Quality of white cabbage yield and potential risk of ground water nitrogen pollution, as affected by nitrogen fertilisation and irrigation practices

Nitrogen leaching and grey water footprint affected by nitrogen fertilization rate in maize production: a case study of Southwest China

BACKGROUND

Effective nitrogen (N) management measures are required to control environmental problems caused by N fertilizer use in intensive maize production systems. Soil N losses associated with high precipitation and over-fertilization in maize production can cause substantial environmental problems, whereas there is a lack of quantitative data and effective study countermeasures. A 2-year field study was conducted in the subtropical maize production system in Southwest China to quantify N leaching under varying N application rates of 0, 90, 180, 270 and 360 kg N ha^-1  yr^-1 .

RESULTS

The results indicated that N leaching accounted for 16-38% of N fertilizer input. For farmer practice treatment (360 kg N ha^-1  yr^-1 ), N leaching loss was high at 110 kg N ha^-1  yr^-1 and accounted for 31% of the N applied. As an indicator of the ambient water quality pollution, the grey water footprint across all treatments ranged from 376 to 1092 m³ Mg^-1 , with an average of 695 m³ Mg^-1 . Reducing N rate to agronomically optimized treatment (180 kg N ha^-1  yr^-1 ) significantly decreased N leaching by 77%, and maintained high grain yield of 8.1 Mg ha^-1 . The grey water footprint was reduced by 52-63% with N rates from 270 or 360 kg N ha^-1  yr^-1 to 180 kg N ha^-1  yr^-1 .

CONCLUSION

Nitrogen surplus (applied N rate minus N uptake by maize) resulted in higher soil residual nitrate concentration and consequently high N leaching. High precipitation and low soil pH were the main ecological factors leading to high N leaching. © 2021 Society of Chemical Industry.

Nitrogen and Sulphur Fertilisation for Marketable Yields of Cabbage (Brassica oleracea L. var. Capitata), Leaf Nitrate and Glucosinolates and Nitrogen Losses Studied in a Field Experiment in Central Slovenia

A field trial of white cabbage (Brassica oleracea var. Capitata L.) was carried out under the humid temperate climate conditions in Central Slovenia to investigate the effects of calcium ammonium nitrate (0, 180 and 240 kg N ha^-1) and gypsum (0 and 40 kg S ha^-1) fertilisation on yield, yield quality (nitrate, glucosinolate levels and glucosinolate profile) and nitrogen use efficiency. The highest marketable yield, dry matter yield and nitrogen uptake were obtained at the highest nitrogen fertilisation rate when in combination with sulphur. For this treatment, the nitrogen surplus in the soil after harvesting was lower than for the same nitrogen fertilisation without sulphur application. For the combination N₂₄₀S₄₀, the sulphur addition significantly increased nitrogen use efficiency, which resulted in reduced nitrate content in the cabbage heads. The chemical forms of glucosinolates showed that 80-85% were aliphatic glucosinolates with the remainder as the indole group. For the aliphatic glucosinolates, significant interactions between nitrogen and sulphur fertilisations were reflected in increased levels of progoitrin and glucoiberin when sulphur was applied at the lower nitrogen fertilisation rates. For the indole group, the levels of glucobrassicin and the indole group itself decreased at higher nitrogen fertilisation rates, independent of sulphur fertilisation.

Application of a Combined Transmittance/Fluorescence Leaf Clip Sensor for the Nondestructive Determination of Nitrogen Status in White Cabbage Plants

The correct fertilization of vegetable crops is commonly determined on the basis of soil and plant costly destructive analyses, demanding more sustainable non-invasive optical detection. Here, we tested the ability of the combined transmittance/fluorescence leaf clip Dualex device for determining the nitrogen (N) status of cabbage plants. Fully developed leaves from plants grown under different N rates of 0; 100; 200; 300 kg N ha⁻¹ in 2018 and 2019 were measured in the field by the Dualex sensor twice a year in July and October. The chlorophyll (Chl) and nitrogen (nitrogen balance index, NBI) indices and the flavonols (Flav) index of the sensor were positively and negatively correlated to leaf nitrogen, respectively. Merging the two-years data, the NBI versus leaf N correlation was less point dispersed in October than July (R² = 0.76 and 0.64, respectively). NBI was also correlated to cabbage yield, better in July than October. Our results showed that the multiparametric Dualex device can be used as precision agriculture tool for the early prediction of plant N and cabbage yield with economic advantage for the growers and reduced environmental contamination due to nitrate leaching.

Advanced treatment of sewage by membrane bioreactor associate with genetically engineered autotrophic nitrifying bacteria

This study introduced a process of MBR combing with genetically engineered bacteria of expressing nirs and ppk genes (GEB-Nirs/PPK) for advanced treatment of sewage in scenic area. An industrial scale application was staged anaerobic digestion, aerobic digestion. Over more than 150 days of continuous operation, TMP in this system was less than 0.18 bar. With a membrane flux of 6.48 m³/h, TMP remained below 0.2 bar and effluent remained above 70 m³ during continuous operation. Average COD and BOD removals averaged 94.2% and 93.6%, and were obtained with average effluent COD and BOD below 10.4 mg/L and 4.2 mg/L, respectively. The TN and TP removals averaged 98.8% and 94.3%, and never higher than 3.2 mg/L and 0.2 mg/L, respectively, in the processing system. In conclusion, these results indicate that the process of MBR associate with genetically engineered autotrophic nitrifying bacteria is of high-efficiency for advanced treatment of sewage.