Rhizosphere Processes and Nutrient Management for Improving Nutrient-use Efficiency in Macadamia Production

Abstract

Macadamia (Macadamia spp.) has been widely planted in southern China and has been now developed into an important industry. China has the largest area of macadamia plantation in the world but provides only 3% production of the world. Current farming systems have a fertilizer surplus of about 73 g of nitrogen (N), 103 g of phosphorus (P), and 24 g of potassium (K) per macadamia plant per year in southern China. Optimizing fertilization recommended for macadamia improves production by about 5 kg per plant. Macadamia develops cluster roots (i.e., proteoid roots) in a Pstarvation environment. Overuse of P fertilizers restrains the development of cluster roots as well as rhizosphere processes, thus decreasing the P-use efficiency. Excessive fertilization, especially P fertilization, is one of the major limiting factors in China macadamia production. This study is the first to analyze current management practices and then discuss approaches of improving nutrient management based on the specific root biology of macadamia. For a sustainable macadamia industry, it is imperative to develop appropriate nutrient management by integrating root-zone soil nutrient supply, fertilizer application, and rhizosphere processes.

Long-term continuous mono-cropping of Macadamia integrifolia greatly affects soil physicochemical properties, rhizospheric bacterial diversity, and metabolite contents

“…Glucopyranoside has been observed in petroleum-contaminated soil with a potent ability to reduce total petroleum hydrocarbons (TPHs) ( Wang et al, 2016 ). Our findings suggest using the intercropping system for M. integrifolia cropping to maintain the soil quality and bacterial diversity, as demonstrated previously ( Zhao X. et al, 2019 ). Currently, China is the leading Macadamia planting country; thus, management strategies for sustainable Macadamia orchards are urgently required.…”

“…In southern China, farmers have started Macadamia intercropping with coffee, maize, banana, and tea. Macadamia intercropping with maize decreased the soil temperature and improved fertilizer use and nutrient availability in hot summers ( Zhao X. et al, 2019 ).…”

Global Macadamia Science: Overview of the Special Section

“…Areas of research included propagation, tree physiology, soils and nutrition, pollination biology, pest and disease biology, orchard management, genetics and breeding, developing production areas, and product development. Seven of the presentations are published in this special section Hardner et al, 2019;Howlett et al, 2019;O'Connor et al, 2019;O'Hare et al, 2019;Toft et al, 2019;Zhao et al, 2019).…”

“…Soils and nutrition. J. Shen et al (personal communication) and Zhao et al (2019) report that although the orchard estate in China is expected to become one of the largest globally in the next few years, nutrient management is poor. Chinese farmers apply general fertilizers above or over recommended rates for nitrogen and potassium; however, the application rate of phosphorus is much greater than plant requirements, leading to apparent phosphorus toxicity and deficiency of minor and trace elements.…”

Variability in soil quality among smallholder macadamia farms in Malawi

“…A related study showed that nutritional imbalance promotes oral abortion and contributes to macadamia yield losses (Stephenson et al, 1997). Zhao & Dong (2019) found that excessive application of phosphorus (P) inhibits the development of cluster roots and rhizosphere processes, thereby decreasing the P-use e ciency and inducing iron de ciency. Research undertaken in Malawi has revealed that the majority of the soils lack soil organic matter (SOM) and many of the essential nutrients, including nitrogen (N), potassium (K + ), boron (B), and zinc (Zn) (Matabwa & Rowell, 1997;Njoloma et al, 2016;Gashu et al, 2021).…”