Water shortage caused by long-term drought is one of the most serious abiotic stress factors in maize. Different drought conditions lead to differences in growth, development, and metabolism of maize. In previous studies, proteomics and genomics methods have been widely used to explain the response mechanism of maize to long-term drought, but there are only a few articles related to metabolomics. In this study, we used transcriptome and metabolomics analysis to characterize the differential effects of drought stress imposed at seedling or flowering stages on maize. Through the association analysis of genes and metabolites, we found that maize leaves had 61 and 54 enriched pathways under seedling drought and flowering drought, respectively, of which 13 and 11 were significant key pathways, mostly related to the biosynthesis of flavonoids and phenylpropanes, glutathione metabolism and purine metabolism. Interestingly, we found that the α-linolenic acid metabolic pathway differed significantly between the two treatments, and a total of 10 differentially expressed genes and five differentially abundant metabolites have been identified in this pathway. Some differential accumulation of metabolites (DAMs) was related to synthesis of jasmonic acid, which may be one of the key pathways underpinning maize response to different types of long-term drought. In general, metabolomics provides a new method for the study of water stress in maize and lays a theoretical foundation for drought-resistant cultivation of silage maize.

Root lodging is known to reduce the yield and quality of maize, which will be more serious driven by the changes in agriculture such as the higher planting density and the more extreme precipitation events. Here we describe a new cultivation method to reduce the root lodging of maize. We designed two planting layouts: twin plants (TP) and single plant (SP) in a hole with the same density. The vertical root-pulling resistance, angle and rate of natural root lodging, root and shoot morphology related to root lodging and maize yield were compared between two planting layouts. TP planting significantly increased the vertical root-pulling resistance and angle of natural root lodging. This can be partly attributed to the gripping force between the staggered crown roots of the two adjacent plants. Moreover, the TP planting could increase root-lodging resistance by increasing the root angle (acute angle between the stem direction and root) and stem diameter. Additionally, TP planting did not reduce the maize yield and biomass. Consequently, our study demonstrated that the twin plants in a hole are effective to decrease the root lodging of maize in southwest of China. This technique is simple, inexpensive, safe, stable, and has broader potential for increasing maize yield and quality. Twin plants layout in wide-narrow rows significantly increased the vertical root-pulling resistance of maize, which mainly attributed to the gripping force between the staggered crown roots of the two adjacent plants.

Prolonged drought stress caused by global warming poses a tremendous challenge to silage production of maize. Drought during maize growth and development resulted in altered micro-environment for silage fermentation. How fermentation of silage maize responds to moisture scales remains uncharted territory. In this research, Maize water control trials were conducted and the silage quality and microbial community of drought-affected maize were determined. The results showed that drought stress significantly reduced the dry matter but increased root-to-shoot ratio, soluble sugar and malonaldehyde content in maize. Before fermentation, the crude protein, crude ash and acid detergent fiber contents were significantly increased but the ether extract content was decreased under drought. The crude protein and acid detergent fiber were significantly decreased in the drought affected group after fermentation. Furthermore, water stress at maize maturity stage greatly reduced the number of total bacteria in silage fermentation but increased the proportion of the lactobacillus and lactic acid content of silage. Drought stress alters the microbial ecosystem of the fermentation process and reconstitutes the diversity of the bacterial community and its metabolites. This study provides a theoretical basis for the study of changes in silage fermentation as affected by abiotic stresses.

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Crop-livestock systems are critical for global agricultural sustainability. Here we show for the first time a new crop-livestock system: farming Muscovy ducks in maize fields (FD). To test whether FD is a practicable crop-livestock system, we conducted a 3-year field experiment to explore the growth and weight performance of Muscovy ducks in FD and to compare the FD with conventional maize planting (CMP) and raising ducks indoors (RDI) regarding crop growth and yield, weed biomass and density, feed conversion ratio, and economic benefits. We found that Muscovy ducks could adapt and thrive in maize fields with grain supplementation. The average weight per duck in FD at the harvest stage of maize was 2.24-3.82 kg, which met the local market standard and was higher than in RDI with a lower feed conversion ratio. When compared to CMP, FD did not significantly reduce the maize production in terms of yield or biomass, although the ducks fed on or damaged an average of four maize leaves. Importantly, FD significantly reduced the weed biomass and density. In addition, the net present value (NPV) of FD was $ 6690.47 per ha or $ 10.993 per duck, which was three times and 22.8% greater than those of CMP and RDI, respectively. These results indicated that FD, as a new crop-livestock system on dry land at the field scale, can promote sustainable agricultural production and act as a potential crop-livestock system due to the large global maize area.