Growth and yield of maize in response to reduced fertilizer application and its impacts on population dynamics and community biodiversity of insects and soil microbes

Abstract

In the North China Plain, farmers are using excessive amounts of fertilizer for the production of high-yield crop yield, which indirectly causes pollution in agricultural production. To investigate an optimal rate of fertilizer application for summer maize, the fertilizer reduction experiments with 600 kg/ha NPK (N: P₂O₅: K₂O = 28: 8: 10) as normal fertilizer application (NFA), (i.e., 100F), were conducted successively during 2020 and 2021 to study the effects of reduced fertilizer rates, including 90% (540 kg/ha; i.e., 90F), 80% (480 kg/ha; i.e., 80F), 62.5% (375 kg/ha; i.e., 62.5F) and 50% (300 kg/ha; i.e., 50F) of NFA, on the plant growth of maize, the dynamics of key population abundances and community diversity of insects, and the composition and diversity of microbial community and finally to find out the N-metabolic enzymes' activity in soil. Our findings revealed that the fertilizer reduction rates by 10% - 20% compared to the current 100% NFA, and it has not significantly affected the plant growth of maize, not only plant growth indexes but also foliar contents of nutrients, secondary metabolites, and N-metabolic enzymes' activity. Further, there was no significant alteration of the key population dynamics of the Asian corn borer (Ostrinia furnacalis) and the community diversity of insects on maize plants. It is interesting to note that the level of N-metabolic enzymes' activity and microbial community diversity in soil were also not affected. While the fertilizer reduction rate by 50% unequivocally reduced field corn yield compared to 100% NFA, significantly decreased the yield by 17.10%. The optimal fertilizer application was calculated as 547 kg/ha (i.e., 91.17% NFA) based on the simulation analysis of maize yields among the five fertilizer application treatments, and the fertilizer application reduced down to 486 kg/ha (i.e., 81.00% NFA) with a significant reduction of maize yield. These results indicated that reduced the fertilizer application by 8.83% - 19.00% is safe and feasible to mitigate pollution and promote sustainable production of maize crops in the region.

Keywords: biomass and yield; fertilizer reduction; insects; maize; soil microbes.

Figure 1

Field layout model of the fertilizer application treatments to affect the plant growth and yield production of maize, and dynamics of key populations and community diversity of insects. (100F - normal fertilizer application (NFA) of 600 kg NPK (N: P₂O₅: K₂O = 28: 8: 10) per hectare (ha.); 90F, 80F, 62.5F and 50F - the four fertilizer reduction gradients with 90% (540kg/ha), 80% (480kg/ha), 62.5% (375kg/ha) and 50% (300kg/ha) of NFA, respectively; The row spacing and plant distance of corn was 0.80 m and 0.20 m respectively. The same in the following figures).

Figure 2

Agronomic traits (A–D) of plant growth, foliar nutrition (E–G) and nitrogen metabolic enzyme activity (H–J) of maize plants during the dough stage under different fertilizer application levels. (Vertical bars denote the standard error of the mean. Different uppercase and lowercase letters represent significant differences among different fertilizer application treatments in 2020 and 2021 respectively, by the LSD test at P< 0.05. The same as in the following figures).

Figure 3

Secondary metabolites (A–C) and plant hormones (D–F) in maize leaves during the dough stage under different fertilizer application treatments. (Vertical bars denote the standard error of the mean. Different uppercase and lowercase letters represent significant differences among different fertilizer application treatments in 2020 and 2021 respectively, by the LSD test at P< 0.05. The same as in the following figures).

Figure 4

Grain yield (A, B) and nutrients (C–H) of maize with different fertilizer application treatments in 2020 and 2021; and Fitting function (I) based on the relationship between maize yield and fertilizer application (300, 375, 480, 540 and 600 kg/ha) of NPK (N: P₂O₅: K₂O = 28: 8: 10) in 2020 and 2021.

Figure 5

Dynamics of the population dynamics of key herbivorous insect, Asian corn borers (Ostrinia furnacalis) (A), and community indexes of insects on maize plants (B–E) under different fertilizer application treatments in 2020 and 2021.

Figure 6

Enzyme activity of soil nitrogen metabolism (A, B) and community indexes of soil microbes in maize field (C–F); The relative abundances of soil microbes at different phylum levels [(G)2020 and (H) 2021], and the Venn diagrams of soil microbes (I) in maize field under different fertilizer application treatments. (Different elliptical circles represented different samples in (I), and the numbers in the center and edges represent the common and unique OTUs for the five fertilizer application treatments of 100F, 90F, 80F, 62.5F and 50F. 2020: (A–E); 2021: (F–J). respectively.). (Vertical bars denote the standard error of the mean. Different uppercase and lowercase letters represent significant differences among different fertilizer application treatments in 2020 and 2021 respectively, by the LSD test at P< 0.05. The same as in the following figures).

Figure 7

Correlation analysis. ^* p< 0.05; FL, fertilizer level; MH, maize height; SD, stem diameter; RW, root weight; PW, plant weight; FSS, foliar soluble sugars; FSP, foliar soluble protein; LFFA, leaf free fatty acids, NG, glutamine oxoglutarate aminotransferase, NR, nitrate reductase; GS, glutamate synthetase; TP, total phenol; TAN, tannin; FLA, flavonoids; JA, jasmonic acid; SA, salicylic acid; JA-ILE-jasmonoyl-L-isoleucine; TGW, 1000-grain weight; Yield, grain yield; GN, grain nitrogen content; Starch, grain starch; Sugar, grain sugar; GFFA, grain free fatty acids; AA, grain amino acid content; S-UE, soil urease; S-ALPT, soil alkaline protease).

Figure 8

Effects of reduced fertilizer application on plant growth and yield of maize crop, and population abundance of key insect pests and community diversity of insects and soil microbes. (Fertilizer - 100% (Control, 100F), 90% (90F), 80% (80F), 62.5% (62.5F) and 50% (50F) NFA (normal fertilizer application) of 600 kg NPK (N: P₂O₅: K₂O = 28: 8: 10) per hectare (ha.); FFA, Free fatty acids; NR, Nitrate reductase; NADH-GOGAT, NADH-dependent glutamate synthase; JA, Jasmonic acid; SA, Salicylic acid; JA-Ile, Jasmonoyl-isoleucine).