The recent use of heavy machinery combined with frequent disk tillage has created a subsurface compacted horizon in many of the irrigated soils of Morocco. The objective of this study was to evaluate the effect of subsurface compaction on the mot and shoot growth, grain yield, and grain yield components of wheat (Triticum aestivum L.). Field experiments were conducted in 1982 and 1983 on a Moroccan clay loam soil (typic Calcixerolls). Soil compaction was artificially created. The 0.10‐m surface layer was removed from all plots with a road scraper. The exposed subsurface layer was then packed by making four passes over the plots with a 7.5‐ton tractor. The removed soil was then replaced and leveled. Control plots were tilled with a disk plow followed by two passes of a disk harrow. Both compacted and control plots were then roto‐tilled for final seedbed preparation. The result of this compaction was a 12 to 23% decrease in grain yield and 9 to 20% decrease in straw yield. The decrease in yield was accompanied by a consistent reduction in the number of shoots per unit area. Number of kernels per spike and kernel weight were unaffected. Both root growth and distribution were markedly changed as a result of subsurface compaction. Wheat plants in compacted plots had a denser, finer, and shallower root system than wheat plants in control plots. Plant height, and leaf area and dry matter per shoot were also unaffected. The decrease in shoot number might be attributed to a limitation in the amount of available soil N to the roots.

Spatial characterization of crop residues and agrichemicals incorporated by tillage is needed to interpret biomass‐related soil processes. This study presents such a characterization. We first described oat residue (Avena sativa L.) and green‐sphere distributions produced by chisel plow (CP) and moldboard plow (MP) tillage and then described red‐sphere distributions when incorporated during secondary tillage. Finally the co‐location of incorporated oat residue and colored spheres was characterized. Green and red ceramic spheres were surrogates for shoot residue and incorporated agrichemical, respectively. Characterizations were derived from weights of soil and residue and counts of spheres in soil cores (1.84 cm diam. by 30 cm long, sectioned into 15 sublengths each 2 cm long). Penetration with MP was 25 cm, CP was 15 cm, and cultivator was 17 cm. The MP incorporated 67% of residue in the 10‐ to 20‐cm depth, while more that 90% of the incorporated residue in the CP was between 1 and 11 cm deep. Secondary tillage had negligible influence on these depth distributions. Green‐sphere distributions were related more closely to tool penetration than those of oat residue because root and shoot tissue were not distinguished. Fractional porosity of the 5.32‐cm3 volumes, adjusted to account for oat residue and sphere volumes, was increased ≈12% due to these materials. Many 5.32‐cm3 volumes contained no oat residue, whereas only a few volumes had concentrations ≥4 times the mean residue concentration. Although oat residue was incorporated with primary tillage, residue and herbicide surrogates were co‐located in 35% of the volumes, many of which contained large concentrations of residue. Exclusive use of either primary tillage with the same secondary tillage produces an environment for characteristically different bioactivity in the upper 10 cm.

Compaction in the 0.05-to 0.30-m depth may limit tillering and N accumulation in wheat (Triticum aestivum L.); these effects may be yield reducing. Before imposing compaction treatments in a field study in Minnesota, perforated small-diameter tubing was buried in a Waukegan silt loam (sandy skeletal, mixed, mesic Typic Hapludoll) at a depth of 0.2 m in all plots. Compacted plots each received four passes with a heavy vibrating roller, while control plots were disk plowed and then disk harrowed. All plots were then surface roto-tilled and seeded to wheat. At early tillering a K 15 N0 3 solution was applied to the subsurface via the tubing. Plants sampled for "N/N recovery 24 h after 15 N application, at anthesis, and at maturity showed no sig· nificantly different 15 N or N concentration or accumulation per culm/ individual organ in response to compaction. Because subsurface compaction reduced tillering, N uptake in the grain and straw was reduced by 21 and 30'fo, respectively. After the 0.10-m surface layer was re· moved from all plots in a field study on a clay loam soil (Typic Calcixerolls) in Morocco, the subsurface was compacted by four passes with a 7.5-ton tractor. Soil was then replaced, leveled, and only the control plots were disk plowed and disk harrowed twice. Both compacted and control plots were roto-tilled and seeded. Nitrogen concentration and accumulation per culm/individual organ immediately after tillering was reduced less than 5% by the compacted treatment M. Oussible,

Utilization of magnetically treated water has been investigated and applied in many countries such as Russia, Australia, Israel, China and Japan. Studies have shown that the magnetic field is used as a safe alternative to improve plant growth and development. Although the properties of magnetically treated water have received a great deal of interest in recent years, there are no studies conducted in Moroccan agricultural conditions. The present study aimed at gaining more insight on the effect of magnetically treated irrigation water (MTIW) in the northwest region of Morocco, on the yield of strawberry plants (Fragaria × ananassa Duch. cv. Camarosa) and its components. The experiments were conducted in situ, during two crop seasons (2011-2012 and 2013-2014). The results confirm that physical treatment of irrigation water by a static magnetic field improves the yield and quality of strawberry fruits. The percentages of increase in number of flowers, number of fruits, fruit yield and quality of export production per 100 plants were 27.4%, 30.9%, 34.8%, 24.3%, respectively, compared with normal irrigation water (average over both crop seasons). These results suggest that irrigation with MTIW improves the production as well as the quality of the strawberry fruit, thus water use efficiency was enhanced. Therefore, the MTIW can be considered as a promising technique for improvement but extensive research is still required.

Over the past three decades, soil compaction, especially of subsurface horizons, has become a serious problem in irrigated areas of Morocco. This study was designed to determine if subsurface compaction of a clay loam soil in Morocco could be effectively alleviated by subsoiling–to the extent that grain yields of wheat (Triticum aestivum L.) would be improved. A second objective was to document the nature of any resulting yield improvement in terms of changes in root and shoot growth, as well as in the standard components of grain yield. Field experiments were conducted in 1983 and 1984. A single‐tooth subsoiler was pulled through the soil at 0.4‐m intervals, to a depth of 0.7 m. Within the zone through which the tooth passed, soil bulk density was reduced by 11%, while soil porosity and air‐filled porosity were increased by 17 and 50%, respectively. Soil mechanical resistance of subsoiled plots was decreased by 19 to 33% at the 0.2‐ to 0.35‐m depth. At this same depth, roots were 54% longer per unit weight in subsoiled plots. Throughout the growing season, plants grown on subsoiled plots were consistently and significantly taller. These taller plants had more reproductive shoots, each with more and larger kernels. This resulted in an average yield increase of 48% for grain, and 28% for straw.