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Crop rotations have evolved as a strategy to obtain harvestable yields in stressed environments due to improved water-use efficiency, nitrogen (N) fixation, and breaking diseases cycles. While fallowing or growing legume crops in the alternate year have shown to consistently increase yields in semi-arid environments such as in the Mediterranean area, little emphasis has been given to cereal quality in rotation trials, especially with respect to N, and thus improved animal and human nutrition. This paper reports the effect of those treatments on cereal quality parameters, especially N, and thus protein, in wheat grain and straw in a long-term (14 years) rainfed cropping systems trial in the medium rainfall zone (300–400 mm year−1) in northern Syria that examined seven alternative-year options with durum wheat (Triticum turgidum var durum), i.e., vetch (Vicia sativa), medic (Medicago spp.), chickpea (Cicer arietinum), lentil (Lens culinaris), fallow, watermelon (Citrullus vulgaris) as a summer crop in the fallow year, and continuous wheat. Two ancillary treatments involved N fertilization (0, 30, 60, 90 kg N ha−1) in the cereal phase, and stubble grazing management (moderate and heavy grazing, and no grazing or stubble retention). Both the rotation and N treatments had a significant influence on all parameters (test weight, grain and straw N percentage, and total N uptake). By comparison, grazing management had little influence on quality parameters except test weight; however, the residue × N interaction was significant. Rotations such as those with medic and vetch enriched the N in grain and straw. These rotations thus improved the nutritional value in terms of protein of the grain, an important consideration as per capita consumption of bread is high in the Middle East and other sources of protein are limited. Similarly, as grazed or fed straw is dominant in the diet of sheep, the enhanced nutrition is of significance. While fallow produced the highest yields, and is a hedge against the effects of drought, it produces grain and straw of low nutritional value with respect to protein, as a result of dilution of available soil N in the increased biomass. Though less obvious than yield, crop quality parameters should be considered in any cropping system involving rotations, especially those involving legumes.

Given the complex nature of rainfed cropping systems in Mediterranean agriculture and the dynamic nature of phosphorus (P) in soils, agronomic assessment of P fertilization must be long term in order to consider residual effects. Thus, a 9-year study involved initial relatively large applications of P (0, 50, 100, 150, 200 kg P2O5 ha-1) and yearly smaller dressings (0, 15, 30, 45, 60 kg P2O5 ha-1) in a trial involving dryland cereals (wheat/barley) in rotation with legumes (chickpea, lentil, or vetch) at three locations with varying mean annual rainfall in northern Syria; Breda (270 mm), Tel Hadya (342 mm) and Jindiress (470 mm). Assessment was made of grain, straw and total biomass yield and crop P uptake and available P (Olsen). While crop responses varied due to seasonal rainfall fluctuations, they tended to decrease with increasing initial available soil P levels (2.7, 6.2, and 4.4 mg kg-1 for Breda, Tel Hadya and Jindiress, respectively). Residual P was not significant for cereals or legumes at any site, but direct P was significant for both crops at Breda and Jindiress, as well as for legumes at Tel Hadya. In contrast, residual and direct P significantly influenced Olsen-P and seasonal and total P uptake. With no P fertilizer, or where minimal amounts (15 kg P2O5 ha-1) were applied annually, the balance between applied P and crop P offtake became increasingly negative; after 8 years without applied P, the P balance was -54, -38, -27, -17, and +7 kg ha-1 for the initial (residual) P application of 0, 50, 100, 150, and 200 kg P205, respectively. This was counterbalanced by the higher annual application rates and to a lesser extent the amounts of P applied initially. The study demonstrated the highly variable nature of crop responses to fertilizer P under semi-arid field conditions over several years, with soil moisture from seasonal rainfall being the dominant influence on overall yields. While crop responses may not occur in any given year, especially if available P is near or above critical threshold levels, dryland cropping without P fertilizer is unsustainable in the long run. © 2007 Elsevier B.V. All rights reserved.

Lentil (Lens culinaris Medikus subsp. culinaris) is traditionally grown as a rainfed crop globally, except in Sudan and Egypt, where it is grown under supplemental irrigation. Its seed is a rich source of protein for human consumption, and the straw is a valued animal feed in Near East. In the Mediterranean environment, lentil productivity is limited primarily by the amount and distribution of rainfall and temperature extremes. This study aimed to develop simple models to predict lentil seed and straw yields as a function of seasonal weather data (rainfall and temperature). Historical weather and yield trial data over 39 environments from three contrasting locations in Syria and Lebanon were used. Best-fit models for seed and straw yields in terms of climatic variables based on stepwise regression were developed. These accounted for over 77% variance in yield for both models. The overall responses to total seasonal rainfall were 5.16 kg ha−1 mm−1 seed yield and 10.7 kg ha−1 mm−1 for straw yield. Although May (period of pod-filling) rain contributed substantially to seed yield, high May temperatures reduced yield drastically. For straw yield, absolute minimum temperature and February temperature are important factors, in addition to total seasonal rainfall. The simple regression models developed from historical data not only describe the variation in lentil yields but can also be used for yield prediction purposes in the Near East.

While boron toxicity has been known for a long time, only recently has its widespread significance for field crops, especially barley ( Hordeum vulgare L. ssp. vulgare ), been recognized. Damage to crops is common in semi-arid areas where levels of hot-water-soluble (hws) B exceeds about 5 ppm. Frequently, much higher levels of B are found in the sub-soil than in the topsoil. This study examined the distribution of B in profiles from agricultural experiment stations across a mean annual rainfall gradient (196–471 mm/yr) in the semi-arid cereal-production zone in north–western Syria. A more intensive surface and depth-wise sampling was conducted at the driest barley-growing station, Boueidar, where plant toxicity symptoms were observed. The wetter stations had low levels of B throughout the profile, while the drier ones tended to have potentially toxic levels, which increased with profile depth. Only the Boueidar site had B accumulations within 20–40 cm of the surface. Profile sampling at Boueidar showed three distinct B distribution patterns, i.e., increasing with depth, uniform with depth, and a zone of B accumulation at 25–75 cm. Surface (0–20 cm) samples at Boueidar had spatially variable B concentrations. Leaching to remove excess B is impractical. Ideally, the problem may be tackled by exploiting genetic variation in B uptake. However, spatial and depth-wise variability shown in this study makes screening for B tolerance difficult in the field; as an alternative, B toxicity tolerance can be evaluated in the greenhouse. This work has heightened awareness of B toxicity in other countries of this agro–ecological zone.

Robustness of designs eliminating heterogeneity in two directions to outliers is studied. The important class of variance balanced row-column designs which satisfy the property of adjusted orthogonality are shown to be robust. Some general three-way balanced designs with balanced column vs row classification are also shown to be robust.