No abstract

Maize is the staple food of China, produced on 33.6% of the total arable land. In this context, an effective strategy to enhance maize yield is essential to meet the demand without expanding the cultivation areas. Maize yield can be increased by two key measures: plant-row space optimization and nutrient management. However, in traditional maize cultivation practices, fertilizer utilization by plants is inefficient. We therefore performed a manipulative experiment over two years (2018–2019), applying four treatments: (I) linear planting with nitrogen fertilization at 10 cm depth (CK), (II) linear planting with nitrogen fertilization at 20 cm depth (LD20), (III) zigzag planting with nitrogen fertilization at 10 cm depth (ZD10), and (IV) zigzag planting with nitrogen fertilization at 20 cm depth (ZD20). The aim of this study was to examine the influence of deep nitrogen fertilization and zigzag planting alone and in combination with root distribution, soil properties, canopy structures, and maize yield. Our results showed that all improved maize cultivating strategies (LD20, ZD10, and ZD20) increased the root length density up to 10–30 cm depth of soil layers compared to CK. Similarly, deep nitrogen fertilization increased the photosynthesis rate and leaf area duration after the silking stage. The leaf orientation value of the middle and upper canopies increased in zigzag planting compared to linear planting. It also increased the dry matter accumulation of medium leaves, leaf area duration, and dry matter accumulation after the silking stage. The maize yield was highly increased in ZD20 followed by ZD10, LD20, and the least by CK (traditional cultivating practices) in both years. Our study suggests that zigzag planting provides a higher yield than linear planting. Additionally, deep nitrogen fertilization in zigzag planting significantly increases the population resource utilization rate and yield by optimizing the root–canopy structures. Row spacing and nitrogen fertilization were found to be essential to enhance crop yield by influencing root growth and canopy efficiency.

Using organic fertilizer and maize straw as friendly amendment measures is effective for altering soil nitrogen (N) cycling in farmlands. However, the synthetical effects of organic fertilizer combined with straw returning on soil quality remain unknown, especially in response to soil nitrification and denitrification microorganisms. We set up an experiment in brunisolic soil from Northeast China, mainly including four treatments: CK (no addition without traditional chemical fertilizer), O (organic fertilizer application), S (straw returning), and OS (organic fertilizer combined with straw returning). The soil nitrification and denitrification microorganisms were further investigated using high-throughput sequencing. Our results show that, compared to CK, the soil water content, field capacity, macroaggregates with a diameter > 0.25 mm, mean weight diameter, total carbon, total nitrogen, ammonium, nitrate, microbial biomass carbon, and microbial biomass nitrogen were significantly improved, and penetration resistance was reduced in a 0–20 cm soil layer under O, S, and OS treatments. Moreover, OS treatment effectively increased the available potassium and available phosphorus content and decreased the three-phase R-value. The application of organic fertilizer and straw effectively optimized the soil structure, especially the OS treatment. Compared to CK, O, S, and OS treatments had a higher abundance of ammonia-oxidizing archaea (AOA) and further enhanced the alpha diversity and lower abundance of ammonia-oxidizing bacteria (AOB) and nirK-, nirS-, and nosZ-type denitrifying microbes. AOA and nirK were the key drivers of the ammonia oxidation process and nitrite reduction process, respectively. Meanwhile, the application of organic fertilizer and straw regulated the relative abundance of Nitrososphaeria (AOA), Gammaproteobacteria (nirK and nirS), Alphaproteobacteria (nirK), and Betaproteobacteria (nirS) in the soil. Organic fertilizer and straw returning regulated the soil structure by enhancing the abundance of Alphaproteobacteria, Betaproteobacteria, and Gammaproteobacteria in the nitrifying and denitrifying microorganism communities. Taken together, OS treatment was a suitable straw-returning practice for optimizing the nutrient balance of the farmland ecosystem in Northeast China. However, this study did not determine how to reduce traditional nitrogen fertilizer applications under organic fertilizer application and straw returning; therefore, we aim to carry out related research in future works.