Combined effects of partial root drying and patchy fertilizer placement on nutrient acquisition and growth of oilseed rape

Abstract

Partial rootzone drying (PRD) is widely investigated as an effective irrigation technique, resulting in higher water use efficiency and yield for plants growing under mild water deficit. Nutrition is another important factor affecting plant yield, but nutrient acquisition has only rarely been considered in conjunction with PRD. Here we investigate the interaction between water and fertilizer supply in a pot experiment with oilseed rape (Brassica napus L.). Eight treatments were set up for the experiment, a factorial combination of four watering regimes (100% control watering at both sides of the plants; 50% control watering at both sides of the plants; 50% fixed watering applied only to one side of the plants; 50% alternate watering applied alternately to both sides of the plant) and two fertilizer placement levels (uniform over the entire pot, and patchy supplied to one side). For the 50% watering treatments, the total amount of water supplied to the plants was the same, only the pattern of application differed between treatments. Also the total fertilizer applied was the same for all treatments. Oilseed rape roots foraged effectively for water and nutrients resulting in relatively small differences in nutrient uptake and above-ground growth among the water-deficit treatments. Placing fertilizer at one side of the plants increased nutrient uptake, but there were differences between the water treatments and interactions with water uptake. Alternate watering resulted in the highest growth, as a result of the largest nitrogen and phosphorus uptake with the smallest root investment among the three water deficit treatments. Fixed watering resulted in poorest performance when fertilizer was uniformly spread throughout the pot, because the plants were unable to acquire the nutrients on the dry side. Our results show that PRD can be well combined with patchy fertilizer supply, but that reduced nutrient uptake may be expected when nutrients are supplied in parts of the soil volume that remain too dry.

Effects of Varied Nitrogen Supply and Irrigation Methods on Distribution and Dynamics of Soil NO3-N during Maize Season

“…Thus, NO 3 -N in 40-60 cm under NP might become an ideal N source for absorption when plants are in dire need of N nutrition. This compares well with the findings that the enhanced decrease of NO 3 -N in local area was closely related to the improved root growth (Wang, de Kroon, & Smits, 2007). These suggested that dynamics of soil NO 3 -N were related to the supply of N and water, crop N requirement and the root growth.…”

Root foraging and yield components underlying limited effects of Partial Root-zone Drying on oilseed rape, a crop with an indeterminate growth habit

“…Another conspicuous feature from our measurements of SWC in both experiments is that dry roots occasionally develop in all treatments, not only when partial root-zone drying is induced (see also Wang et al 2007). In our Phytotron plants grew under nearambient conditions, and our water regimes reflected current crop practices under partial root-zone drying.…”

“…As plants did not flower in our previous experiments (Wang et al 2005(Wang et al , 2007 we do not know whether seed yield is affected similarly as vegetative growth. In a crop as oilseed rape with an indeterminate growth habit in which the reproductive growth phase largely overlaps with the vegetative growth phase, these phases may respond differently to environmental conditions.…”

“…Huyou 15 was used in this study as in our previous studies (Wang et al 2005(Wang et al , 2007. This variety of oilseed rape is developed in the middle and lower reaches of Changjiang River in monsoon climate (Sun et al, 2002;Zhang and Yu 2003), where the crop is grown in the dry period of winter and spring.…”

“…Our previous greenhouse studies revealed that oilseed rape roots were able to forage for fixed water patches by selective root placement (Wang et al 2005(Wang et al , 2007. Fixed watering and alternate watering generally outperformed uniform watering in terms of vegetative growth, as a result of effective root foraging and enhanced water use efficiency, respectively.…”