Comparative Response of Huanglongbing-Affected Sweet Orange Trees to Nitrogen and Zinc Fertilization under Microsprinkler Irrigation

Abstract

Nitrogen and micronutrients have a key role in many citrus plant enzyme reactions. Although enough micronutrients may be present in the soil, deficiency can develop due to soil depletion or the formation of insoluble compounds. The objectives of this study were to (1) determine the adsorption, distribution, and availability of Zn in a sandy soil; (2) compare the effectiveness of foliar and soil application methods of Zn on Huanglongbing [HLB] affected trees; (3) compare foliar application rates of Zn for HLB-affected trees; (4) determine the effect of N rates on yield, soil inorganic N distribution patterns, and tree growth parameters. Tree rows were supplied with three N rates of 168, 224 and 280 kg·N·ha−1 and Zn at single and double recommended rates (recommended rate = 5.6 kg·Zn·ha−1) using foliar and soil application methods, in a split-plot experimental design. The results show that Zn concentration in the 0–15 cm soil depth was three times higher than the 30–45 and 45–60 cm soil depths during the study. An adsorption study revealed high Zn (KD = 6.5) sorption coefficients at 0–15 cm soil depth, while 30–45 and 45–60 cm depths showed little sorption. Leaf Zn concentration for foliar spray was two times higher than the soil application method. A nitrogen level of 224 kg N ha−1 improved canopy volume when compared to other N levels at the expense of reduced fruit weight. Foliar Zn application at 5.6 or 11.2 kg ha−1 and N rate at 224 kg ha−1 appear to be adequate for improving the performance of HLB-affected citrus trees.

The Effect of Foliar and Ground-Applied Essential Nutrients on Huanglongbing-Affected Mature Citrus Trees

“…The sample was capped and shaken for 5 min at a high rate (200 reciprocating per minute). Subsequently, the supernatant was allowed to rest for 30 min, after which the solution was filtered onto labeled vials, and stored in a freezer pending analysis [ 12 , 14 , 48 ]. Mehlich III-extractable concentrations of P and heavy metals were processed using inductively coupled plasma optical emission spectroscopy (ICP-OES, Spectro Ciros CCD, Fitzburg, MA, USA).…”

“…HLB alters citrus tree physiology (photosynthesis and xylem flux) and morphology (e.g., phloem translocation, bloated and corky veins, root length, and density) subsequently affecting nutrient acquisition, movement, and utilization [ 10 , 11 ]. Several methodologies were devised that include soil acidification, enhanced nutritional programs, split fertigation, and foliar spray of essential nutrients to reverse the decline of citrus trees as the result of HLB-induced citrus deterioration [ 7 , 12 , 13 , 14 , 15 ].…”

“…Nitrogen is one of the essential nutrients for citrus production that play a vital role in canopy growth and fruit yield [ 14 , 24 ]. Florida sandy soils coupled with leaching rain events and extended irrigation duration exacerbate the possibility of N leaching beyond the root zone [ 12 , 25 , 26 , 27 ].…”

Sap Analysis: A Powerful Tool for Monitoring Plant Nutrition

“…trees productive and the growers in business in the Huanglongbing (HLB) or citrus greening era [5][6][7][8][9][10][11]. However, some growers are applying more nutrients than needed to compensate for the negative effects of HLB [12][13][14][15][16]. An excessive fertilization strategy can reduce profitability and damage the environment due to groundwater contamination, eutrophication, and change in microbial dynamics [2,12,[17][18][19].…”

“…A large portion of the studies focused mainly on N and greenhouse crops [2,28,29,47]. Still, little research has been conducted with micronutrients, which seem to alleviate the effect of plant diseases such as HLB in citrus [6,15,16].…”