The impact of NPK fertilizer on growth and nutrient accumulation in juniper (Juniperus procera) trees grown on fire-damaged and intact soils

The impact of chemical and hormonal treatments to improve seed germination and seedling growth of Juniperus procera Hochst. ex Endi

Purpose

Juniper (Juniperus procera) is a common forest tree species in Saudi Arabia. The decline in many populations of J. procera in Saudi Arabia is mainly due to seed dormancy and loss of natural regeneration. This study assessed the effects of chemical and hormonal treatments on seed germination and seedling growth in juniper plants.

Methods

The seeds were subjected to either chemical scarification with 90% sulfuric acid and 20% acetic acid for 6 min or hormonal treatment by seed soaking in two concentrations (50 and 100 ppm) of three growth regulators, namely, indole acetic acid (IAA), gibberellins (GA3), and kinetin, for 72 h. A control group without any seed treatment was also prepared. The experiments were performed in an incubator maintained at room temperature and under a light and dark period of 12 h for 6 w. The germinated seeds for each treatment were counted and removed from the dishes. The selected germinated seeds from different treatments were planted in a greenhouse and irrigated with tap water for another 6 weeks. The hormone-treated seedlings were sprayed with their corresponding hormone concentrations 1 w after planting.

Results

The highest percentage of seed germination was significantly recorded after seed soaking in 50 ppm GA3, whereas treatment with IAA (100 ppm) resulted in the best seedling growth. Seedlings treated with the three phytohormones showed a significant increase in photosynthetic pigments, total soluble sugars, proteins, percentage of oil, IAA, GA3, and kinetin contents of juniper seedlings compared with the control value, whereas abscisic acid content was decreased compared with chemical treatments.

Conclusion

The investigated different treatments had an effective role in breaking seed dormancy and improving seedling growth of J. procera, which is facing a notable decline in its population worldwide. Moreover, such an effect was more pronounced in the three phytohormones that succeeded in breaking dormancy and growth of the Juniperus plant than in the other treatments.

Correction: The impact of NPK fertilizer on growth and nutrient accumulation in juniper (Juniperus procera) trees grown on fire-damaged and intact soils

[This corrects the article DOI: 10.1371/journal.pone.0262685.].

Suitable split nitrogen application increases grain yield and photosynthetic capacity in drip-irrigated winter wheat (Triticum aestivum L.) under different water regimes in the North China Plain

Chemical fertilizer overuse is a major environmental threat, critically polluting soil and water resources. An optimization of nitrogen (N) fertilizer application in winter wheat (Triticum aestivum L.) in association with various irrigation scheduling is a potential approach in this regard. A 2-year field experiment was carried out to assess the growth, yield and photosynthetic capacity of drip-irrigated winter wheat subjected to various split applications of urea (240 kg ha^-1, 46% N). The eight treatments were, two irrigation scheduling and six N application modes in which, one slow-release fertilizer (SRF). Irrigation scheduling was based on the difference between actual crop evapotranspiration and precipitation (ETa-P). The two irrigation scheduling were I₄₅ (Irrigation scheduling when ETa-P reaches 45 mm) and I₃₀ (Irrigation scheduling when ETa-P reaches 30 mm). The six N levels were N_0-100 (100% from jointing to booting), N_25-75 (25% during sowing and 75% from jointing to booting), N_50-50 (50% during sowing and 50% from jointing to booting), N_75-25 (75% during sowing and 25% from jointing to booting), N_100-0 (100% during sowing), and SRF₁₀₀ (240 _kg ha^-1, 43% N during sowing). N top-dressing application significantly (P<0.05) influenced wheat growth, aboveground biomass (ABM), grain yield (GY) and its components, photosynthetic and chlorophyll parameters, and plant nutrient content. According to the averages of the two winter wheat-growing seasons, the I₄₅N_50-50 and I₄₅SRF₁₀₀ treatments, respectively had the highest GY (9.83 and 9.5 t ha^-1), ABM (19.91 and 19.79 t ha^-1), net photosynthetic rate (35.92 and 34.59 µmol m^-2s^-1), stomatal conductance (1.387 and 1.223 mol m^-2s^-1), SPAD (69.33 and 64.03), and chlorophyll fluorescence F_V/F_M (8.901 and 8.922). The present study provided convincing confirmation that N applied equally in splits at basal-top-dressing rates could be a desirable N application mode under drip irrigation system and could economically compete with the costly SRF for winter wheat fertilization. The I₄₅N_50-50 treatment offers to farmers an option to sustain wheat production in the NCP.