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- Author or Editor: T. W. Embleton x
Abstract
By far the most important subtropical fruit is citrus and the most widely grown citrus is the sweet orange. Lemon and grapefruit also are important citrus species. Other important subtropical fruits are dates, figs, and olives. Tropical fruits are most numerous in kinds, and a few, such as the avocado, litchi and mango are grown on a commercial scale in the subtropical regions. Others, such as bananas, pineapples, coffee, and papaya, are strictly tropical. It is not an uncommon practice to apply K, but it is done in many cases without a demonstrated need. With the realization of the broad effects of K, such a practice should not be followed, but K level should be adjusted to give optimum response for both quality and yield. For this diagnostic methods and standards are required.
Abstract
An increase in the K level in orange and grapefruit trees generally increases the thickness of the peel and reduces the percentage of juice in the fruit. Data presented in this report show that an increase in K in the lemon tree has the opposite effect as that which occurs in the orange and grapefruit tree. An increase in the level in lemon trees resulted in thinner peels and in a higher percentage of juice in the fruit.
Abstract
Field experiments in the past on Valencia orange trees in California have not shown any clear K deficiency as indicated by the effects of K applications on numbers of fruit produced per tree. Such experiments were established with little knowledge of the initial K nutritional status of the trees in question. Commercial use of citrus leaf analysis as a diagnostic tool has increased in recent years, and through this medium an orchard was found near Escondido, California with leaf K levels which indicated possible K deficiency. Some of the initial results of an experiment in this orchard are given in Table 1.
Abstract
Starch in the roots of mandarin trees (Citrus reticulata Blanco cv. Kinnow) was drastically reduced by an “on” crop. This was related to prolonged bud dormancy, delayed spring growth and an “off’ crop the following year.
Abstract
In a 5-year factorial fertilizer experiment, an increase in leaf N from 2.54 to 2.71% by soil applications of urea, reduced creasing and fruit size and increased green color on the fruit at harvest. Leaf K was increased from 0.47 to 0.67% by soil application of K2SO4 and to 0.65% by foliar application of KNO3; except for degree of fruit color and leaf N content, effects of soil- and foliar-applied K differed little and both increased yield, fruit size, and green color on the fruit and reduced creasing. Increasing leaf P from 0.132 to 0.139% had little influence on factors influencing the value of the fresh-fruit crop. Gibberellic acid (GA) sprays increased green color on the fruit and reduced creasing. The effects of N, K, and GA on reducing creasing and increasing green color on the fruit were strongly additive. There was an inverse relation between creasing and green color of fruit. Each problem can be reduced but at the expense of the other, and both problems cannot be reduced simultaneously. Packinghouse statements showed that monetary returns/tree were increased about 75% by K treatments without GA; 17% with GA alone; 61% with GA + soil-applied K; and 42% with GA + foliar-applied K.
Abstract
Where Mg deficient ‘Washington’ navel orange trees were sprayed with Mg, leaf Mg was increased from a deficient to an optimum level in the first year of application. However, it was not until the fourth year of application that a yield increase occurred. At least 2 sprays annually were required. There was an increase in total soluble solids in the juice as a result of the sprays, but there were no other consistent effects on fruit quality. Magnesium in the feeder roots was increased by the foliage sprays. Leaf K was decreased by the Mg sprays. One year after cessation of the sprays the leaf Mg was again in the deficiency range.
Abstract
Sprays of ammonium ethyl carbamoyl-phosphonoate (Krenite), applied to the tops of mature Lisbon lemon trees [Citrus limon (L). Burml.] resulted in significant inhibition of re-growth for over 3 years. One spray increased yield over the control trees (hand topped annually), while 2 sprays reduced yield. The sprays did not effect the N concentration in the leaves.
Abstract
‘Prior Lisbon’ lemon trees were treated with increasing rates of N fertilizer up to 6 lb. N per tree per year. Likewise, ‘Monroe Lisbon’ lemon trees were treated with up to 4 lb. N per tree per year. Also, for the Trior Lisbon/one treatment was 6 urea foliage sprays per year which supplied about 2 lb. N per tree per year. For the Trior Lisbon’ there was a tendency for yields to increase with increasing N rates with the high rate yielding significantly more than the low rate. Yield was highly correlated with leaf N with maximum yield occurring at about 2.2% leaf N. Urea foliage sprays maintained leaf N and maximum yield. Fruit quality was not adversely affected by increasing N. As with Prior ‘Lisbon’, ‘Monroe Lisbon’ yields increased with increasing N but the maximum yield occurred at about 2.5% leaf N. Yields from single N applications were not different from split N applications.
Abstract
Carbohydrate (CHO) accumulation in ‘Valencia’ orange leaves, sampled in February, was inversely related to the fruit load on the tree at the time of sampling but directly related to the amount of fruit produced from the flowering which followed the time of leaf sample. Late harvest reduced fruit production in the following year but did not significantly alter CHO accumulation.
Abstract
Reference values were derived from field data for use in evaluating the N, P, K, Ca, and Mg status of ‘Valencia’ orange (Citrus sinensis [L.] Osbeck) trees by the Diagnosis and Recommendation Integrated System (DRIS). DRIS diagnoses generally agreed with diagnoses made by the sufficiency range method, with the advantage that DRIS reflects nutrient balance, and identifies the order in which nutrients are likely to become limiting. DRIS diagnoses were affected by the type and age of the tissue sampled. DRIS reflected changes in nutrient concentrations due to alternate bearing or crop load effects and agreed with the sufficiency range method when concentration changes were sufficient to affect the latter method.