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Hy-Line W36® hens, 56-wk-old, were used to study the response to changing dietary Ca and P levels of hens laying eggs with heavy (HSW) or light shell weight (LSW). Three diets were fed: control diet [3.9% Ca and .55% total P (P t )], low-Ca diet (2.2% Ca and .55% P t ), and high-P diet (3.9% Ca and .90% P t ). In Experiment 2, one half of hens previously fed the low-Ca diet were changed to a Ca-deficient diet (1.7% Ca and .55% P t ), and the others continued to receive the diet previously fed. Also, one half of the hens fed the high-P diet were changed to a high-Ca, high-P diet (4.4% Ca and .90% P t ), and the others continued to receive the high-P diet. The control hens continued to receive the control diet. Shell weight was determined, and feed intake and egg production (EP) were recorded. Calcium and P intake, and Ca utilization were calculated. Plasma Ca and P, tibia breaking strength, and bone ash were determined.In both experiments egg production and shell weight were significantly lower for hens consuming both low-Ca and Ca-deficient diets than hens fed the control diet. The adverse effect was greater for HSW hens than for LSW hens. Many of HSW hens ceased production when fed the Ca-deficient diet. Calcium utilization was greater for HSW than for LSW hens. Increasing P in the diet from .55 to .90% P t had no significant effect on SW or EP. Increasing Ca in the diet from 3.9 to 4.4% and P from .55 to .90% P, had no significant effect on either EP, SW, or feed intake. Bone breaking strength and bone ash were not affected by dietary treatments. Plasma Ca and P concentrations were higher in the LSW than HSW hens. (

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Improving soil water holding capacity (WHC) through conservation agriculture (CA)-practices, i.e., minimum mechanical soil disturbance, crop diversification, and soil mulch cover/crop residue retention, could buffer soil resilience against climate change. CA-practices could increase soil organic carbon (SOC) and alter pore size distribution (PSD); thus, they could improve soil WHC. This paper aims to review to what extent CA-practices can influence soil WHC and water-availability through SOC build-up and the change of the PSD. In general, the sequestered SOC due to the adoption of CA does not translate into a significant increase in soil WHC, because the increase in SOC is limited to the top 5–10 cm, which limits the capacity of SOC to increase the WHC of the whole soil profile. The effect of CA-practices on PSD had a slight effect on soil WHC, because long-term adoption of CA-practices increases macro- and bio-porosity at the expense of the water-holding pores. However, a positive effect of CA-practices on water-saving and availability has been widely reported. Researchers attributed this positive effect to the increase in water infiltration and reduction in evaporation from the soil surface (due to mulching crop residue). In conclusion, the benefits of CA in the SOC and soil WHC requires considering the whole soil profile, not only the top soil layer. The positive effect of CA on water-saving is attributed to increasing water infiltration and reducing evaporation from the soil surface. CA-practices’ effects are more evident in arid and semi-arid regions; therefore, arable-lands in Sub-Sahara Africa, Australia, and South-Asia are expected to benefit more. This review enhances our understanding of the role of SOC and its quantitative effect in increasing water availability and soil resilience to climate change.

Water percolation and storage in a model sandy soil amended with four superabsorbent polymers (SAPs) was investigated using drip irrigation with two discharge rates. Superabsorbent polymers (Watersorb, Ag-SAP, Tera-Gel and Water-crystals) were mixed with the soil at three concentrations [0.2% or 0.4% (W/W) and control (0.0%)]. All soil columns received a fixed amount of water at two discharges i.e., 2.0 or 4.0 L h -1 . The percentages of percolated and retained water (relative to total water applied), gravimetric soil water content (G-wc) and bulk density (BD) were determined. All SAPs, at any concentration and water application rate, reduced the percentage of percolated water (PPW) and BD and increased the total soil porosity (TP). The reduction of PPW resulted in increases in soil water storage that were proptional to SAPs concentration. Under low water application rate, SAPs were more efficient as compared with high water application rate, because SAPs had enough time to reach their maximum water absorption capacity (WAC). At a SAPs concentration of 0.4% and low water application rate, Watersorb, Tera-gel and Ag-sap were acting equally and were best performing, as the G-wc increased by 2.6 folds compared to control. However, at the high water application rate, SAPs with higher water absorption rate "WAR" (Watersorb) worked best, as its particles swell faster. It can be concluded that, WAC of SAPs is important when irrigation water application rate is low and at high water application rate, WAR would be the most important property allowing SAPs to reach complete water absorption during short irrigation duration.