Evapotranspiration and water use of full and deficit irrigated cotton in the Mediterranean environment in northern Syria

Cotton (Gossypium hirsutum L.) is the most important industrial and summer cash crop in Syria and many other countries in the arid areas but there are concerns about future production levels, given the high water requirements and the decline in water availability. Most farmers in Syria aim to maximize yield per unit of land regardless of the quantity of water applied. Water losses can be reduced and water productivity (yield per unit of water consumed) improved by applying deficit irrigation, but this requires a better understanding of crop response to various levels of water stress. This paper presents results from a 3-year study (2004-2006) conducted in northern Syria to quantify cotton yield response to different levels of water and fertilizer. The experiment included four irrigation levels and three levels of nitrogen (N) fertilizer under drip irrigation. The overall mean cotton (lint plus seed, or lintseed) yield was 2502 kg ha-1, ranging from 1520 kg ha-1 under 40% irrigation to 3460 kg ha-1 under 100% irrigation. Mean water productivity (WPET) was 0.36 kg lintseed per m3 of crop actual evapotranspiration (ETc), ranging from 0.32 kg m-3 under 40% irrigation to 0.39 kg m-3 under the 100% treatment. Results suggest that deficit irrigation does not improve biological water productivity of drip-irrigated cotton. Water and fertilizer levels (especially the former) have significant effects on yield, crop growth and WPET. Water, but not N level, has a highly significant effect on crop ETc. The study provides production functions relating cotton yield to ETc as well as soil water content at planting. These functions are useful for irrigation optimization and for forecasting the impact of water rationing and drought on regional water budgets and agricultural economies. The WPET values obtained in this study compare well with those reported from the southwestern USA, Argentina and other developed cotton producing regions. Most importantly, these WPET values are double the current values in Syria, suggesting that improved irrigation water and system management can improve WPET, and thus enhance conservation and sustainability in this water-scarce region.Drip irrigation Production functions Water productivity Nitrogen application

In-season wheat root growth and soil water extraction in the Mediterranean environment of northern Syria

Wheat is the most important cereal crop in the semi-arid eastern Mediterranean region that includes northern Syria. Knowledge of wheat root depth and the vertical distribution during the winter growing season is needed for sound scheduling of irrigation and efficient use of water. This article reports evaluation of root development for three winter-grown bread (Triticum aestivum L.) and durum (Triticum turgidum L.) wheat under four soil water regimes (rainfed and full irrigation with two intermediate levels of 33 and 66% of full irrigation). Roots were sampled by soil coring to a depth of 0.75 m at four occasions during 2005-2006 growing season. Two distinct phases of root development were identified, a rapid downward penetration from emergence to end tillering phase, followed by a substantial root mass growth along the profile from tillering to mid-stem-elongation phase. Roots were detected as deep as 0.75 m during the initial rapid penetration, yet only 29% of the total seasonal root mass was developed. This downward penetration rate averaged 7 mm d-1 and produced 10.8 kg ha-1 d-1 of root dry-biomass. The bulging of root mass from tillering to mid-stem-elongation coincided with vigorous shoot growth, doubling root dry-biomass at a rate of 52 kg ha-1 d-1, compared to the seasonal root growth rate of 18.3 kg ha-1 d-1. A second-degree equation described the total root dry-biomass as a function of days after emergence (r2 = 0.85), whereas a simpler equation predicted it as a function of cumulative growing degree days (r2 = 0.85). The final grain yield was a strong function of irrigation regimes, varying from 3.0 to 6.5 t ha-1, but showed no correlation with root biomass which remained similar as soil water regimes changed. This observation must be viewed with care as it lacks statistical evidence. Results showed 90% of root mass at first irrigation (15 April) confined in the top 0.60-0.75 m soil in bread wheat. Presence of shallow restricting soil layers limited root depth of durum wheat to 0.45 m, yet total seasonal root mass and grain yield were comparable with non-restricted bread wheat. Most root growth occurred during the cool rainy season and prior to the late irrigation season. The root sampling is short of rigorous, but results complement the limited field data in literature collectively suggesting that irrigation following the rainy season may best be scheduled assuming a well developed root zone as deep as the effective soil depth within the top meter of soil.

A field test of Root Zone Water Quality Model - pesticide and bromide behavior

The Root Zone Water Quality Model is a process-based model that integrates physical, chemical and biological processes to simulate the fate and movement of water and agrochemicals over and through the root zone at a representative point in a field with various management practices. The model was evaluated with field data for the movement of water and bromide, and the transformation and transport of cyanazine and metribuzin in the soil profile. The model reasonably simulated soil water and bromide movement. Pesticide persistence was predicted reasonably well with a two-site sorption model that assumes a rate-limited adsorption-desorption process with the additional assumption of negligible degradation of interaggregate-adsorbed pesticides

PROSTATEx Challenges for computerized classification of prostate lesions from multiparametric magnetic resonance images

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Genome-wide association mapping for isolate-specific resistance to Ascochyta rabiei in chickpea (Cicer arietinum L.)

Ascochyta blight caused by Ascochyta rabiei is one of the most important foliar diseases of chickpea that can lead to significant yield losses worldwide. A genome-wide association study (GWAS) was applied on a panel of 165 chickpea genotypes against A. rabiei isolates belonging to six different pathotypes. Large phenotypic variation in disease reaction was observed, as the frequency of resistance to pathotypes-I and III was comparatively higher than resistance to other pathotypes. Overall, among the all genotype × pathotype interactions, 259 resistance responses were identified and genotypes were grouped into four clusters based on their phenotypic reactions. The chickpea panel genotyped using DArTseq assay was used for genome-wide association mapping (GWAS). The GWAS revealed 30 marker-trait associations (MTAs) representing 17 quantitate trait loci (QTL) across all chickpea chromosomes. Among them, 11 R-QTLs were associated with resistance to specific pathotype, and 6 R-QTLs were associated with resistance to two or more pathotypes. Most of these R-QTLs overlapped with the previously reported R-QTLs for resistance to A. rabiei, whereas identified R-QTLs on chromosomes Ca1, Ca2, Ca6 and Ca7 are most likely novel. Meanwhile, annotation within the R-QTL intervals revealed genes involved in salicylic acid (SA) and jasmonic acid (JA) regulation pathways as well as cell death programming. The known and novel R-QTL identified in this study may be targeted for use in future chickpea breeding programs to recombine different loci to improve the durability of resistance to multiple A. rabiei isolates/pathotypes