Liquid organic manures (LOMs) exhibit high variability in dry matter (DM) and nutrient concentrations. Accurate knowledge of these characteristics is essential for farmers to meet plant needs and avoid environmental problems caused by over-fertilization. Near-infrared spectroscopy (NIRS) seems to be a promising tool for the determination of DM and nutrient concentrations directly on farms. In this study, two commercially available NIRS sensors were deployed at 41 farms in northern and southern Germany to assess DM as well as total nitrogen (TN), ammonium nitrogen (AN), phosphorus (P), and potassium (K) under realistic on-farm conditions. A total of 582 samples of cattle and pig slurry as well as biogas digestate were analyzed, and the sensor readings were compared with laboratory values. Both, laboratory measurements and NIRS data revealed high variability in DM and nutrient concentrations across the three LOM types and the two study regions. Both NIRS sensors provided reliable DM data, particularly in pig slurry (R2 > 0.9), while data of TN, AN, P, and K exhibited considerably lower coefficients of determination depending on the substrate, sensor, and region. Furthermore, substantial temporal fluctuations in nutrient concentration were observed within individual storage tanks. Although the NIRS sensors were generally capable of capturing this variability and temporal trends under farm conditions, the quantification of individual nutrients was not sufficiently reliable. Overall, the results show that NIRS has considerable potential for detecting relative changes in nutrient concentrations under farm conditions. However, reliable on-farm application requires improved calibration strategies and better consideration of substrate variability and measurement conditions.
To address excessive nitrogen fertilizer use and inefficient straw management in rain-fed winter wheat production on the Loess Plateau, a three-year split-plot field experiment was conducted. Main plots were assigned to two straw treatments (S0: straw removal; S: straw incorporation), and sub-plots included four nitrogen rates (0, 135, 180, and 225 kg N ha−1). The results showed that straw incorporation combined with moderate nitrogen application markedly improved soil hydrothermal conditions, enhanced soil fertility, and promoted crop performance. Specifically, the optimal treatment—straw incorporation with 180 kg N ha−1 (SN2)—increased soil water content (SWC) in the 0–20 cm layer at harvest by 4.50
High rainfall and weathered soils in the humid tropics create challenges for nutrient management in agriculture. Fertiliser trials in Sumatra have shown variable oil palm responses, possibly due to nutrient losses via runoff and deep drainage. This study quantified losses of K and Mg in both pathways to support nutrient balance calculations and facilitate site-specific fertiliser recommendations. Losses of K and Mg were measured in plots with 23-year-old oil palm on flat and steep slopes at two locations with contrasting average annual rainfall (1668 mm at Bah Lias and 4094 mm at P. Rambong) in North Sumatra. The plots received 118 kg N, 51 kg P, 127 kg K and 31 kg Mg ha−1 a−1 applied in two doses per year. Runoff and deep drainage were measured and analysed for sediment, litter and dissolved K and Mg following rainfall events. As a proportion of rainfall, runoff was 12 and 2
Plastic film mulching (PM) and supplemental irrigation (SI) can enhance crop water productivity (WPc) and crop yield in drylands. However, few studies have reported the differences in water and phosphorus (P) fertilizer use efficiency and crop growth under these practices. In this study, a three-year field trial of winter wheat with four treatments (CK (no P input), recommended practices (FP), PM, and SI (at the stage of wheat regreening)) was carried out in the Loess Plateau of China. Wheat plants and soils were sampled at the elongation and anthesis stages to explore the effects of PM and SI on wheat growth, WPc, and P use efficiency (PUE) and to identify the dominant drivers mediating wheat growth. Results showed that both PM and SI significantly increased wheat yield compared to FP, with average increases of 13.3 and 10.5
Organic fertilizers often contribute to nitrate (NO3−) leaching and impair drinking water quality, because the mineralization of applied organic nitrogen (N) is often asynchronous with crop N uptake. Crop yield, crop N uptake, seepage water and NO3− leaching were investigated in a lysimeter facility (Zurich, Switzerland) under temperate climate conditions during two consecutive four-year organically managed crop rotations. The study compared untreated cattle slurry, anaerobically digested slurry, liquid digestate from a non-agricultural biogas plant and a zero-N fertilization control. The ammonium N (NH4-N) fraction of the organic fertilizers was labeled with 15N tracer to investigate the fate of NH4-N in the plant-soil–water system. Organic fertilization significantly increased crop yields and N uptake, with no differences among organic fertilizers, despite the higher NH4-N proportion of the digestates. Mean annual NO3− leaching was low (12–18 kg N ha−1) and was not increased by organic fertilization, indicating that N inputs were balanced by crop N uptake. Digestates did not differ from untreated cattle slurry in NO3− leaching. Higher modeled ammonia (NH3) emissions of digestates suggest that N losses may occur primarily via NH3 volatilization rather than NO3− leaching. The 15N recovery showed 1
