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Accueil du site → Master → Etats Unis → 1987 → On-farm evaluation of wheat production as affected by three weeding systems and top-dressed nitrogen in Chaouia (semi-arid zone of Morocco)

Kansas State University (1987)

On-farm evaluation of wheat production as affected by three weeding systems and top-dressed nitrogen in Chaouia (semi-arid zone of Morocco)

Tanji, Abbes

Titre : On-farm evaluation of wheat production as affected by three weeding systems and top-dressed nitrogen in Chaouia (semi-arid zone of Morocco)

Auteur : Tanji, Abbes.

Université de soutenance : Kansas State University

Grade : Master of Science (MS) 1987

Résumé
In dryland farming areas of Morocco, little critical attention has been given to weeds associated with wheat ; whereas, insect pests and plant diseases have drawn much greater attention of the farmers and researchers. There are three approaches to weed control in wheat in the Chaouia : 1) no control whatsoever, 2) manual removal of the largest, most conspicuous weeds, which are usually, but not always collected for use as forage, and 3) chemical control using phenoxy-type herbicides applied at the ful-tiller growth stage of wheat.
Nitrogen fertilizer is often added at planting time, and the crop may be top-dressed with additional nitrogen if winter rainfall is favor able. The purpose of this research was to study the above three weed ing systems on farms in a part of the Chaouia (semi -arid) region, to determine possible effects of top-dresssed nitrogen on the weeding systems, and to characterize the weed flora of these wheat fields. Forty (40) identical experiments were established in bread wheat ( Triticum aesti v u m L.) and durum wheat ( Triticum durum Desf .) at the early-tiller stage during 1984-1985 and 1985-1986 growing seasons. Most of the experimental sites had been broadcast seeded. Top-dressed nitrogen (25 kg/ha) applied at early-tiller stage had no significant effect on wheat grain yield. Fertilization at seeding or from previous crops provided enough nitrogen so that there was no advantage from additional top-dressed nitrogen.
For the two years, weed numbers were reduced an average of 30% by hand-weeding. Treatment with 2,4-D removed 66% of the weeds in 1985 1986. Hand-weeding removed an average of 63% of the weed dry weight in the two years. Treatment with 2,4-D reduced weed dry weight by 82% in 1985-1986. Hand -weeding for forage produced an average of 570 kg/ha weed dry matter in 1984-1985, and 284 kg/ha in 1985-1986. However, it lowered wheat grain yield by 231 kg/ha in 1984-1985, and 127 kg/ha in 1985 1986. Over both years, the cost of each kg weed forage was 0.43 kg grain yield loss. Nonweeding reduced grain yields by 158 kg/ha in 1984-1985 and 101 kg/ha in 1985-1986, compared to 2,4-D treatment. Weed control with 2,4-D increased wheat grain yields over both nonweeded and hand-weeded treatments by an average of 154 kg/ha, over both seasons.
A total of 157 weed species belonging to 29 botanical families were identified on all 40 experimental sites in both years ; 89% were dicots. Corn poppy ( Papaver rhoeas L.), a 2,4-D susceptible plant, was the most abundant annual weed in wheat fields in Chaouia. Subsequent studies could investigate the timing and density thresh old of weeds in wheat, as well as the economic and social advantages and disadvantages of each weeding system.

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