Effects of Combined Potassium and Organic Fertilizer Application on Newhall Navel Orange Nutrient Uptake, Yield, and Quality

Mingxia Wen,Yongqiang Zheng,Shilai Yi,Ji Zhang

doi:10.3390/agronomy11101990

Mingxia Wen, Yongqiang Zheng + Show 2 more

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https://doi.org/10.3390/agronomy11101990

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Abstract

In this study, we investigated the effects of the combined application of different doses of potassium and organic fertilizers on the nutrient uptake, yield, and quality of Newhall navel oranges (Citrus sinensis Osb. cv.). The citrus trees were treated with potassium fertilizer alone or with one of three combinations of organic and potassium fertilizers. Spring shoots, autumn shoots, and fruit were collected when they reached maturity, and the relevant indexes were determined by conventional methods. The soil carbon flux was measured 15, 35, 65, and 95 days after fertilizer application by a soil gas flux measuring instrument. The results showed that the dry weights of leaves and twigs of the spring shoots were 43.1% and 99.8% higher in the OM15+K05-treated (15 kg organic manure and 1.05 kg potassium sulfate per plant) than in the OM0+K25-treated (1.25 kg potassium sulfate per plant) plants, respectively. Combined potassium and organic fertilizer application helped the shoots and fruits to absorb more mineral nutrients. As a result, the fruit yield increased, fruit surface color improved, and skin thickness became thinner. The internal quality of the fruit was also improved by the combination of different potassium fertilizers and organic fertilizers. The fruit quality was optimal for the OM10+K15-treated plants. The recommended doses of organic and potassium sulfate fertilizers for Newhall navel orange orchards with purple paddy soil in southwestern China are 5–10 kg/plant and 1.15–1.20 kg/plant, respectively.

Highlights

Citrus is an economically important crop in China
Our study found that the dry matter accumulation in the spring shoots was highest in the OM15+K05-treated trees, indicating that combined potassium and organic fertilizer application helped to change the unfavorable growth conditions and promote the growth of the citrus plants
Combined potassium and organic fertilizer application can quickly meet the nu-trient requirements of Newhall navel orange trees at different growth stages, which promotes the accumulation of nutrients in the autumn shoots

Summary

Introduction

Citrus is an economically important crop in China. China’s citrus yield reached 41.3 million tons in 2018, accounting for 16.1% of China’s total fruit yield; citrus production still suffers from low yields per unit area, varying fruit quality, and low yield of high-quality fruits. There is a pressing need to develop effective approaches to improve citrus yield and quality. By adjusting plant water requirements through influencing the transpiration process [2], K plays a key role in the transport of photosynthates, the regulation of stomatal physiological mechanisms, the synthesis of carbohydrates [3], and is directly related to the regulation of the cell osmotic potential to minimize stress responses [4]. Potassium plays a vital role in fruit development, and in enhancing fruit size, color, and flavor [6]. With its long growth cycle, is a nutrient-demanding fruit tree, and is highly responsive to applied nutrients in the form of fertilizers. The growth of citrus fruit removes an abundance of K, more than any other nutrient [7]; a deficiency of K severely affects the fruit quality, as well as the final yield, of citrus. Excessive K application decreases the economic return and had no positive effects on fruit yield [9,10]

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