Effects of time and rate of nitrogen application on tillering, ‘sharp eyespot’ (Rhizoctonia solani) and yield in winter wheat

Abstract

SUMMARYVarious rates of nitrogen fertilizer were applied in early and late spring to two densities of winter wheat to examine their effects on grain yield and its components. A severe attack of ‘sharp eyespot’ (Rhizoctonia solani) allowed an assessment of the effects of the treatments on the incidence of this disease.The disease level was much higher where nitrogen was applied early and increased with increase in nitrogen up to 120 units applied; it was slightly higher at the higher density. Grain yield was slightly greater where nitrogen was applied late; early application gave more, but smaller, ears. Main shoots produced at least 70% of the grain in the high-density plots but less than 50% at the low density. Tillers appearing after early March contributed little to grain yield at the higher density but substantially at the lower one. Tillers produced after early April died without heading. In general, the chances of survival of a tiller diminished with delay in the time of its appearance, but some early tillers died while later ones survived and produced ears. The chances of survival of later tillers were greater at low density and high rates of nitrogen.

Vegetative nitrogen stress decreases lodging risk and increases yield of irrigated spring wheat in the subtropics

“…Studies by Widdowson et al (1961) and Bremner (1969) in rainfed winter wheat demonstrated reduced lodging with either unchanged or increased yield associated with in-crop application of N compared with the same amount of N applied at sowing. However, their yield levels (4-5 t ha -1 ) suggested that grain yield was limited through water or nutrient limitations, and may not be applicable to modern spring wheat germplasm capable of yielding 8 t ha -1 .…”

A model of canopy development in winter wheat

“…anthesis, 90 % of the shoots born early will survive to produce ears, whereas shoots born towards the end of tillering have little chance of survival, thus resembling the pattern of tiller survival observed by Bremner (1969).…”

“…Field studies of tillering and shoot growth (Bremner, 1969;Brooking & Kirby, 1981;Masle-Meynard & Sebillotte, 1981a, 6;Fraser, Dougherty & Langer, 1982), leaf production and growth (Gallagher, 1979;Gallagher, Biscoe & Wallace, 1979;Baker, Gallagher & Monteith, 1980) and overall cereal development (Willington, 1982) have provided empirical rules of development which can be expressed mathematically and synthesized into a detailed model of canopy development.…”

Μελέτη της επίδρασης διαφορετικού βαθμού υδατικής καταπόνησης στην αναπαραγωγική ανάπτυξη εγχώριων πληθυσμών και ποικιλιών σκληρού σιταριού Triticum turgidum ssp. durum

“…Ο Hay (1986), διαπίστωσε ότι η θνησιμότητα των δευτερογενών στελεχών αυξάνει λίγο μετά την επιμήκυνση των μεσογονατίων και το στάδιο σχηματισμού του τελευταίου σταχυδίου. Επίσης, έχει βρεθεί ότι η θνησιμότητα των αδελφιών επηρεάζεται από την υψηλή θερμοκρασία (Cannell, 1969;Rawson, 1971a;Ishag and Taha, 1974;Thorne and Wood, 1987), τη διαθεσιμότητα θρεπτικών στοιχείων (Bremner, 1969;Power and Alessi, 1978;Blacklow and Incoll, 1981), την πυκνότητα της φυτείας (Darwinkel, 1978), την αλατότητα (McMaster, 1997 αλλά και από το νερό (Langer, 1979;Trought and Drew, 1980;Belford, 1981;Davidson and Chevalier, 1987;Krenzer et al, 1991;McMaster et al, 1994;Blum et al, 1990;Elhani et al, 2007). Σε διάφορα πειράματα η θνησιμότητα των δευτερογενών στελεχών που καταγράφηκε, κυμάνθηκε από 7 έως 30 % (Sharma, 1995) Ο ρόλος των νεκρών ή των μη παραγωγικών δευτερογενών στελεχών στην παραγωγικότητα της φυτείας δεν είναι ξεκαθαρισμένος (Sharma, 1995).…”