Early-sown Crops Research Articles

Effect of sowing date and seed rate on crop development and grain production of winter wheat.

In a field trial in 1973-5, winter wheat cv. Lely was sown on 3 dates at 3- to 4-wk intervals from end-Sept. at low (80-90 kg seed/ha) or high (160-180 kg seed/ha) sowing rates. Delaying the sowing date decreased grain yield. This decrease was caused by a smaller number of grains/ear and a lower grain wt. Sowing rate had a positive influence on the number of ears, but a negative effect on the number of grains/ear and the grain wt. With early sowing, sowing rate was found to have no effect on grain yield, due to mutual compensation of changes in yield components. With late sowing, a higher sowing rate increased the number of ears so much that a higher grain yield was achieved. The grain yield/ear depended on the age of the tiller. Tillers that emerged earlier produced more and heavier ears. The number of grains/ear and the grain wt. could be related to the rate of development of the ear-bearing shoot. The pattern of tillering was affected by the sowing date. With early sowing, most tillers emerged in autumn and winter, whereas the late-sown wheat tillered in spring. Also, the early-sown crop consisted largely of ears from early tillers, whereas the late-sown one had many ears from late-formed tillers. (Abstract retrieved from CAB Abstracts by CABI’s permission)

The quality and quantity of forage oats sown at intervals during autumn: effects of nitrogen and supplementary irrigation

The quality and production of forage oats (Avena sativa cv. Acacia) sown on five occasions between late summer and late autumn was measured in an experiment near Armidale, New South Wales. Additional treatments were nil vs. 71 kg ha-1 nitrogen (N) and non-irrigated vs. supplementary irrigation. Nitrogen fertilizer did not significantly affect plant establishment, or the dry matter or digestible organic matter production from any sowing. Plant establishment declined linearly in association with reductions in the mean ambient temperature during the ten days after sowing. Crops sown on February 25 and March 13 produced at least 35 per cent more forage (P < 0.05) with irrigation than dryland crops but with all later sowings the effect of irrigation was not significant. Early sown crops contained up to 36 per cent senescent leaf and 44 per cent dead leaf in August. Organic matter digestibility contents of green and senescent forage differed little and always exceeded 69 per cent, but that of the dead leaf was at times as low as 45 per cent. Equations are presented relating digestible organic matter available in irrigated and non-irrigated treatments to the length and mean temperature of the growth period.

Time of sowing and wheat yield in northern New South Wales

The influence of variation in time of sowing on grain yield in five wheat cultivars has been studied in the North West Slopes of New South Wales over the period 1967 to 1971. Highest grain yields were obtained when wheat was sown at the end of June so as to flower at the end of the first week in October. Reductions in relative grain yield of 5 to 7 per cent were recorded for each week that sowing was delayed after the end of June, or 9 to 13.5 per cent for each week that flowering was delayed after the first week in October. Lower grain yields from late sown crops were associated with lower leaf area duration after flowering which could account for 69 per cent of the variation in grain yield. Lower grain yields in early sown crops were associated with lower ear numbers which could be ascribed in part to the influence of frosts.

Incidence and Damage Severity of Pod Borer, <i>Helicoverpa Armigera</i> (Hubner) in Chickpea (<i>Cicer Arietinum</i> L.)

Incidence, population fluctuations and damage severity of pod borer, Helicoverpa armigera (Hubner) chickpea was studied at Regional Agricultural Research Station, Ishurdi, Pabna, Bangladesh during rabi crop seasons of 2003-04 and 2004-05. The incidence started in 2nd to 4th week of January irrespective of sowing dates. The borer population fluctuated depending on the dates of sowing. Pod borer population was higher in the early sown crops (October 15 to November 01) and with delayed the dates of sowing from November 01 to 30 population was decreased and then increased again. It was observed that both the early (October 15 to November 01) and late sown (December and onward) crops received higher pod borer damage and produced lower yield. But mid sown (November 08 to 30) crops received less pod borer damage and produced higher yield. Hence, for ensuring higher yield with less pod borer damage, chickpea should be sown within the range of November 08 to 30 and the best date of sowing seems to be November 15. Key words: Chickpea, Pod borer, Population fluctuation, Damage severity, Yield. DOI: 10.3329/bjsir.v44i2.3676 Bangladesh J. Sci. Ind. Res. 44(2), 221-224, 2009

Time of sowing and wheat production in southern NSW

Wheat (CV. Heron) sown on clover-improved soils at Wagga Wagga, New South Wales, over the period 1961 to 1965 showed a general reduction in yield and an increase in grain protein percentage with delay in sowing. Grain yield decreased by 3.7 per cent for each week's delay in sowing after the end of April and the rate of grain protein increase ranged from 0.09 to 0.56 per cent for each week's delay, depending on seasonal conditions. This grain protein increase was accompanied by a reduced kernel size which resulted in a decrease in grain protein yield of 12.5 lb an acre for each week's delay in sowing. The reduced grain yield with later sowings was associated with less efficient use of soil moisture the post-flowering period. Although the cumulative evapotranspiration of early sown crops was about two inches greater than that for late sown crops in mid-spring, all sowings reduced the soil moisture potential to -15 bars to a depth of four to five feet at maturity. However, the late sown crops matured more rapidly with a reduction in all yield components. Changes in soil mineral nitrogen concentration during the growing season indicated that there Was adequate nitrogen available for all sowings. In two years mineralization of soil organic nitrogen occurred under the crops and contributed significantly to the crops requirement. In a third year mineral nitrogen losses from the soil could not be accounted for by plant uptake.

Studies on the biology and control of pests of seed beans (Phaseolus vulgaris) in northern Tanzania

Light-trap catches of Heliothis armigera (Hb.) reach peaks during the wet seasons, April and November–January. Initial infestation of seed beans by H. armigera occurs in April–May at the time of flowering of the early-sown crop, the adults probably originating from an earlier generation on maize. Two generations are completed during the main seed bean season, the first on early-sown beans and the second on later beans, and the dry period July–October may be passed in pupal diapause. Damage, caused by the older larvae eating the seeds in the pod, is prevented by spraying the young larvae with DDT (25% e.c. at 3 pt/2 gal spray/acre) (the standard treatment) or endosulfan (35% e.c. at 1½ pt/2 gal spray/acre) at about six weeks after the beans emerge.Adults of the Pentatomid Nezara viridula (L.) invade bean fields from alternative host-plants at the same time as H. armigera. This species, even in small numbers, causes the loss of young pods and also damages or kills the developing seed. It is not controlled by the standard DDT treatment for H. armigera, but the following insecticides were found to be effective: γBHC 20% e.c. (1¼ pt), dieldrin 18% e.c. (2 pt) and endosulfan 35% e.c. (1½ pt) in 2 gal spray/acre. Where N. viridula and H. armigera are found together, the standard recommendation is endosulfan 35% e.c. (1½ pt/2 gal spray/acre).The Coreids Acanthomia horrida (Germ.) and A. tomentosicollis (Stål) cause damage similar to that of N. viridula, but are serious only when infestations are heavy. They were found to be controlled by DDT, dieldrin or endosulfan at the rates given above.Alatae of the bean aphis Aphis fabae Scop, invade bean fields mainly during the first two weeks of the crop, producing apterae which concentrate on the tip of the plants. Damage (stunting, and loss of flowers and pods) is serious only when large populations of apterae are produced on a high proportion of the young plants. The early infestation demands control measures separate from those for the other pests, the most effective being methyl-demeton 50% e.c. (½ pt/2 gal spray/acre) applied 3–4 weeks after emergence. Endosulfan, although promising and far less toxic than methyl-demeton to larvae of the predator Cheilomenes lunata (F.), was discarded on grounds of cost, as was dimethoate. Aphid populations reached a peak during July and August and decreased with the warmer weather in September. A large number of alternative host-plants is listed, but the source of the primary flight into beans is not known.Melanagromyza phaseoli (Tryon), the life-cycle of which is completed in 23 days, is unimportant on seed beans as it is least abundant during the growing period of the main crop, but may damage plants suffering from water stress. Tunnelling in stems by larvae was controlled by seed dressings of aldrin or heptachlor (both 40% wettable powders mixed with seed at 1:200 w/w).

EXPERIMENTS AND OBSERVATIONS ON A VIRUS DISEASE OF WINTER SPINACH (SPIN ACIA OLERACEA)

SummaryA disease of winter spinach common in the Thames Valley has been shown to be of a virus nature. It is characterized by a mottling and malformation of the leaves, stunting of growth and death of the plants. The causal agent has been shown to be identical with cucumber mosaic I of Ainsworth.The disease is most prevalent in the earlier sown crops, and this appears to be correlated with their liability to be infested with aphides. Field observations on a number of farms indicated a correlation between intensity of aphis infestation and intensity of disease.Seed‐borne infection, though possible, has not been proved.Under field conditions in the Thames Valley it is suggested that a main source of contamination of winter spinach is the outdoor vegetable marrow crop.Postponement of date of sowing until the latter half of September is suggested as a method of reducing the amount of disease.