Elsevier

Field Crops Research

Volume 180, 15 August 2015, Pages 110-117
Field Crops Research

Dynamic growth pattern and exploitation of soil residual P by Brassica campestris throughout growth cycle on a calcareous soil

https://doi.org/10.1016/j.fcr.2015.05.016Get rights and content

Highlights

  • We examined the effects of residual-P supply on plant growth and P uptake throughout the growth cycle.

  • The average daily rates of growth and P uptake were increased by high residual P before flowering.

  • Time to attaining maximum daily growth rate was shortened with increasing soil residual-P supply.

  • Soil residual-P supply regulated plant growth pattern, depending on growth stages.

Abstract

Plant biomass, root growth and phosphorus (P) uptake can be strongly influenced by soil P availability; large amounts of P accumulate as residual P in agricultural soils due to over-application of fertilizer P. However, the dynamics of plant growth and P uptake in response to different residual P supply gradients during the whole growth cycle is not fully understood. Here, a 2-year field experiment with Brassica campestris was conducted to characterize the dynamic pattern of biomass accumulation and P uptake rates with different residual P supply throughout the growth cycle. The plants grown in the high residual-P treatment had greater biomass production and P uptake than the low residual-P plants throughout the growth cycle. The corresponding average rates of plant growth and P uptake were higher in high than low residual-P treatments till flowering, but no differences were observed thereafter. The rates of plant growth and P uptake increased with growth stages before flowering and then decreased. The maximum differences in plant growth and P uptake rate between low and high residual-P treatments were found at the flowering stage. Compared with low P supply, high residual-P supply enhanced root dry weight over time. Time of attaining maximum average daily biomass production rate was delayed by about 4 days at low soil residual-P supply. The results indicated that soil residual-P supply intensity regulated biomass production, growth rate, P uptake rate and the time of attaining maximum average daily biomass production rate, depending on growth stages. It is suggested that exploration of soil residual P by plant is closely associated with growth stages and the soil residual P supply intensity.

Introduction

Phosphorus (P) is one of the most critical macronutrients for plant growth and development (Raghothama, 1999, Vance et al., 2003). Suboptimal P availability limits agricultural production in many regions due to P being immobile in soil (Barber and Peterson, 1995, Lynch and Brown, 2008, Cordell et al., 2009, Lynch, 2011, Johnston et al., 2014). In order to improve soil P fertility, farmers apply large amounts of chemical P fertilizers to farmlands, leading to accumulation of P in soils, while ignoring the intrinsic biological potential for efficient acquisition and exploration of soil P by crops (Ju et al., 2007, Zhang et al., 2010, Li et al., 2011, Lynch, 2011, Shen et al., 2011, Bai et al., 2013).

Plants have evolved an array of traits to acquire P from soil efficiently (Hinsinger, 2001; Lynch and Brown, 2001, Vance et al., 2003; Lynch and Ho, 2005, Lambers et al., 2006). For example, P deficiency reduced shoot demand for carbohydrates (Plénet et al., 2000) so that more carbohydrates were allocated to root growth over short time. However, in the long run, due to severely reduced leaf growth of P-deficient plants, production of carbohydrates could decrease, resulting in impaired capacity to deliver enough carbohydrates to roots (Mollier and Pellerin, 1999).

Under P deficiency roots exhibited large plasticity in order to enhance P acquisition from soil (Hodge, 2004, Lynch, 2011, Niu et al., 2013), such as reduced primary root length, stimulated formation and emergence of lateral roots and root hairs and, in selected species, cluster root formation (Williamson et al., 2001, Linkohr et al., 2002, Shen et al., 2005, Lambers et al., 2011). Hence, fully exploiting the intrinsic biological potential of plants to enhance P acquisition by roots may be critical to improving plant growth and soil residual-P exploration. However, many such studies were carried out with young seedlings grown in controlled environments for relatively short periods (Mollier and Pellerin, 1999, Lynch and Brown, 2001, Nord and Lynch, 2008, Niu et al., 2013). How soil residual-P supply intensity affects the dynamic changes in plant growth and P acquisition across the whole growth cycle under field conditions has largely been neglected so far, even though this knowledge is important for better understanding the complexity of long-term root growth responses to residual-P supply in association with final grain production and P-use efficiency.

As the capacity of roots to capture soil P is affected by soil P intensity (Teng et al., 2013, Deng et al., 2014), effective soil residual-P use strategies, such as in-season P management, should be developed based on the soil P supply in the root zone (Li et al., 2011, Shen et al., 2011, Shen et al., 2013). For optimal yield and high P-use efficiency, it is important to synchronize root-zone P supply with plant demands at the critical growth stages (Zhang et al., 2010, Shen et al., 2013). Plants require adequate P supply particularly early in growth (Grant et al., 2001, White and Veneklaas, 2012), even though only a small amount of P is absorbed in the first 2–3 weeks. More specifically, field-grown maize has total biomass and grain yield reduced due to P starvation before the six-leaf stage (Barry and Miller, 1989), and this early set-back cannot be overcome by applying more P at the later stages (Marschner, 2012). The reduced biomass and grain yield may be due to decreased root growth at the early growth stages in the environments with low P availability (Pellerin et al., 2000), indicating an important role of root growth at the early growth stage in increasing crop yield as well as regulating P supply. However, how the dynamics of root growth can be affected by a soil residual-P supply gradient during the whole growth cycle is not fully understood. We hypothesized that the dynamic pattern of root and shoot growth and P acquisition in response to different soil residual-P supply intensity varied with time.

Brassica campestris is one of the main oil rapeseed and forage crops in China (Fu, 1999, United States Department of Agriculture (USDA), 2012). The annual production of B. campestris has been more than 10 million tons since 1999, which is the highest production in the world. However, P-use efficiency of B. campestris in China is quite low (Zou et al., 2011). Better understanding of the dynamic processes of root growth, P uptake and shoot biomass accumulation in the field is needed to manipulate its intrinsic biological potential for efficient acquisition and exploration of soil P. Therefore, the objectives of the present study were (i) to characterize the dynamic processes of biomass production and P uptake with increasing soil residual-P supply gradients over the whole growth cycle in field-grown B. campestris, and (ii) to examine root growth of B. campestris in response to soil residual-P supply gradients in an intensive farming system.

Section snippets

Field experimentation

Field experiments were conducted from October to the following May for two successive cropping seasons (2010–2012) at Quzhou Experimental Station of China Agricultural University (36°52′N, 115°02′E), Quzhou County, Hebei province, China. The annual average temperature in the region ranges from 11 to 14 °C, with an annual rainfall of 450–550 mm. About 30% of precipitation falls during the B. campestris season. During the growing seasons, the total solar radiation was 2626 MJ m−2 and 2469 MJ m−2, and

Plant growth and P uptake

Shoot dry weight of B. campestris increased as soil residual-P rates increased in both years (Table 1). The increment of shoot growth due to improved soil residual-P supply varied with growth stages. Shoot biomass was significantly lower in P0 than P150 and P300, except in P150 at 23 DAF (days after formation of side shoots started) in 2012. There was no significant difference in shoot biomass between P150 and P300. Shoot biomass was significantly lower in P75 than P150 and P300 at 14 DAF in

Discussion

The time of attaining maximum average daily rate of biomass production shortened with increasing soil residual-P supply (Table 2, Fig. 2a), indicating a potential strategy to improve plant growth and exploration of soil residual-P by altering plant development of B. campestris at different soil residual-P supply. Compared with other treatments, the plant development of P0 plants was delayed (Table 2, Fig. 2a). The delayed plant development is regarded as one of the most important responses of

Conclusions

The results indicated that biomass production, growth rate, P uptake rate and the time of attaining maximum average daily biomass production rate could be modified by soil residual-P supply, depending on the growth stage. Revealing the growth pattern of B. campestris at different soil P supply helped understand the processes and develop the strategies for improving exploitation of soil residual P in the intensive farming systems.

Acknowledgments

This study was supported by the National Natural Science Foundation of China (NSFC) (Nos. 31330070, 31210103906, 31421092), the National Basic Research Program (973-2015CB150405) and the Program of Introducing International Advanced Agricultural Science and Technology of the Ministry of Agriculture of China (948 Program) (No. 2011-G18). Support for ZR was provided by DP130104825.

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