soil layers, making the use of nutrients more difficult for crops [ 45 , 46 , 47 ]. The results of our previous study, which involved 15 N tracing in the same experiment, indicated that the N use efficiency during the soybean season was only 28.8% [ 11 ] and that during the maize season was lower, standing at 12.6% (unpublished data). This not only increased N loss but also resulted in adverse effects such as nitrate groundwater contamination and soil acidification [ 48 , 49 ].…”

“…The N, P, and K fertilizers were applied as urea, superphosphate, and potassium sulfate, respectively, and the organic fertilizer was pig manure. The average nutrient concentrations of the pig manure from the past 40 years were as follows: 83.5 g kg −1 organic carbon, 8.7 g kg −1 P 2 O 5 , and 10.0 g kg −1 K 2 O [ 10 , 11 ]. Table 1 shows the application rates of chemical and organic fertilizers in the soybean and maize seasons.…”

“…The application of chemical fertilizer combined with manure is an effective way to increase crop yield and improve soil fertility [ 9 , 10 , 11 ]. In Jilin, China, a long-term experiment showed that the application of N, phosphorus (P), and potassium (K) fertilizers combined with manure significantly increased maize yield by 159 kg yr −1 and the soil total N by 0.029 g kg −1 yr −1 compared to the unfertilized treatment [ 12 ].…”

Optimal Planting Density and Nutrient Application of Soybeans: A Case Study in Northeastern China

“…1 of 2022 proposes to vigorously implement the soybean and oilseed production capacity enhancement project. The agricultural sector has increasingly prioritized collaboration with agricultural institutions for experiments related to crop cultivation and fertilization [2,3], with a particular focus on major grain crops like soybeans [4], maize [5], rice [6,7], and wheat [8], especially within the context of planting and fertilization experiments. According to the 2020 statistics from the Food and Agriculture Organization (FAO) of the United Nations, global agricultural fields received a total application of 85 million metric tons of nitrogen (N), 7 million metric tons of phosphorus (P), and 12 million metric tons of potassium (K).…”