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Root and rhizosphere research has been conducted for many decades, but the underlying strategy of root/rhizosphere processes and management in intensive cropping systems remain largely to be determined. Improved grain production to meet the food demand of an increasing population has been highly dependent on chemical fertilizer input based on the traditionally assumed notion of 'high input, high output', which results in overuse of fertilizers but ignores the biological potential of roots or rhizosphere for efficient mobilization and acquisition of soil nutrients. Root exploration in soil nutrient resources and root-induced rhizosphere processes plays an important role in controlling nutrient transformation, efficient nutrient acquisition and use, and thus crop productivity. The efficiency of root/rhizosphere in terms of improved nutrient mobilization, acquisition, and use can be fully exploited by: (1) manipulating root growth (i.e. root development and size, root system architecture, and distribution); (2) regulating rhizosphere processes (i.e. rhizosphere acidification, organic anion and acid phosphatase exudation, localized application of nutrients, rhizosphere interactions, and use of efficient crop genotypes); and (3) optimizing root zone management to synchronize root growth and soil nutrient supply with demand of nutrients in cropping systems. Experiments have shown that root/rhizosphere management is an effective approach to increase both nutrient use efficiency and crop productivity for sustainable crop production. The objectives of this paper are to summarize the principles of root/rhizosphere management and provide an overview of some successful case studies on how to exploit the biological potential of root system and rhizosphere processes to improve crop productivity and nutrient use efficiency.

Nitrogen (N) over-application is a serious problem in intensive agricultural production areas with consequent large N losses and environmental pollution. In contrast to N, potassium (K) application has been neglected in many developing countries and this has resulted in soil K depletion in agricultural ecosystems and prevented increases in crop yields. Nitrogenpotassium interaction is currently a topic of interest in many studies and the focus of this review is K nutrition under varied N regimes. Nitrogen form and application rate and time influence soil K fixation and release, as well as K uptake, transport, cycling and reutilization within crops. High yielding quality crops can be obtained by optimal N: K nutritional ratios. High rates of applications of N and K do not necessarily lead to increased yield increments and may even reduce yield. Yield response to K uptake depends on N nutritional status and the interaction is usually positive when NO 3 − -N is supplied. Antagonism between NH 4 + and K + in uptake was mostly attributed to simple competitive effects in the past while evidence showing mixednoncompetitive interactions existed. Two components of membrane transport systems for K uptake by plants are a high-affinity K + transport system which is inhibited by NH 4 + and a low-affinity K + transport system which is relatively NH 4 + insensitive. Potassium is highly mobile within plants but its flow and partitioning can change depending on the forms of N supply. NH 4 + nutrition in comparison to NO 3 − -supply results in more K translocation to leaves. A better understanding of the mechanism of N-K interaction can be a useful guide to best nutrient management in agricultural practice in order to achieve high yields with high nutrient use efficiency.

Two‐branched pea plants (Pisum sativum L. cv. Lisa ZS) with different dominance degrees, obtained by removing the epicotyl shortly after germination, were used to study the interaction between the polar transport of indoleacetic acid (IAA) in both branches of the plants and its relationship to correlative dominance. The dominant shoot had higher transport capacity for C‐IAA applied to the cut stump of one side of the Y‐form explant was used, the stronger the H‐IAA transport was inhibited and the more the transported IAA was conjugated above the junction on the other side. The results of these experiments support the autoinhibition hypothesis at junctions. The relationship between elongation growth and IAA export/transport in the two‐branch pea plants is considered.

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