Influence of Nitrogen Application Time on Nitrogen Absorption, Partitioning, and Yield of Pecan

Abstract

<jats:p>Nitrogen was applied to mature pecan (<jats:italic>Carya illinoinensis</jats:italic> Wangenh. C. Koch.) trees annually as a single application at 125 kg·ha<jats:sup>-1</jats:sup> N in March or as a split application with 60% (75 kg·ha<jats:sup>-1</jats:sup> N) applied in March and the remaining 40% (50 kg·ha<jats:sup>-1</jats:sup> N) applied during the first week of October. Nitrogen treatment did not affect yield, and had little effect on the amount of N absorbed. Nitrogen absorption was greater between budbreak and the end of shoot expansion than at other times of the year. Substantial amounts of N were also absorbed between leaf fall and budbreak. Little N was absorbed between the end of shoot expansion and leaf fall, or tree N losses met or exceeded N absorption. Pistillate flowers and fruit accounted for a small portion of the tree's N; ≈0.6% at anthesis and 4% at harvest. The leaves contained ≈25% of the tree's N in May and ≈17% when killed by freezing temperatures in November. Leaves appeared to contribute little to the tree's stored N reserves. Roots ≥1 cm diameter were the largest site of N storage during the winter. Stored N reserves in the perennial parts of the tree averaged 13% of the tree's total N over a three year period. Current year's N absorption was inversely related to the amount of stored N, but was not related to the current or previous year's crop load.</jats:p>

Pecan Leaf Elemental Sufficiency Ranges and Fertilizer Recommendations

“…Trees also conserve many nutrients from leaves as they enter dormancy that are used during subsequent years (Acuña-Maldonado et al, 2003;Smith, 2009;Smith et al, 2007)characteristics that can be portrayed by tissue elemental concentrations, but not by soil analysis. Another problem encountered when trying to represent nutrient availability with soil samples is that fertilizers may not be distributed equally over the entire orchard floor.…”

Influence of Cluster Thinning on Return Bloom, Nut Quality, and Concentrations of Potassium, Nitrogen, and Non-structural Carbohydrates

“…Scientists have also speculated that the amount of stored N might be closely associated with alternate bearing (Goff et al, 2001;Kraimer et al, 2004;Wood, 2001a), although studies on pecan have shown little response or a negative response to fall applied N (Acuña- Maldonado et al, 2003;Smith et al, 2004). Because K plays a critical role in carbohydrate and N transport, we also monitored root concentrations to determine if K was associated with crop thinning.…”

“…Nitrogen was not limiting in this study, yet trees displayed classic alternate bearing. Pecan trees store large quantities of N that can be mobilized on the basis of demand (Acuña-Maldonado et al, 2003). Fruit typically remove a relative small amount of the tree's N. Pecan trees that are adequately supplied with N are unlikely to respond to fall-applied N, especially when it is common to require two or more years to reduce yield by withholding N (Smith, 2002;Worley, 1974Worley, , 1990.…”

“…There are conflicting reports regarding the benefit of fall N application. Acuña-Maldonado et al (2003) reported the greatest N absorption between budbreak and the end of shoot expansion, with little absorption between the end of leaf expansion and leaf fall. Kraimer et al (2004) later reported that N applied during the kernel filling stage was strongly absorbed.…”

Pecan Nutrient Element Status and Orchard Soil Fertility in the Southeastern Coastal Plain of the United States

“…Critical leaf sufficiency ranges vary considerably by geographic region and state extension service recommendations (Pond et al, 2006). Crop load (Acuna-Maldonado et al, 2003;Kraimer et al, 2001Kraimer et al, , 2004Smith et al, 2007), soil type, and environmental conditions (Johnson and Raun, 2003) can affect nutrient availability, uptake, and/or tissue concentration. Pond et al (2006) suggest that regional nutrient sufficiency ranges should be considered to ensure accurate nutritional diagnoses.…”