Rice plots treated with slow-release nitrogen fertilizer produced more grain and used energy more efficiently than plots under traditional fertilization in a randomized field experiment. The strongest performer was a treatment called DSU+PU, which combined side-deep slow-release fertilizer with 30% urea at the panicle stage. Compared with traditional fertilization, slow-release fertilizer treatments produced between 9,975.17 and 11,232.74 kilograms of grain per hectare, an increase of 10.65% to 23.54%. DSU+PU recorded the highest yield.
The distinction between treatments was important. One treatment, labeled DU, did not differ significantly from traditional fertilization, while the slow-release treatments delivered the reported yield gains. The result points to the specific combination tested, rather than to a blanket advantage for every nitrogen strategy. Here, that combination was DSU+PU.
The advantage was measured in energy, too
The yield result came with a broad improvement in the study's energy measures. Relative to traditional fertilization, slow-release treatments increased energy output by 10.38% to 22.98% and net energy by 11.11% to 24.68%. Energy-use efficiency rose by 9.62% to 22.40%, energy productivity by 8.88% to 22.86%, and energy profitability by 10.34% to 24.07%. Specific energy, another measure in the accounting, fell by 8.18% to 18.61%. DSU+PU showed the greatest gains and the lowest specific energy.
Those gains were not explained by a large drop in the amount of energy put into the system. Total energy input showed no substantial differences among the nitrogen-management practices. For the slow-release treatments, the reported input ranged from 26,918.69 to 27,628.29 megajoules per hectare. The analysis attributed the higher demand mainly to the energy needed to produce slow-release fertilizer, while the combined treatments used slightly less input than DSU.
What the trial counted
The energy balance covered the work and materials behind the crop. Machinery, fuel, electricity, irrigation, pesticides, fertilizers and labor were counted as inputs. Grain and straw were converted into energy equivalents on the output side, and removed straw was treated as a recoverable by-product. The reported energy figures therefore combine farm operations with the energy associated with the inputs used to produce the crop.
A tightly defined plot comparison
Researchers compared seven nitrogen-management treatments in a randomized complete block design. Three DSU-based treatments used 30% urea at the basal, tillering or panicle stage. Every nitrogen-fertilized treatment received 150 kilograms of total nitrogen per hectare. The design held the total nitrogen rate constant across fertilized treatments while varying the fertilizer form and timing.
The experiment used 21 plots, each measuring 19 square metres, with three replicate plots for every treatment. That structure makes this a replicated plot comparison, but it also keeps the evidence tied to the particular treatments and scale tested. The findings should be read as a comparison among these nitrogen strategies, not as a guarantee that the same ranking will hold whenever rice is fertilized differently.
A wider accounting, with clear boundaries
The researchers also monitored methane and nitrous oxide during all study seasons. They used static chambers and gas chromatography, taking repeated samples from the chamber headspace after closure. Carbon footprint was defined as a yield-scaled life-cycle measure that combined emissions linked to agricultural inputs with direct emissions from rice fields.
How the comparisons were tested
To test the comparisons, the analysis checked whether the data followed a normal pattern and whether the treatment groups had similar variance. It then used analyses of variance for individual years and for the combined data, with year and treatment treated as fixed factors and block treated as random. Pairwise least-significant-difference comparisons used a P value below 0.05 as the threshold for statistical significance.
What the result does, and does not, establish
The reported findings come with a defined level of uncertainty. The results give ranges and significance statements, but no confidence intervals or standard errors, so the size of the advantage cannot be pinned down more precisely from the supplied analysis. The DSU-based comparisons also fixed the urea supplement at 30% and used three application stages. They identify DSU+PU as the strongest of the tested options, not as a universal recipe.
Within that boundary, the result is clear. In these replicated rice plots, pairing side-deep slow-release fertilizer with panicle-stage urea produced the highest grain yield and the greatest gains across the reported energy measures, while slow-release treatments improved the comparison with traditional fertilization. That makes DSU+PU the leading option among the tested strategies, not a universal prescription for rice production.
Paper data and sources
Original title: Side-deep slow-release nitrogen fertilization combined with panicle-stage urea topdressing improves energy efficiency, reduces carbon footprint, and enhances economic performance in rice systems
Authors: Hu M, Li Z, Luo Y et al.
Journal/Repository: Frontiers in plant science
Status: Peer-reviewed
First online: 2026-10-08
DOI: Not available
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