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Plant–microbe interactions are key to nutrient-use efficiency. Root microbes are influenced by rhizosphere soil and plant cultivars. The impact of cultivar-by-nitrogen (N) interactions on the maize-root microbiome remains unclear, yet it is crucial for understanding N use efficiency in maize. This study evaluated the effects of maize cultivars and N forms, along with their interactions, on the diversity and composition of root bacteria and fungi. Additionally, we examined correlations between soil microbes and root metabolites. The maize cultivar Zhengdan 958 (ZD958) showed a positive response to the mixture of nitrate and ammonium N, resulting in increased in biomass, grain yield, shoot N content, grain N content, and root area. In contrast, the cultivar Denghai605 (DH605) did not exhibit a similar response. The diversity and composition of root bacteria and fungi differed between ZD958 and DH605. The N form primarily affected the community structure of rhizospheric fungi in ZD958 and rhizospheric bacteria in DH605, rather than endophytic microbes. A mixed N supply increased the relative abundance of Basidiomycota, which was positively correlated with ZD958 yield. For DH605, a mixed N treatment enhanced nitrification functions involving Bacteroidetes and Proteobacteria, while it reduced the effects of ammonium N supply. The dominant rhizospheric microbes in DH605 showed a stronger response to changes in root metabolites compared to those in ZD958. A mixed N supply increased the content of palmitoleic acid in ZD958 root exudates, facilitating the recruitment of beneficial rhizospheric microbes, which promotes maize growth. In DH605, a mixed N supply decreased the concentration of sphinganine, which is significantly correlated with Acidobacteria (negatively), Proteobacteria (negatively), Bacteroidetes (positively), and TM7 (positively). Our findings suggest that different maize cultivars respond differently to N forms, causing distinct rhizospheric microbial effects, and that root metabolites send metabolic signals to regulate and recruit key bacterial and fungal communities. [ABSTRACT FROM AUTHOR]

A two-year field experiment was conducted to elucidate the adaptive growth mechanism of maize under strip-till (ST) compared with conventional-till (CT). The biomass accumulation of ST plants was significantly lower than CT until V14 (14th leaf), but restored thereafter with one below-ear-node leaf reduced. At silking, the accumulation of nitrogen (N) was reduced by 8.3–10.7% compared to CT. During post-silking, vegetative-N remobilization was reduced by 20.4%, post-silking N uptake increased by 33.9% in ST compared to CT. Leaf senescence was delayed and more green leaf area at physiological maturity in ST. It is concluded that ST plants have the mechanism of 'Recovery Growth Adaptation' to get the similar yield as in CT plants: (1) facilitating growth rate at around V14 when the soil temperature was greatly improved to stabilize ear growth and grain number; (2) getting to silking the same time as in CT plants, so as to ensure the duration of grain filling; (3) increasing post-silking N uptake to fulfill the demand of grain development and reduce leaf N remobilization, so as to maintain leaf function and increase thousand-grain weight, which compensate for the loss of grain number per ear. [ABSTRACT FROM AUTHOR]

Effective in-season crop nitrogen (N) status diagnosis is important for precision crop N management, and remote sensing using an unmanned aerial vehicle (UAV) is one efficient means of conducting crop N nutrient diagnosis. Here, field experiments were conducted with six N levels and six maize hybrids to determine the nitrogen nutrition index (NNI) and yield, and to diagnose the N status of the hybrids combined with multi-spectral data. The NNI threshold values varied with hybrids and years, ranging from 0.99 to 1.17 in 2018 and 0.60 to 0.71 in 2019. A proper agronomic optimal N rate (AONR) was constructed and confirmed based on the measured NNI and yield. The NNI (R2 = 0.64–0.79) and grain yield (R2 = 0.70–0.73) were predicted well across hybrids using a random forest model with spectral, structural, and textural data (UAV). The AONRs calculated using the predicted NNI and yield were significantly correlated with the measured NNI (R2 = 0.70 and 0.71 in 2018 and 2019, respectively) and yield (R2 = 0.68 and 0.54 in 2018 and 2019, respectively). It is concluded that data fusion can improve in-season N status diagnosis for different maize hybrids compared to using only spectral data. [ABSTRACT FROM AUTHOR]

Plant genotypes shape root‐associated microbiota that affect plant nutrient acquisition and productivity. It is unclear how maize hybrids modify root‐associated microbiota and their functions and relationship with nitrogen use efficiency (NUE) by regulating rhizosphere soil metabolites. Here, two N‐efficient (NE) (ZD958, DMY3) and two N‐inefficient (NIE) maize hybrids (YD9953, LY99) were used to investigate this issue under low N (60 kg N ha−1, LN) and high N (180 kg N ha−1, HN) field conditions. NE hybrids had higher yield than NIE hybrids under LN but not HN. NE and NIE hybrids recruited only distinct root‐associated bacterial microbiota in LN. The bacterial network stability was stronger in NE than NIE hybrids. Compared with NIE hybrids, NE hybrids recruited more bacterial taxa that have been described as plant growth‐promoting rhizobacteria (PGPR), and less related to denitrification and N competition; this resulted in low N2O emission and high rhizosphere NO3−‐N accumulation. NE and NIE hybrids had distinct rhizosphere soil metabolite patterns, and their specific metabolites were closely related to microbiota and specific genera under LN. Our findings reveal the relationships among plant NUE, rhizosphere soil metabolites, root‐associated microbiota, and soil nutrient cycling, and this information is informative for breeding NE crops. [ABSTRACT FROM AUTHOR]

Land application of livestock manure may reduce the use of mineral fertilizers and alleviate the environmental degradation associated with mineral fertilizers application. However, how to optimize utilization of livestock manure value is not well understood and documentation regarding the nitrogen (N) and phosphorus (P) fertilizer replacement values (NFRV and PFRV, respectively) needs further scrutiny. Therefore, three representative livestock manures, i.e., pig, chicken, and cattle manure, were applied at different usages to assess their N and P availability in comparison to reference mineral fertilizers over summer maize growing seasons. The results show that the average NFRVs of pig, chicken, and cattle manures were 41.7–58.4%, 27.5–44.4%, and −3.6–36.1%, respectively, when based on different references (grain yield, total dry matter yield, grain N uptake, total N uptake), at different N application levels. The NFRV increased with the elevated N application rate for cattle manure treatment. In the P trials, livestock manure had a higher PFRV at a low P application level, and the average PFRVs of pig, chicken, and cattle manures were 80.3–164.8%, 77.9–143.7%, and 94.1–168.0%, respectively, at different P application levels. We conclude that livestock manure produced the lowest NFRV and highest PFRV at a low fertilizer application rate; pig manure had the highest N availability; and cattle manure had the highest P availability. [ABSTRACT FROM AUTHOR]

Author(s): Zhenling Cui [1]; Hongyan Zhang [1]; Xinping Chen [1]; Chaochun Zhang [1]; Wenqi Ma [2]; Chengdong Huang [1]; Weifeng Zhang [1]; Guohua Mi [1]; Yuxin Miao [1]; Xiaolin Li [...]