Abstract
Exponential fertilization is well-known for improving the growth and nutritional status of seedlings during nursery culture. However, less is known about how genetic variability among seedling species influences the effects of fertilization regimes on the growth of seedlings and their nutritional status under varying fertilization levels. Here, we conducted a greenhouse experiment to compare the growth, as well as the nitrogen (N) and phosphorus (P) nutrient concentration responses, of 2- and 3-generation Chinese fir (Cunninghamia lanceolata (Lambert) Hooker) seedlings to the impacts of varying exponential and conventional constant-rate fertilization levels (50, 100, and 200 mg P seedling−1). Seedling size and shoot:root ratios were lower in exponential fertilization than in conventional fertilization. Exponentially fertilized seedlings had higher concentrations of N and P nutrients compared to conventionally fertilized seedlings during low-level fertilization. Conversely, an elevated P concentration was observed in seedlings subjected to conventional fertilization compared to those exposed to exponential fertilization during high-level fertilization. However, there were no significant differences in seedling N and P concentrations between the two fertilization regimes during medium-level fertilization. Furthermore, 2- and 3-generation Chinese fir seedlings differed greatly in their growth and nutritional status. Additionally, there were significant fertilization regime × seedling generation interaction effects on the seedling shoot:root ratio and N concentration. Our findings suggest that exponential fertilization can improve the nutritional status, survival, and growth of Chinese fir seedlings, especially on competitive sites, and that information on both intra-species genetic variability and appropriate fertilizer levels is necessary for the successful fertilization of Chinese fir seedlings, regardless of fertilization regimes.
Highlights
Nursery stock quality determines the survival and growth rates of out-planted seedlings, thereby subsequently enhancing forest productivity [1]
Our findings suggest that exponential fertilization can improve the nutritional status, survival, and growth of Chinese fir seedlings, especially on competitive sites, and that information on both intra-species genetic variability and appropriate fertilizer levels is necessary for the successful fertilization of Chinese fir seedlings, regardless of fertilization regimes
This study demonstrates that exponential fertilizer loading can lower the growth rate of Chinese fir seedlings, but may improve their internal N and P nutrient reserves during nursery culture, especially at low-level fertilization
Summary
Nursery stock quality determines the survival and growth rates of out-planted seedlings, thereby subsequently enhancing forest productivity [1]. Forests 2019, 10, 719 interspecies variations in the nutrient use efficiency rate have been documented [5,6,7], it is necessary to clearly understand the responses of the nutritional status of different plant species to fertilizer loading from fertilization regimes. Exponential nutrient loading is a new fertilization technique that has been widely applied to induce steady-state luxury nutrient consumption in seedlings by fertilizing them at exponential rather than conventional (constant) rates, thereby providing nutrient concentrations that more closely match plant requirements during their exponential growth phase [8,10,11,12,13,14]. Seedling morphological and physiological characteristics have revealed varied responses among species to fertilizer loading via an exponential fertilization regime
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