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A growth room pot experiment was conducted to relate differences in the aggregating ability of several grasses and legumes to root development and the frequency of VA mycorrhiza fungi. Forages with the most extensive root development within 80 d resulted in the greatest improvements in aggregation. Although the frequency of VA mycorrhiza varied between forages, it was not associated with improvements in aggregation. Key words: Soil structural deterioration, soil degradation, VA mycorrhiza, roots, grasses, legumes

Varying total amounts of water (160 and 320 mm) were infiltrated into 60-cm columns of air-dry saline sodic clay soil. The intervals between irrigation applications were varied from 5 to 20 days. The soil columns were subjected to a potential evaporation rate of 4.8 mm∙day−1 in a growth room. The cumulative evaporation followed a square root of time response, similar to that found by others for non-saline soils of coarser texture. An analytical solution of the Richards’ equation gave satisfactory (± 10%) prediction of cumulative evaporation at the end of the experiment as long as water was added in amounts of 40 mm or more per irrigation. The numerical solution to the Richards’ equation gave satisfactory estimates of evaporation for the latter stages of the experiment, but in the earlier stages it underestimated evaporation because of the too deep distribution of water in the soil given by this model. The neglect of hysteresis was invoked to explain the discrepancy between observed and predicted soil water content profiles. The "versatile soil moisture budget" empirical model also gave satisfactory prediction of evaporation but the successful prediction of water content profiles depended on "field capacity" values measured in situ. Key words: Soil moisture, modelling, water budgets, Richards’ equation

A study was conducted with five soil P tests (Bray P1 (1:10), Bray P1 (1:50), Mehlich II, Kelowna I and Kelowna II) to determine the effect of soil carbonates on postextraction pH and on the correlation between soil and plant P concentration. Alfalfa (Medicago sativa L.) was grown on five calcareous and six noncalcareous soils fertilized at 0 and 90 μg P mL−1 in a growth room experiment. The ability of the extradants to maintain a low pH with calcareous soils was poorest for the Bray P1 (1:10) followed by the Mehlich II, Kelowna I, Kelowna II and Bray P1 (1:50). The Bray P1 (1:10) did not give a statistically significant correlation coefficient between soil and plant P concentration with the calcareous soils, while the other methods did. Key words: Soil testing, calcareous soils, Bray P1, Mehlich II, Kelowna I, Kelowna II

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