Abstract
The replacement of inorganic fertilizer nitrogen by manure is highlighted to have great potential to maintain crop yield while delivering multiple functions, including the improvement of soil quality. However, information on the dynamics of root distributions in response to chemical fertilizers and manure along the soil profile is still lacking. The aim of this study was to investigate the temporal-spatial root distributions of summer maize (Zea mays L.) from 2013 to 2015 under four treatments (unfertilized control (CK), inorganic fertilizer (NPK), manure + 70% NPK (NPKM), and NPKM + straw (NPKMS)). Root efficiency for shoot N accumulation was increased by 89% in the NPKM treatment compared with the NPK treatment at V12 (the emergence of the twelfth leaf) of 2014. Root growth at 40–60 cm was consistently stimulated after manure and/or straw additions, especially at V12 and R3 (the milk stage) across three years. Root length density (RLD) in the diameter <0.2 mm at 0–20 cm was significantly positively correlated with soil water content and negatively with soil mineral N contents in 2015. The RLD in the diameter >0.4 mm at 20–60 cm, and RLD <0.2 mm, was positively correlated with shoot N uptake in 2015. The root length density was insensitive in response to fertilization treatments, but the variations in RLD along the soil profile in response to fertilization implies that there is a great potential to manipulate N supply levels and rooting depths to increase nutrient use efficiency. The importance of incorporating a manure application together with straw to increase soil fertility in the North China Plain (NCP) needs further studies.
Highlights
Crop yields and quality depend upon substantial nitrogen (N) inputs [1]
Compared with CK, fertilization treatments significantly increased the grain per spike, and no significant difference was observed among the fertilized treatments
The thousand-kernel weight (TKW) in the compost was lower than that in the NPK treatment, but no significant difference was observed between the NPKM and NPK + 30% compost + wheat straw (NPKMS) treatments (Table 1)
Summary
Crop yields and quality depend upon substantial nitrogen (N) inputs [1]. Modern agriculture depends on high external inputs of chemical N fertilizers to achieve high crop productivity, whereby excessive N leads to low nutrient use efficiency and is recognized to be a major cause of environmental problems, including N leaching and soil acidification [2,3]. The overuse of chemical fertilizers in excess of crop nutrient demand does not increase grain yield. Mining the biological potential of crop roots has been proposed to be one of the possible solutions to increase N efficiency [4,5], as roots are closely associated with soil resource acquisition and are central for achieving a high crop yield. Roots play important roles in the anchorage of plants, the synthesis of growth regulators, and storage
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