Hunger Signs in Crops

Sprague, Howard B.

doi:10.1097/00010694-196409000-00014

Cited by 74 publications

(45 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…If there is a deficiency in a mobile element, such as nitrogen or phosphorus, senescence of older leaves occurs, but younger leaves remain healthy, presumably because of nutrient remobilization from the older leaves. In contrast, if there is a deficiency in a non-mobile element, such as calcium, only the young leaves are affected (Sprague, 1964). More recent work has shown that nitrogen nutrition during leaf development greatly influences not only lifespan but the rate of senescence (Makino, Mae & Ohira, 1984).…”

Section: Water and Mineral Relationsmentioning

confidence: 99%

Gene expression during leaf senescence

1994

View full text Add to dashboard Cite

SUMMARY Leaf senescence is a hiphly‐controlled sequence of events comprising the final stage of development. Cells remain viable during the process and new gene expression is required. There is some similarity between senescence in plants and programmed cell death in animals. In this review, different classes of senescence‐related genes are defined and progress towards isolating such genes is reported. A range of internal and external factors which appear to cause leaf senescence is considered and various models for the mechanism of senescence‐ initiation are described. The current understanding of senescence at the wrganelle and molecular levels is presented. Finally, same ideas are mooted as to why senescence occurs and why it should be studied further.

show abstract

Section: Water and Mineral Relationsmentioning

confidence: 99%

Gene expression during leaf senescence

1994

View full text Add to dashboard Cite

show abstract

“…The arithmetic average was applied because of the representivity of the samples for each locality. Thirty percent are in the hidden hunger range (Sprague, 1964) respectively. These results should make farmers and agriculturalists aware of the possibility that K may limit maize yields and motivate them to have their soils regularly analyzed for K.…”

Section: Resultsmentioning

confidence: 99%

“…Walker and Parks (1969) and Melis and Farina (1984) found that when K becomes insufficient for normal growth at low extractable K values, lodging of maize occurred. Sprague (1964) stated that as K deficiency becomes more severe leaf margins die, and ears are tapered and not completely filled resulting in lower yields. Barnard and du Preez (2004) indicated an overall loss from South African cultivated soils of 87 693 t K during the ten year period [1965][1966][1967][1968][1969][1970][1971][1972][1973][1974][1975].…”

Section: Threshold Values and Sufficiency Levels For Potassium In Maimentioning

confidence: 99%

Threshold values and sufficiency levels for potassium in maize producing sandy soils of South Africa

Biljon

Fouche

Botha³

2008

South African Journal of Plant and Soil

View full text Add to dashboard Cite

South African maize farmers apply only two thirds of the potassium (K) which is annually removed in the grain, causing a deficit of more than 13 000 tons K per season. It is expected that these maize fields will gradually become depleted and more K will be required to maintain or improve yields. Research goals were set for sandy soils in the main maize producing areas of South Africa to determine the lower & upper threshold values and sufficiency levels for soil K, the K status of these soils and to evaluate the sufficiency level concept for K at the various localities in the Free State Province. Field experiments were conducted at nine localities during four consecutive seasons. The experimental data included the soil K extracted with NH 4 OAc and the relative maize yields (RY) of the treatments, +K which received macro, secondary and micro nutrients and 0K which received the same nutrients but K was omitted. The results indicated a lower threshold value of 125 mg K kg -1 below which maize is expected to respond positively and an upper threshold value of 190 mg K kg -1 above which maize is expected not respond to additional K. The extractable K from 25 000 sandy soil samples received from maize farmers indicated that approximately 50% of these samples contained less K than the lower threshold value, approximately 30% was between the lower and upper threshold values and the remaining 20% was above the upper threshold value. The sufficiency levels obtained with the Mitscherlich model at 98% RY, ranged from 109-340 mg K kg -1 . The difference between the sufficiency values and the extractable soil K at any of these localities, gives an unbiased measurement of the K fertilizer to be recommended.

show abstract

“…This poor growth was attributed to a N deficiency (Sprague 1964) , possibly through volatilisation of ammonia, from the added (NH 4) 2S04' To offsetN losses in this form, additional Nand K, each equivalent to 56 kg/ha, were added 30 days after sowing, which improved leaf colour. In Experiment 2 N was added mainly as a nitrate to avoid the loss of N by this means from the calcareous soils.…”

Section: Methodsmentioning

confidence: 99%