Impact of no-tillage and reduced nitrogen input on corn yield and nitrogen efficiency in the corn belt of northeast China

Abstract

Context

Conservation tillage is widely used in northeast China to improve soil fertility and crop yields. However, the specific mechanisms behind stable and increased corn yields and the role of nitrogen fertiliser under no-tillage with reduced nitrogen input remain unclear.

Objective

This study aimed to elucidate the mechanisms behind stable and increased corn yields and the contribution of nitrogen fertiliser under no-tillage practices with reduced nitrogen input.

Methods

Field experiments were conducted from 2021 to 2023, involving four tillage treatments: rotary tillage without straw mulching as control treatment (RT), direct seeding on stubble fields without flat-lying residue (DS), no-tillage with straw mulching on wide inter-row spaces (NTW), and no-tillage with straw mulching across the entire field (NTE). Nitrogen treatments were applied to the NTW and NTE plots, consisting of 260 kg N hm⁻² (100 % farmer practice, N2), 195 kg N hm⁻² (75 % farmer practice, N1), and 0 kg N hm⁻² (no nitrogen input).

Results

Fertiliser contributed 40 %–75 % to corn yield, inherent soil productivity contributed 25 %–60 %, nitrogen input 29 %–42 %, and straw mulching 0.3 %–16.7 %. The contribution percentage of inherent soil productivity (CPISP) in the no-nitrogen treatment was 2–4 times higher than in other treatments, with the fertiliser contribution rate (FCR) being 3–14 times higher in treatments with that nitrogen input. Compared to N2 treatments, N1 treatments significantly improved nitrogen use efficiency (NUE), nitrogen contribution rate (NCR), and partial factor productivity of nitrogen (PFPN) by 17 %–48 %, 29 %–42 %, and 16 %–45 %, respectively, without significantly affecting yield and net income. Corn yields in N1 and N2 treatments were 14 %–504 % and 22 %–128 % higher than in N0 treatments. Total and net incomes in the N1 and N2 treatments were 1.2–6 times and 1.1–21 times higher than in the N0 treatments. N1 treatments increased plant nitrogen uptake by 3 %–195 %, nitrogen residues by 44 %–67 %, and apparent losses by 10 %–40 %, with enhancing NUE. Compared to RT and DS treatments, NTW and NTE treatments increased corn yield by 0.3 %–16.7 %, reduced total inputs by 7 %–8 %, and improved net income by 3 %–26 %. Straw mulching increased relative soil water content, mineralised nitrogen(AN), Olsen-P, available potassium(AK), total nitrogen (TN) and soil organic matter (SOM) by 0.06 %–37.05 %, 0.2 %–352 %, 5 %–64 %, 2 %–24 %, 0.3 %–95.0 %, 0.1 %–40 %, respectively, leading to higher corn yields. The NTEN2 treatment resulted in the highest SOM, 5 %–15 % greater than other treatments. The DS and NTEN2 treatments achieved the highest corn yields without fertiliser application, with AK and TN in the N2 treatment being higher than in the N1 treatment by 4 %–28 % and 5 %–15 %, respectively. Structural equation modelling (SEM) showed that the average contribution of the above factors to yield was 80.5 % and identified nitrogen fertiliser as the most significant positive factor, with mineralised nitrogen of the first and third positions as the most significant soil factor affecting corn yield.

Conclusions

The findings suggest that reduced nitrogen input under no-tillage practices can maintain soil fertility, improve NUE, and sustain stable corn yields, offering a sustainable agricultural strategy for the corn belt of northeast China.