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Abstract
This is a report of a 4 × 4 NK factorial experiment over a 6-year period using ‘Hamlin’, ‘Pineapple,’ and ‘Valencia’ orange trees [Citrus sinensis (L.) Osbeck] on rough lemon rootstock (Citrus jambhiri Lush.) planted on Astatula f.s., formerly classified Lakeland f.s. Main effects of N and K were considered independently because interactions were not significant for most measurements. Increases in N rate increased the juice content and acid, whereas increases in K resulted in higher acid and lower soluble solids with an accompanying lower soluble solids/acid ratio. Smaller sized fruit, more green fruit, and a lower packout were a result of increased N rates. Increased K rates did not influence external characteristics of the fruit other than producing larger fruit. Rind blemishes occurred more often at the low N rate and diminished as the N rate increased. Incidence of decay in storage was greatest at the lowest N rate. Creasing was found to be significantly related to high N and low K rates.
Abstract
A 5-year field experiment planted on Astatula fine sand using ‘Hamlin,’ ‘Pineapple,’ and ‘Valencia’ orange (Citrus sinensis [L.] Osbeck) on rough lemon rootstock (Citrus jambhiri Lush.) with 4 levels each of N and K indicated that higher N rates increased fruit production and yield of soluble solids. High K applications decreased soluble solids. Increase in tree canopy area between 1968 and 1974 was related to N but not to K applications. Maximum yield response with N in all 3 cultivars was attained at 202 kg/ha/yr. ‘Hamlin’ orange showed maximum yield response to K at 167 kg/ha/yr whereas ‘Pineapple’ and ‘Valencia’ orange had maximum yield at 112 kg/ha/yr. Leaf analyses showed that increased N application resulted in higher leaf N and Mg contents but lower P and K levels. Increased K application showed higher P and K levels but lower Ca and Mg levels.
Abstract
Six year’s data with so-called ‘Temple’ orange (Citrus hybrid) on ‘Cleopatra’ mandarin rootstock (Citrus reticulata Blanco), show that increased rates of N and K increased fruit yield. P also increased yield. Spring vs. fall irrigation resulted in a significant increase in fruit production in 1 of 6 years, although slightly higher fruit production was observed every year with spring irrigation. Increased N rates resulted in higher leaf N and Mg but lower leaf P, K, and Ca. Increased K rates raised leaf K but lowered leaf Mg. The addition of P in the fertilizer resulted in higher leaf P and Ca but lower K and Mg contents. Spring irrigation induced lower K but higher Mg in certain years.
Abstract
The temperature field around a wind machine located in a citrus orchard was measured using a fast response thermistor network. The area of protection provided by the wind machine was kidney-shaped. Temperature at any given point was continually rising or falling and depended upon the position of the point relative to the jet. Maximum temperature rise was recorded 90 to 150° after the jet had passed the point.
Air movement was not always away from the machine, but cold air inflow occurred just in advance of the turning jet. The wind machine protected a citrus orchard on radiation nights, provided a relatively stable condition existed in the lower atmosphere. The machine caused downward movement of warm air from aloft by creating divergence of cold, dense air at lower levels.
The area and degree of protection were directly related to the inversion strength, strong inversions producing a greater effect than weak inversions. A larger area of protection was obtained under conditions of weak inversions at the lower elevation (5 ft) without leaves than when leaves were present. However, a greater area of protection was obtained under strong inversions when leaves were present on the tree. Thus, one might expect less area of protection in defoliated groves, i.e. groves which had been defoliated by earlier freezes and had not refoliated, or in deciduous orchards before leafing.
Abstract
Increased N and K rates resulted in higher acid content in juice of ‘Temple’ orange (Citrus hybrid). P fertilization lowered both soluble solids and acid contents, but the influence on acid was more pronounced as it was reflected in higher soluble solids-acid ratio. High N vs. low N treatment also caused a small but consistent reduction in juice content. Spring irrigation resulted in higher soluble solids content than fall irrigation. N treatments decreased and K treatments increased both fruit size and weight; irrigation treatments showed no consistent trends. High N and spring irrigation treatments caused increased intensity of orange color in rind. Incidence of creased fruit was increased by high N, low K, and spring irrigation treatments. No consistent trends were found in fruit storage decay with grove treatments and the data were significant only in certain years.
Abstract
The ‘Murcott Honey Orange’ is grown rather extensively in Florida and is highly desired because of its fine flavor and dark orange colored flesh. Its origin is unknown, but the ‘Murcott’ is probably a hybrid of mandarin and sweet orange parentage. This variety bears very heavy crops with much of the fruit set in clusters. These extremely heavy crops result in a collapse of the trees near the time of fruit maturity. Depending on the severity of this decline, the trees may require from one to several years to recover (Figs. 1,2,3) or in extreme cases, die. The leaves and fruit from severely affected trees turn yellow and drop followed by dieback of the branches. These symptoms appear in December and January and become progressively worse as the fruit matures. Fruit on less severely affected trees are usually small and fail to develop the dark orange color characteristic of the variety. The problem of ‘Murcott’ collapse is probably the main reason this variety is not more widely grown. Knorr and Collins (1) previously described this condition and reported that in some cases, severe root deterioration occurs. The problem apparently is not limited to ‘Murcotts’ since similar symptoms have been reported in California for the ‘Wilking’ and ‘Kinnow’ mandarins (3).
Abstract
Applications of lead arsenate to ‘Temple’ oranges lowered the titratable acid content but not the soluble solids or percentage juice. The percentage total decay, peel injury, and creasing were not appreciably influenced by the lead arsenate sprays. Fruit from trees sprayed with lead arsenate passed legal maturity standards 15 to 20 days earlier than fruit from non-sprayed trees.
Abstract
Arsenic (As) and lead (Pb) sprays applied to grapefruit (Citrus paradisi Macfad.) accelerate fruit maturity but do not contribute to the As and Pb content of the peel oil. The physicochemical properties of the expressed oils are influenced by this induced maturity but would occur naturally in the course of normal fruit maturation.
Abstract
An N rate associated with reduced fruit production substantially reduced the quantity of peel oil on a per metric ton (MT) of fruit basis and the yield of oil on a per hectare basis of ‘Pineapple’ orange (Citrus sinensis (L.) Osbeck) K had no significant effect on the peel oil content on a per ha basis, but did increase fruit production (MT/ha) and reduced the peel of oil content.
Abstract
Yields and quality were compared on young bearing ‘Bearss’ lemon (Citrus limon L.) trees grown with 3 rates of N and K and 2 levels of soil moisture over a 4-year period. Increased rates of N application increased fruit production, incidence of fruit with scab, and green fruit; and decreased acid content of juice. Potassium applications increased the acid content of juice. Irrigation increased fruit size and decreased the number of green fruit after curing. A leaf N content of 2.2 to 2.6% is suggested for optimum fruit production for ‘Bearss’ lemon under Florida conditions.