Reuben B. Beverly

DRIS diagnoses of soybean nitrogen, phosphorus, and potassium status are unsatisfactory

Abstract Previous research has shown that the Diagnosis and Recommendation Integrated System (DRIS) is useful to identify the nutrient most likely to limit yield of soybean (Glycine max). However, recent work with other crops has shown that DRIS diagnoses are sometimes unsatisfactory due to large numbers of false positve (F+) diagnoses, which would lead to recommendation of unnecessary fertilizer application. This paper reports a reconsideration using the prescient diagnostic analysis approach of data previously used to establish the diagnostic utility of DRIS for soybean. In addition to previously‐published evaluation criteria, the approach is extended by defining an efficiency rating which accounts for differences in the incidence of sufficient and deficient cases. Using this evaluation approach, DRIS phosphorus (P) and potassium (K) diagnoses of soybean using numerous sources of norms and methods to calculate function values and nutrient indices led to unacceptable efficiency ratings (<67%), even thoug...

Video image analysis as a nondestructive measure of plant vigor for precision agriculture

Abstract Precision agriculture addresses spatial variability across a field in order to optimize application of fertilizer and other inputs on a site‐specific basis. Soil testing provides predictive information on patterns in soil fertility and other soil conditions, but plant vigor provides a more direct and integrative indication of plant response to soil properties and management. Spatial patterns in plant vigor also provide greater resolution of soil effects than is practical using soil testing. This paper describes recent experience in applying video image analysis in monitoring plant growth (i.e., percent ground cover) as an index of vigor in field situations. Using off‐the‐shelf technology, video images are recorded, digitized using an image capture computer board, then measured for percent ground cover using image analysis software. Results demonstrate that video image analysis is rapid and economical and can be used to detect patterns to guide subsequent soil sampling and mapping.

Re‐evaluation reveals weaknesses of DRIS and sufficiency range diagnoses for wheat, corn, and alfalfa

Abstract In prescient diagnostic analysis, conclusions about the need for fertilizer application based upon nutrient diagnostic methods are compared to independently‐determined correct diagnoses based upon yield responses to nutrient application. If a nutrient is diagnosed as being required (i.e., deficient or insufficient), the diagnosis is positive; no requirement is a negative diagnosis. Diagnoses are verified and classified as either true or false by their agreement with observed presence or absence of significant yield increases in response to application of the nutrient in question, A diagnostic method is considered acceptable only if: 1) at least 50% of all verifiable diagnoses are correct; 2) positive diagnoses are true more often than false; and 3) the net yield effect attributable to indicated nutrient treatments is positive. Using this approach, previously published Diagnosis and Recommendation Integrated System (DRIS) and published or derived concentration‐based diagnoses of wheat, corn and al...

Nitrogen, phosphorus, and potassium effects on pre‐ and post‐transplant growth of salvia and vinca seedlings

Abstract Pre‐ and post‐transplant growth of bedding plants is affected by seedling nutrition. However, there is little information available on how seedling nutrition affects the growth of ornamental bedding plants. In this study, we quantified the effects of nitrogen (N) (8 to 32 mM) and phosphorus (P) and potassium (K) concentration (0.25 to 1 mM) of the seedling fertilizer on pre‐ and post‐transplant growth and nutrient element content of salvia (Salvia splendens F. Sellow ex Roem. & Schult.) and vinca (Catharanthus roseus L.) seedlings. Shoot growth of salvia and vinca increased with increasing concentrations of N in the pre‐transplant fertilizer and these differences lasted until the end of the study at 15 days after transplanting. Pre‐transplant root dry mass of these species was not affected by the N concentration of the fertilizer, but root dry mass at 12 days after transplanting was positively correlated with the N concentration of the pre‐transplant fertilizer. Increasing N concentrations in the...

Calibration of a video image analysis system for measurement of stem length, leaf area, and percent ground coverage

Abstract A relatively low‐cost digital measurement system configured with off‐the shelf components (a standard consumer High 8‐mm camcorder, video cassette recorder, video monitor, desktop computer with image capture board, and image analysis software) has been used in applications from benchtop stem length and leaf area measurements to aerial imaging for precision agriculture applications. However, preliminary research identified a systematic error in estimating leaf area using this system, which further investigation revealed to be caused by the internal calibration method used. Further research was needed to determine appropriate calibration methods for length and area measurements using this system. Length measurements were very accurate and repeatable using a vertical (i.e., parallel to the axis of objects) two‐point calibration. Two‐point (vertical, horizontal or diagonal) calibration led to over‐ or under‐estimation of area, but three‐point calibration yielded very accurate measurements of area and...

NEITHER BLOOM PERIOD NOR POSTBLOOM NITROGEN APPLICATION REDUCES COLD HARDINESS IN CRAPEMYRTLE

In a 2-year field study, 5-year-old field-grown ‘Natchez’ crapemyrtles were either not fertilized with nitrogen (N), or received 100 kg N/ha (89 lbs N/acre) as urea-ammonium nitrate solution applied in six biweekly applications either mid-June through early August (bloom stage) or late August through late October (post bloom). Treatments had virtually no effect on the development or degree of cold hardiness attained as measured by lowest survival temperature on twig samples collected monthly from November to March. Nitrogen application increased leaf N concentration in 1994, but not in 1995. Nitrogen fertilization reduced leaf phosphorus (P) concentrations both years, presumably due to the dilution effect, but only reduced the leaf potassium (K) concentration in August 1994. Nitrogen treatments increased stem diameter 4% compared to the control, but sidedress timing had no effect.

Modification of the M‐DRIS for soybean

Abstract Previous research shows that the diagnosis and recommendation integrated system (DRIS) and modified‐DRIS (M‐DRIS) have inherently biased data base means and CVs that affect the accuracy of nutrient diagnoses. Our objective was to remove these biases and determine their effect on phosphorus (P) and potassium (K) diagnoses for soybean (Glycine max L.). Four sets of soybean M‐DRIS nutrient norms (linear, L; log‐transformed, LT; corrected anti‐log, CAL; and corrected anti‐log population, CALP) were derived for use in evaluating P and K deficiencies and sufficiencies. The four data bases differed in that: (i) the L, LT, and CAL norms were developed from 639 soybean leaf samples yielding in excess of 3500 kg/ha, while those for CALP were calculated from 3898 samples from all available yield levels, (ii) L norms were calculated from non‐log‐transformed nutrient data, while LT, CAL, and CALP norms were calculated from log‐transformed data, and (iii) CAL and CALP concentration means were developed by tak...

Evaluation of the moisture equivalent soil test for irrigation management

Abstract Previous research demonstrated that the moisture equivalent (ME) soil test measured at about ‐80 kPa reflects soil clay and organic matter contents, exhibits good precision, and is well correlated to the ‐33 kPa pressure plate estimate of field capacity. However, data to guide interpretation of the ME results in irrigation management are lacking. In the present research, soil mixes comprising 45 to 100% sand, 0 to 50% clay, and 0 to 5% peat by volume were used to determine the effects of soil composition on ME measured at either ‐13 or ‐80 kpa. The plant available water capacity (AWC) was determined by growing plants in pots containing the soil mixes. Volumetric ME measurements at either ‐13 or ‐80 kPa increased linearly with clay content, as did the volumetric water content at wilting point (WP). Hence, the estimated AWC was essentially constant across the entire range tested. If WP and AWC estimates from this greenhouse study reflect field conditions, the results do not support soil testing to ...

Moisture equivalent as a routine soil physical test to guide irrigation management

Abstract Although water retention and movement in soils determine both the need for irrigation and the loss of nitrogen (N) from agricultural systems, soil physical tests are generally too time‐consuming for routine analysis by soil testing laboratories. We evaluated the potential of the Moisture Equivalent (ME) method as described by Bouyoucos for routine soil physical measurement. The method consists of saturating a sieved soil sample in a Buchner funnel, vacuum filtering the sample for 15 min while covered, then determining the gravimetric water content. On 72 soil samples run in triplicate, ME results were highly repeatable (CV values generally less than 3%). In addition, ME results were linearly correlated to clay and organic matter contents (R2 = 0.85) and to 33 kPa moisture content (R2 = 0.85). We conclude that the ME method is sufficiently convenient to run routinely in a soil testing laboratory, and sufficiently dependable to improve precision in irrigation and N management. Interpretive criteria...

Soybean seed yield and nutrient diagnoses as related to plant nutrient balance

Abstract Both nutrient concentrations and nutrient ratios of plants have been associated with crop seed yields, but research examining their relative correlation to yield is scarce. Furthermore, research comparing nutrient diagnoses by the modified‐diagnosis and recommendation integrated system (M‐DRIS) against diagnoses resulting from use of M‐DRIS concentration means as critical nutrient levels (CNLs) is lacking. Consequently, a soybean [Glycine max (L.) Merrill] cultivar by phosphorus (P) by potassium (K) by limestone soil fertility field study conducted on a Cresco loam (fine‐loamy mixed, mesic Typic Argiudoll) was used to determine: (i) whether plant nutrient concentrations or ratios better accounted for differences in soybean seed yield; and (ii) whether diagnostic systems that use nutrient concentrations or nutrient balance are more accurate in diagnosing soybean P and K status. Correlation analyses demonstrated that both nutrient concentrations and nutrient ratios were related to yield, but parti...