This item was digitized as part of the Million Books Project led by Carnegie Mellon University and supported by grants from the National Science Foundation (NSF). Cornell University coordinated the participation of land-grant and agricultural libraries in providing historical agricultural information for the digitization project; the University of Arizona Libraries, the College of Agriculture and Life Sciences, and the Office of Arid Lands Studies collaborated in the selection and provision of material for the digitization project.

This item was digitized as part of the Million Books Project led by Carnegie Mellon University and supported by grants from the National Science Foundation (NSF). Cornell University coordinated the participation of land-grant and agricultural libraries in providing historical agricultural information for the digitization project; the University of Arizona Libraries, the College of Agriculture and Life Sciences, and the Office of Arid Lands Studies collaborated in the selection and provision of material for the digitization project.

No description available.

Comparisons between subsurface trickle-(drip) and furrow-irrigated leaf lettuce, scheduled by AZSCHED and by tensiometers were made to evaluate their effects on crop coefficient, crop water use, nitrogen uptake and nitrogen leaching. A field experiment with four treatments and five replications was conducted during the fall-winter 1994-95 growing season at The University of Arizona's Campus Agricultural Center. Results showed that there was no significant difference at 95% confidence level among treatments, with respect to crop coefficients. A Fourier series was fitted to represent the Growing Degree Days (GDD)--Crop coefficient (Kc) relationship that can be recommended for irrigation scheduling of leaf lettuce at any geographical situation and planting date. A table of Kc for "days after thinning" was derived for Tucson-AZ. Marketable yield averaged 25.0 Mg ha⁻¹ with crop water use efficiency of 9.8 Kg of marketable yield per cubic meter of water (including rainfall). The 1994-95 growing season was not typical for Tucson-AZ. There was 181 mm of rainfall compared to the long term average of 91 mm. Based on the studied condition we could also conclude that, for supplementary irrigation, that is typical of humid areas, there is no difference if one irrigate leaf lettuce by short-end-closed furrow or subsurface - trickle irrigation, scheduled either by tension of 20 kPa or AZSCHED software, concerning yield and nitrogen uptake. The risk of nitrogen leaching is higher for furrow irrigation systems than for drip.

Tepary beans perform better than common beans under drought conditions. The mechanism of drought tolerance in tepary bean seedlings was explored by determining the water potential, osmotic potentia4 relative water content and level of free sugars and concentration of K ions within expanding leaves. Two week old seedlings were subjected to a gradual water stress with sorbitol solutions exhibiting OP values of -0.19 MPa and -0.47 MPa. Tugor remained constant whereas WP, OP and RWC declined following the stress treatment. Osmotic adjustment (0.4) occurred in each treatment but the contribution of sucrose and fructose to OA was minor. Some sorbitol was translocated to leaves and contributed to OA. The K ions did not contribute to the OA. A significant decrease in cell size was observed

The objectives of this research were i) to observe the movement of the wetting front in subsurface drip irrigated lettuce and broccoli, 2) to analyze variability in soil water tension (SWT) within the profile, and 3) to determine root distributions of subsurface drip irrigated lettuce and broccoli. Lettuce and broccoli plots at the Maricopa Agricultural Center during the 1992-93 and 1993-94 winter growing seasons were intensively instrumented with automated tensiometers. During both seasons, there was good agreement between mean daily SWT, and SWT measured before irrigation. During 1992-93, the maximum variation in mean SWT among tensiometers was 2.5 kPa. Among tensiometers within the zone of greatest root density, the maximum variation was only 1.5 kPa. Therefore, the range of SWT within the lettuce root zone was small, and tensiometer placement anywhere within the root zone would have been adequate. During 1993-94, the maximum variation in mean SWT among tensiometers was 7 kPa. The maximum variation among tensiometers within the zone of greatest root density was 5.3 kPa. The larger variation in mean SWT among tensiometers, compared to lettuce, is due to the greater water use of broccoli. Tensiometer placement will be more critical for higher water use crops. During both seasons roots proliferated around the drip tubing. These results substantiate the assumption that tensiometer placement anywhere within the zone of greatest root density will be adequate for irrigation scheduling of subsurface drip irrigated crops.

The objective of this research was to estimate a season -long water balance under one subsurface trickle- irrigated plot each of lettuce (Lactuca sativa L. var. Waldmann's Green) and broccoli (Brassica olearacea L. var. Claudia). One lettuce plot during 1992-93 and one broccoli plot during 1993-94 were intensively instrumented with automated tensiometers. Tensiometer readings and estimates of evapotranspiration were used to estimate seasonal water contents in the crop root zone, and water losses due to leaching. For the monitored portion of the 1992-3 growing season, 19.1 an of irrigation water was applied, 12.5 cm of rainfall fell, and ET, was 11.5 cm. Estimated deep percolation was 60% of total water applied (irrigation plus rainfall). Leaching was periodic, and was mostly associated with rainfall events. During the monitored portion of the 19934 season, 21.2 cm of irrigation water were applied, 8.0 an of rainfall fell, and ET, was 21.9 cm. Estimated deep percolation was 28% of total water applied. Almost all of this leaching was associated with one major rainfall event. Water stored in the root zone (top 50 cm) was relatively constant at 12-14 cm water/50 cm soil except after rainfall.

This study occurred at the Ventilla Ecologic farm, situated in the central Altiplano of the Murillo province, 26 km from La Paz. Its objectives were to evaluate two types of irrigation, by drip and by microasperation, in spinach and Swiss lettuce in Walipinis, and to conduct an economic analysis. The genetic material used was spinach (viroflay variety) and Swiss lettuce (large-leaved variety). Chapin irrigation belts and nebulizers were used, and two tensiometers were used to determine the soil moisture. Manual planting occurred on September 1, 2002, in all experimental areas. Seeds were dispersed in a continual flow with Swiss lettuce at a density of 3.5g/m2 and three bobbins, and in spinach the density was 0.26 g/m2 in parallel, 20 cm rows with the irrigation belts on either side. The spinach harvest was spread out, while the Swiss lettuce harvest occurred all at once. A factorial arrangement was used in this study, with two factors: two levels of irrigation (drip and microasperation) and different crops (spinach and Swiss lettuce). The response variables regarding drip irrigation efficiency had a uniformity coefficient of 97%, and microasperation had 85%. The depth reached by the watered bulb after two hours of control was more than 20 cm, while the microasperation only reached 15 cm after two hours. Irrigation occurred at midday but in accordance with the readings that the tensiometers gave. The response variables studied in the crop were: percentage germination, number of leaves, plant size, leaf size, and yield. Yield showed significant differences between types of irrigation of crops. Drip irrigation was better than microasperation. The response variables that had the greatest effect on yield were number of leaves, plant size, and leaf size. The economic production analysis found negative net benefits for the first trial. In the second trial, drip irrigation netted Bs.3.54/m2 for spinach and Bs. 3.68/m2 for Swiss lettuce, recovering the investment from the first trial. In contrast, the yield from microasperation irrigation, even though the second trial had positive net results, did not recover the investment from the first trial. Finally, based on these data, drip irrigation is recommended because of its better yields and a lower installation cost.