Partial replacement of inorganic fertilizer with organic inputs for enhanced nitrogen use efficiency, grain yield, and decreased nitrogen losses under rice-based systems of mid-latitudes

Abstract

In the rice-based system of mid-latitudes, mineral nitrogen (N) fertilizer serves as the largest source of the N cycle due to an insufficient supply of N from organic sources causing higher N losses due to varying soil and environmental factors. However, aiming to improve soil organic matter (OM) and nutrients availability using the best environmentally, socially, and economically sustainable cultural and agronomic management practices are necessary. This study aimed to enhance nitrogen use efficiency (NUE) and grain yield in rice-based systems of mid-latitudes by partially replacing inorganic N fertilizer with organic inputs. A randomized complete block design (RCBD) was employed to evaluate the effects of sole mineral N fertilizer (urea) and its combinations with organic sources-farmyard manure (FYM) and poultry compost-on different elite green super rice (GSR) genotypes and were named as NUYT-1, NUYT-2, NUYT-3, NUYT-4, NUYT-5, and NUYT-6. The study was conducted during the 2022 and 2023 rice growing seasons at the Rice Research Program, Crop Sciences Institute (CSI), National Agricultural Research Centre (NARC), Islamabad, one of the mid-latitudes of Pakistan. The key objective was to determine the most effective N management strategy for optimizing plant growth, N content in soil and plants, and overall crop productivity. The results revealed that the combined application of poultry compost and mineral urea significantly enhanced soil and leaf N content (1.36 g kg^{- 1} and 3.06 mg cm^{- 2}, respectively) and plant morphophysiological traits compared to sole urea application. Maximum shoot dry weight (SDW) and root dry weight (RDW) were observed in compost-applied treatment with the values of 77.62 g hill^{- 1} and 8.36 g hill^{- 1}, respectively. The two-year mean data indicated that applying 150 kg N ha⁻¹, with half provided by organic sources (10 tons ha⁻¹ FYM or poultry compost) and the remainder by mineral urea, resulted in the highest N uptake, utilization, and plant productivity. Thus, integrated management of organic carbon sources and inorganic fertilizers may sustain the productivity of rice-based systems more eco-efficiently. Further research is recommended to explore root and shoot morphophysiological, molecular, and biochemical responses under varying N regimes, aiming to develop N-efficient rice varieties through advanced breeding programs.

Keywords: N adsorption and utilization; Organic manures; Rice; Sustainability; plant morphophysiology.

Fig. 1

Effect of partial replacement of synthetic urea with organic fertilizers on shoot dry weight (SDW, g hill^− 1) and leaf N content (%) at maturity on different green super rice (GSR) elite lines (two-year mean 2022 and 2023)

Fig. 2

Effect of partial replacement of synthetic urea with organic fertilizers on root dry weight (RDW, g hill^− 1) and root N content (%) at maturity on different green super rice (GSR) elite lines (two-year mean 2022 and 2023)

Fig. 3

Effect of partial replacement of synthetic urea with organic fertilizers on apparent N recovery efficiency (NRE, %), physiological N use efficiency (NPE, kg kg^− 1), and agronomic N use efficiency (NAE, kg kg^− 1) at maturity on different green super rice (GSR) elite lines (two-year mean 2022 and 2023)

Fig. 4

Effect of partial replacement of synthetic urea with organic fertilizers on dry weight accumulation (mg grain^− 1) of superior and inferior grains of different green super rice (GSR) elite lines (two-year mean 2022 and 2023)

Fig. 5

Effect of partial replacement of synthetic urea with organic fertilizers on grain-filling rate (mg grain^− 1 day^− 1) of superior and inferior grains of different green super rice (GSR) elite lines (two-year mean 2022 and 2023)

Fig. 6

Effect of partial replacement of synthetic urea with organic fertilizers on specific leaf area (SLA, kg m^− 2) of different green super rice (GSR) elite lines (two-year mean 2022 and 2023)

Fig. 7

Effect of partial replacement of synthetic urea with organic fertilizers on leaf area index (LAI) of different green super rice (GSR) elite lines (two-year mean 2022 and 2023)

Fig. 8

Effect of partial replacement of synthetic urea with organic fertilizers on crop growth rate (CGR, g m^− 2 day^− 1) of different green super rice (GSR) elite lines (two-year mean 2022 and 2023)