Accurate assessment of crop nitrogen nutrition status is essential for precision fertilization and sustainable agricultural development. This study aimed to develop rapid and non-destructive diagnostic models to predict aboveground plant nitrogen concentration (PNC), leaf area index (LAI) and nitrogen nutrition index (NNI) of sorghum by means of unmanned aerial vehicle (UAV)-based hyperspectral remote sensing. Further the built models were validated across different cultivars and regions. Field experiments were conducted in 2024 at two sites (Shanyin and Yuci) in Shanxi Province. At Shanyin, the field experiment comprised six nitrogen application rates (0, 30, 75, 150, 225, and 300 kg/hm2) and three sorghum varieties (Jinzao 5564, Jinzao 5577, and Jinza 22). At the Yuci site, long-term fertilization experiments, using Jinza 22, included five treatments: no fertilization (CK), nitrogen omission (PK), phosphorus omission (NK), potassium omission (NP), and complete NPK fertilization (NPK), which were initiated in 2011. During sorghum vegetative growth period, plants samples were collected at 41, 50, 63, and 72 days after emergence at Shanyin, and at 28, 37, and 59 days after emergence at Yuci. Simultaneously, a drone equipped with a hyperspectral sensor was utilized to acquire remote sensing data over the study area. Aboveground PNC and LAI were determined immediately after sampling. NNI was calculated based on PNC and critical N concentration (Nc), which was estimated using a critical nitrogen dilution curve derived from LAI established from previous research. Competitive adaptive reweighted sampling (CARS), uninformative variable elimination (UVE) and successive projections algorithm (SPA) were applied to raw spectral reflectance (R) and first-derivative reflectance spectra (FDR) to identify characteristic spectral bands. Partial least squares regression (PLSR) models were developed based on data from Jinzao 5564 and Jinzao 5577. Jinza 22 was used for cultivar validation, and Yuci experiment served for regional validation. Model performance was evaluated using the coefficient of determination (R2) and root mean square error (RMSE). Results showed that nitrogen application significantly influenced aboveground PNC, LAI, and NNI (P < 0.05). PNC gradually declined during crop development, whereas LAI increased over time. N application significantly promoted NNI, which reached 1 at an application rate of 150 kg/hm2. In the long-term experiment conducted at Yuci site, NNI values reached 1 when nitrogen was applied (e. g. NK, NP and NPK treatments); whereas it ranged from 0.46 to 0.67 for both the CK and PK treatments. Sensitive spectral bands were selected from R and FDR to predict PNC, LAI, and NNI using CARS, UVE and SPA, respectively. Regardless of whether R or FDR were used, the feature bands sensitive to PNC, LAI and NNI were mainly concentrated in the range from red to near-infrared. However, in terms of the same predicted indicator, the sensitive feature bands were variable brought from feature selection algorithm. The PLSR model based on raw spectral reflectance combined with CARS-selected bands achieved the best performance for predicting PNC (R2 = 0.907, RMSE = 0.163%) and LAI (R2 = 0.940, RMSE = 0.480) on the test set. In cross-cultivar validation, the R2 of R-CARS model for PNC and LAI were 0.883 and 0.878, respectively. For cross-regional validation, meanwhile the corresponding R2 values were 0.643 and 0.911. The PLSR model using raw spectral reflectance combined with UVE-selected bands provided the highest accuracy for NNI prediction, with an R2 of 0.754 and RMSE of 0.086. The R2 values for cultivar and regional validation were 0.666 and 0.529, respectively. Although cross-regional prediction accuracy for PNC and NNI were lower than that of the test set, the spatiotemporal distribution patterns of the predicted PNC, LAI, and NNI remained consistent with nitrogen application gradients and the dynamics of nitrogen nutrition across growth stages. In conclusion, the developed models effectively captured variations in nitrogen supply adequacy, providing reliable technical support for nitrogen status diagnosis and precision nitrogen management in sorghum cultivation.
- Article type
- Year
- Co-author
This study was conducted to clarify effects of different row spacings and planting densities on the development, yield, grain quality and NPK (nitrogen, phosphorus and potassium) accumulation of grain-feeding sorghum, and to identify the optimal cultivation mode in agro-pastoral ecozone of Shanxi, so as to provide the theoretical basis for the grain-feeding sorghum cultivation.
A new grain-feeding sorghum variety Liaoxialiang No. 1 was selected for this study. Field experiments were conducted during 2018 and 2019. Three row spacings were set, i.e. 30, 50, and 60 cm, respectively. And there were four planting densities (13.5×104, 16.5×104, 19.5×104 and 22.5×104 plants/hm2) at each row spacing. The plant height and biomass at heading stage, grain yield, NPK accumulation at harvest and grain quality in different row spacings and planting densities were analyzed.
There were significantly effects of row spacing, planting density and their interaction on the grain-feeding sorghum growth, nutrient accumulation, grain yield and quality. As plant density increased, the plant height, biomass and NPK accumulation at heading stage were increased. However, the biomass produced after heading, biomass and NPK accumulation at harvest, along with yield, increased first and then decreased with the increase of density under row spacing with 50 and 60 cm; Actually, the grain yield of feeding sorghum was positively correlated with biomass and N accumulation at harvest and the biomass produced after heading. The average grain yield, N and P accumulation and biomass after heading in row spacing of 50 cm were higher than those of 60 and 30 cm. Among the 12 treatments, the treatment with row spacing of 50 cm, planting density of 16.5×104 plants/hm2 had improved biomass and N accumulation at harvest, which were increased by 3.6%-12.8% and 3.6%-18.6%, respectively, relative to the average value of the total 12 treatments. The grain yield with row spacing of 50 cm and planting density of 16.5×104 plants/hm2 was the highest among all treatments, and they were 10 814 kg·hm-2 in 2018 and 12 434 kg·hm-2 in 2019, respectively. Starch and protein content of grain decreased with planting density increasing, but the influence of row spacing variation on them were less. Grain tannin content was significantly increased with planting density adding, while the row spacing increase also promoted tannin content. The influence of row spacing and planting density on tannin content was obvious, compared with those on starch and protein. Those treatments with row spacing of 50 cm and density of 16.5×104 plants/hm2 had similar tannin content with the average value of different treatments.
Both N accumulation and biomass production after heading were important for high grain yield of feeding sorghum. The appropriate plant spacing under different row spacings could improve feeding sorghum grain yield, but affect grain quality, especially the tannin content. Row spacing of 50 cm and density of 16.5×104 plants/hm2 was recommended in agro-pastoral ecozone in Shanxi (with variety of Liaoxialiang No.1) in terms of grain yield and quality of feeding sorghum.
To provide the theoretical basis for rational nitrogen (N) application and promoting high yield and high quality of foxtail millet (Setaria italica (L.) Beauv.), this study aimed to clarify the effects of different N application rates on plant N utilization characteristics, grain yield and grain quality of foxtail millet.
To investigate the effects of different N application levels on plant N accumulation, transfer and utilization characteristics, grain yield and its components, grain micronutrients content and pasting properties, a 2-year field experiment (2020-2021) was performed with different N fertilization application at four levels (0, 75, 120, and 150 kg·hm-2, represented as N0, N75, N120, and N150, respectively) in the Qinxian County of Shanxi Province, located in the spring sowing region of China.
Compared with N0, N application increased panicle number per unit area at harvest, grain number per panicle and plant productivity of foxtail millet. N application also significantly enhanced N translocation and promoted the distribution of both dry matter and N in grains. As a consequence, an enhanced grain yield was obtained when subjected to N application. Further, among all treatments, the highest values of panicle number per unit area at harvest, grain number per panicle, both grain yield and biomass, harvest index, total N accumulation and N translocation efficiency were obtained when 75 kg·hm-2 was supplied; compared with the values produced by N0, the increased rate reached 7.5%, 23.3%, 31.0%, 21.2%, 8.6%, 40.3% and 9.2% by N75, respectively. Compared with N0 treatment, the content of Fe, Zn, Ca, Mg and Se in foxtail millet grains under N75 treatment were increased by 37.3%, 43.6%, 56.0%, 30.5% and 16.9% at most, respectively. Excessive N application (N 150) decreased grain number, harvest index and N translocation efficiency compared with N75 treatment. More than 75 kg·hm-2 application resulted in diminished N translocation efficiency, by 23.1% and 28.1%, in 2020 and 2021, respectively. The content of amylopectin and starch yield were also limited by excessive N. Over-use N fertilizer also significantly decreased final viscosity, setback and trough viscosity. Pearson correlation coefficients demonstrated a strong positive relationship between plant N accumulation and the content of Fe, Zn, Ca, Mg and Se in foxtail millet grains, and a significant negative relationship between plant N accumulation and the content of amylopectin, final viscosity and trough viscosity in foxtail millet grains.
The N application at 75-120 kg·hm-2 could promoted the allocation of dry matter and N in grain, which was relative to the enhanced N transfer from vegetative organs to grains. Also the reasonable pasting properties and biofortification of beneficial trace elements of Fe, Zn, Ca, Mg and Se was produced by such N dose in this study area.
The effects of long-term different fertilizations and deep plough on grain yield, potassium utilization, potassium forms in soil profile and non-exchange potassium release in maize-sorghum rotation system was evaluated to provide the theoretical basis for potassium nutrient management.
The experiment was conducted in Jinzhong city of Shanxi Province from 2011 to 2022. There were 6 treatments: no fertilizer (CK), NP, NPK, straw return and manure (MS), NPK with MS (NPKMS) and NPKMS with deep plough for 30 cm (NPKMSD). The influences of different treatments on grain yield, potassium uptake, potassium apparent utilization efficiency (KUE), potassium agronomy utilization efficiency (KAUE) and kinetics of non-exchange release were investigated.
Compared with NP and NPK treatments, the accumulative grain yield was increased 6%-8% under MS, NPKMS and NPKMSD, whereas potassium uptake was promoted 22%-43%. Moreover, the values of PAUE produced by NPKMS and NPKMSD were only half under NPK and MS treatments. The available K content of 0-20 cm soil layer under MS, NPKMS and NPKMSD treatments were 2.2 to 2.8 times higher than those under CK, NP and NPK treatments. Meanwhile, the slow available K was increased 8%-10%. The deep plough enhanced available K content of 20-40 cm soil layer. The K uptake aboveground was more related to available K content of both 0-20 cm and 20-40 cm soil layer and slow available K content of 20-40 cm soil layer. When the soil non-exchangeable K was extracted by CaCl2, the accumulative amount of K released under NPK, MS, NPKMS, and NPKMSD were 1.04, 1.77, 1.99, and 1.81 times than that under NP treatment, respectively, while these values were 1.05, 1.41, 1.85, and 1.63 times under NP treatment when soil non-exchangeable K was extracted by citric acid.
Taken together, straw return and manure could activate soil potassium. Thus soil available K content, slow available K content, KUE and KAUE were improved relative to NPK treatments when total potassium input was comparative for 12-years. NPK with MS treatments could induce potassium luxury absorption and resulted in low values of KUE and KAUE. Deep plough could increase subsoil available K content, but its impact on accumulative grain yield was not noticed. Straw return and manure increased cumulative non-exchangeable potassium release amount and release rates. Therefore long-term combination of straw return and appropriate amount manure could substitute chemical potassium fertilizer.
京公网安备11010802044758号