Efficacy of Treatments for Delaying Senescence of Wheat Leaves: II. Senescence and Grain Yield under Field Conditions

Abstract

Longevity of leaves directly influences grain yield of wheat (Triticum aestivum L.), but is greatly diminished by environmental stresses. The objective of these studies was to identify treatments that might delay senescence of wheat leaves and increase grain yield. ‘Nesma’ wheat was grown on a heavy clay soil at Meknes, Morocco, for two seasons, the first characterized by mild stress and the second by more severe stress from inadequate precipitation and high temperature. Three planting dates, two seeding rates, and foliar applications of NH4NO3, and KH2PO4 in randomized complete block designs were tested for efficacy in delaying senescence of leaves as measured by proteolytic activity, chlorophyll and protein concentrations, and grain yield. Advancing the planting date from early December, the optimum time, to November in the first year and delaying planting until January in the second year reduced grain yields in both seasons. Increasing the seeding rate from 200 to 400 kernels in m‐2 increased grain yields only in the second year, and foliar applications of 10 kg N as NH4NO3 ha−1 were ineffective in both years. Foliar applications of 5 to 10 kg ha−1 KH2PO4, in contrast, often increased grain yields by 1 Mg ha−1 or more. Senescence processes were enhanced by late planting because of high temperatures during maturation and by dense seeding because of interplant competition. Treatments that increased grain yields usually slowed senescence processes. Applying dilute solutions of KH2PO4 was most effective and, after further testing, might have merit for wheat in regions where drought and high‐temperature environmental stresses occur.

Potential for foliar phosphorus fertilisation of dryland cereal crops: a review

“…While the number of fertile tillers and grains has been determined before anthesis (Elliott et al 1997), it appears that in some instances an application of P after anthesis does have the capacity to increase yield through increased grain fill. Benbella and Paulsen (1998) found that applications of P to wheat after anthesis increased yield while Gray (1977) reviewed several experiments that showed yield responses to foliar P applications after anthesis.…”

“…Based on our review of the literature the most appropriate timing for application is at early pod development in soybeans (Gray 1977), from canopy closure to anthesis in cereal crops (Benbella and Paulsen 1998;Mosali et al 2006;Girma et al 2007) and early tasseling in maize/corn (Harder et al 1982;Giskin and Efron 1986;Girma et al 2007). The rate of application is dependent on crop requirement, crop type, number of applications, water volume and salt loading but in general 1.5-4 kg P ha -1 gave the best results (Benbella and Paulsen 1998; Mosali et al 2006;Girma et al 2007).…”

Response of Chlorophyll, Carotenoid and SPAD-502 Measurement to Salinity and Nutrient Stress in Wheat (Triticum aestivum L.)

“…This period is known as the lag phase, during which cellular division is rapid and endosperm cells and amyloplasts are formed, and is considered very sensitive to environmental stresses [125].…”

CN-Wheat, a functional–structural model of carbon and nitrogen metabolism in wheat culms after anthesis. II. Model evaluation

“…This trade-off is under environmental control but also depends on the genotype, as illustrated by the stay-green behaviour of some crop cultivars. These are characterized by their ability to maintain significant areas of vegetative tissues that are still photosynthetic at maturity (Benbella and Paulsen, 1998;Borrell et al, 2001), but the underlying mechanisms remain unclear.…”