Bryant R. Gardner

Midrib nitrate concentration as a means for determining nitrogen needs of cauliflower

Abstract Plant analysis has been used to evaluate the nutritional status of many crops for diagnostic and corrective purposes. This study was initiated to establish critical nitrogen (N) plant tissue levels using midrib NO3‐N concentration for cabbage (Brassica oleracea L., capitata group) during the growing season. Tissue samples for nitrate analysis were taken from cabbage plants over a period of four growing seasons beginning at the 4 to 6 leaf stage of growth and biweekly through pre‐harvest. The midrib from the most recently full sized leaf was sampled for NO3‐N concentration determination. A high degree of correlation existed between NO3‐N concentration in cabbage midribs at various sampling dates and yield as determined by stepwise regression analysis. Nitrate‐N concentration in cabbage midribs indicated the N status of the plant. Minimum or critical levels of NO3‐N in cabbage midribs for sampling dates throughout the growing season were established for conditions such as are found in the desert re...

Growth and yield of mature 'Valencia' oranges converted to pressurized irrigation systems

A study was conducted during four seasons to evaluate the performance of mature ‘Valencia’ orange trees converted to pressurized irrigation systems. Trees irrigated by trickle, bubbler, spray, and sprinkler systems were compared to trees irrigated by the traditional border-flood irrigation method used in the southwestern Arizona desert region. During the first year only trees irrigated by the sprinkler system grew significantly less than trees irrigated by border-flood. During the second year after conversion, trees irrigated by border-flood grew significantly more than trees irrigated by any of the pressurized systems. However, there were no differences in tree growth during the third and fourth years, suggesting that the trees adapted to the new irrigation systems. Effects of irrigation treatments on leaf concentrations of N, P, Fe, Zn, Mn, and Cu were minimal. There were significant differences in orange yields from trees among the different irrigation treatments within years. However, average or total tree yields over the four-year period did not vary due to irrigation treatment. Similarly, there were no consistent differences in fruit or juice quality. Overall, results from this study indicate that mature ‘Valencia’ orange trees can be converted to pressurized irrigation systems with minimal effects on fruit yield and quality. Under the conditions imposed in the studies, 33% less irrigation water was utilized with the pressurized systems compared to border-flood.

Modified self-moving irrigation system for water-nitrogen crop production studies

A lateral move irrigation system was modified so that controlled quantities of water and nitrogen could be applied to field plots. The system was designed to be mobile so that it could irrigate crops in several fields that were grown using different cultural management practices. The system design can be extended from studies of irrigation scheduling to varying the depth of water applied. The number of spray lines could be increased or the nozzle arrangement varied to give different treatment effects. A technique was developed to verify the system flow rate and nitrogen injection rate using a nitrate specific ion electrode. A central composite rotatable statistical design was used to reduce the number of plots required without reducing the plot size to obtain meaningful data and minimize experimental resources. Data collected from these plots can be used to predict water-nitrogen response surfaces of the quadratic form.

Asparagus spear size distribution and earliness as affected by water and nitrogen applications.

ABSTRACT Green asparagus production is affected by water and nitrogen applications, and soil and air temperatures. Reduced water and nitrogen applications lowered the total yield for the 60-day harvest. Nitrogen deficiencies, to a greater extent, reduced the number of spears produced than did lower water application levels. Average spear weight was increased with optimum applications of water and nitrogen. Low water applications changed the spear size distribution which resulted in the production of smaller spears compared to treatments receiving greater amounts of water. Low nitrogen levels also changed the spear size distribution compared to optimum or greater nitrogen levels and also reduced the total yield for all harvest periods. Asparagus production early in the harvest season (0-20 days) was reduced for low nitrogen treatments when soil temperature was lowest. The rates of production were constant for all water and nitrogen treatments from day 20 through day 60. All asparagus size classes showed an increase in yield for the first 30 harvest days. After 30 days the production of larger spears decreased for each successive harvest interval, while the production of smaller spears remained constant, and then showed a large increase during the last harvest interval.

Asparagus Yield Response to Water and Nitrogen

ABSTRACT FRESH green asparagus {Asparagus officinalis L.) is produced in the Southwest desert regions during a period when it cannot be produced in colder areas. The success of producing optimum yields economically is dependent on the proper applications of water and nitrogen. All water requirements must be met by irrigation since less than 75 mm (3 in.) of annual rainfall occurs in this region. Nitrogen is a critical nutrient that must be applied to obtain maximum yields. Maximum yields of 11.6, 18.6, and 10.0 Mg/ha(9700, 16,700, and 8900 Ib/ac) were predicted for asparagus crowns that were 3, 4 and 5 years old, respectively. The amount of water applied to obtain these yields ranged from 270 to 310 cm (106 to 122 in.) and the amount of nitrogen fertilizer applied ranged from 370 to 630 kg/ha (330 to 560 Ib/ac). Production functions were developed to predict asparagus yields for water applications that ranged from 50 to 150% of the estimated evapotranspiration and nitrogen applications that ranged from 33 to 167% of the recommended nitrogen rate. A generalized prediction equation was calculated by normalizing the yield, and the amounts of water and nitrogen applied. A total seasonal water depletion rate of 2500 mm (98 in.) was calculated for the fern growing season. Water applications at this level would result in a relative yield of 0.98. Maximum soil water depletion rate of 14 mm (0.55 in.)/day was measured during the fern growing season from late June through early August. An average soil water depletion rate of 0.4 mm (0.01 in.)/day was measured during the harvest season. Irrigations may not be required during the harvest season to replenish soil moisture but may be required for other cultura practices.

Determining phosphorus needs for cabbage grown on calcareous soils

Abstract Cabbage (Brassica olearacea var. capitata L.) yield differences from added P were highly significant up to the predicted response level of 0.4 mg 1 . The increases in yield were basically due to larger head sizes. No statistical differences were found after the soil P levels were adjusted above 0.4 ppm, as determined by P isotherms constructed from initial soil samples. Slight differences occurred between years, but likely were due to cultivar growth differences. Data show that the isotherm predicted level fits rather closely the P requirements for cabbage as related to crop yields. Since extraction methods measure only the intensity factor of P, these methods could lead to incorrect P fertilization recommendations. The absorption of P is progressively reduced as the temperature goes down.