INTERACTIONS BETWEEN SOIL TEMPERATURE AND PLANT GROWTH STAGE ON NITROGEN UPTAKE AND AMINO ACID CONTENT OF APPLE NURSERY STOCK DURING EARLY SPRING GROWTH.

Authors: DONG, SHUFU - OSU, CORVALLIS, OREGON; Scagel, Carolyn; CHENG, LAILIANG - CORNELL UNIV, ITHACA, NY; FUCHIGAMI, LESLIE - OSU, CORVALLIS, OREGON; RYGIEWICZ, PAUL - US EPA, CORVALLIS, OREGON

Submitted to: Tree Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/1/2001
Publication Date: 10/1/2001
Citation: Dong, S., Scagel, C.F., Cheng, L., Fuchigami, L.H., Rygiewicz, P.T. 2001. Interactions between soil temperature and plant growth stage on nitrogen uptake and amino acid content of apple nursery stock during early spring growth.Tree Physiology. 21:541-548.

Interpretive Summary: Application of fertilizers in excess to the requirements of plants increases production costs and potentially decreases environmental quality. Effective timing of fertilizer application in relationship to the plants' ability to take up fertilizer is necessary to efficiently use fertilizers and decrease potential losses of fertilizer into the environment. With apple nursery stock, we have found that in the spring, nitrogen (N) uptake is delayed about 3 weeks after bud break. Using one-year-old 'Fuji' (M-26) bare-root apple trees we investigated whether the timing of N uptake is dependant solely on the growth stage of the tree or is a function of soil temperature. We found N uptake increased with increasing temperature and changed with tree growth stage. Before bud break, new N was not detected in trees growing in 8C soil, while N uptake increased with increasing temperatures above 12C. Ten days after bud break, new N was not detected in ntrees growing in 8C soil, while uptake continued to increase with increasing temperatures above 12C. Twenty-one days after bud break trees at all temperatures were able to acquire N from the soil, however the amount of uptake increased with increasing temperatures. The distribution of new N changed as trees grew. Most N absorbed before bud break remained in the roots however 46 days after bud break, only one-third of the N absorbed remained in the roots. Our results indicate that a combination of low soil temperature and tree developmental stage influences the ability of apple trees to efficiently take up and use nitrogen from the soil in the spring. This suggests that early fertilizer application in the spring when soil temperatures are low or when the above ground portion of the tree is not growing rapidly, may not be effective in terms of nutrient use efficiency.

Technical Abstract: Nitrogen (N) uptake by apple trees is known to be delayed until about three weeks after bud break. We used one-year-old 'Fuji' (Malus domestica Borkh) on M26 bare-root apple trees to determine whether timing of N uptake in the spring is dependant solely on plant growth stage or is a function of soil temperature. At five times during early season growth, N uptake and amino acid content was measured on trees growing at aboveground temperatures of 23/15C day/night and belowground temperatures of 8,12,16, or 20C. We found that uptake of new N increased with increasing temperature and changed with growth stage. Before bud break, 15N was not detected in trees growing in 8C soil, while 15N uptake increased with increasing temperatures above 12C. Ten days after bud break, 15N was still not detected in trees growing in 8C soil, while total 15N uptake continued to increase with increasing temperatures above 12C. Twenty-one days after bud break, trees at all temperatures were able to acquire 15N from the soil, however the amount of uptake increased with increasing temperature. Distribution of 15N in trees changed as plants grew. Most of the 15N absorbed by trees before bud break remained in the roots while 46 days after bud break, only one-third of the 15N absorbed was in the roots. Amino acid content and distribution in trees changed with growth stage but soil temperature only influenced the amino acid content in new growth. Our results indicate that a combination of low soil temperature and plant developmental stage influences the ability of apple trees to efficiently take up and use N from the soil in the spring. This suggests that fertilizer application in the spring when soil temperatures are low or when the above ground portion of the tree is not growing rapidly, may not be effective in terms of nutrient use efficiency.