Agronomy Journal

Pearson, Calvin H.; Ernst, Susan M.; Barbarick, Ken A.; Hatfield, Jerry L.; Peterson, Gary A.; Buxton, Dwayne R.

doi: 10.2134/agronj2006.0312cpmid: N/A

During 2008 we celebrate the centennial anniversary of Agronomy Journal Many people have certainly been influenced in some way by the science published during the 100‐yr existence of the journal. From Volume 1 up through Volume 98 (2006) there have been more than 30,290 authors who published 15,232 articles totaling 89,056 pages. More than 2545 editors were required to review and edit the papers published in Agronomy Journal, in addition to the manuscripts submitted but not published. As a current snapshot of Agronomy Journal, we published 60% of the manuscripts submitted in 2005. In both 2003 and 2004, we accepted 55% of the manuscripts submitted. In a comparison of 48 peer journals in 2005, the impact factor of Agronomy journal ranked 12th at 1.473 and the total citations for the journal ranked fourth at 6723. Commentaries on the early history of Agronomy Journal have been previously published. In our article, we focus on the journal's history during the past 25 yr. We fully expect that the future of Agronomy Journal will be even more exciting, rewarding, challenging, and valued as the past 100 yr. We eagerly look forward to the next 100 yr of Agronomy Journal.

Damania, Adi B.

doi: 10.2134/agronj2005.0239cpmid: N/A

This paper has been written to look back at the early period of crop genetic resources conservation and inform readers of what has been achieved so far and what needs to be done in the future. The recognition of the value of crop genetic resources and early efforts at collecting germplasm by pioneer plant explorers, such as F.N. Meyer and N.I. Vavilov, and some of the strategies they employed are described. Historic examples of collection, evaluation, and utilization of genetic resources, notably by the late J.R. Harlan and other U.S. agronomists, are highlighted. The use of wild progenitors in improving biotic and abiotic stress tolerance has been covered. Previous and present status of genetic resources collection and storage, both ex situ in gene banks and in situ in the natural habitats of crops and their wild progenitors, is discussed. The creation of agrobiodiversity is a dynamic process and hence the work on conservation of genetic resources has to continue. With the increasing use of biotechnology in crop improvement, the value of germplasm already collected and conserved will substantially increase as researchers seek out new sources of useful genes in the future.

Miller, Fred P.

doi: 10.2134/agronj2007.0013pmid: N/A

The evolution of agriculture within the last 11,000 yr marked the first major inflection point in food yield and changed forever the character of the human condition. The application of technology to agriculture early in the 20th Century induced the next major crop yield inflexion point. Identifying the technological wellspring from which increased rates of productivity will be obtained in the decades ahead is far less obvious than during the last century. The agronomic challenge for the decades to come is to increase productivity per unit of land enough to preclude appropriation of other ecosystems for cropland expansions while simultaneously increasing the efficiency of production inputs, reducing their leakage to the environment, and sustaining the integrity of those ecological processes that undergird these intense biological production systems. Such a goal will require different metrics to measure agricultural sustainability and garner public support, new funding sources, and more holistic institutional arrangements. Agronomists, while playing a major role in meeting this challenge, will not necessarily dominate the agenda.

Mills, Cory I.; Bednarz, Craig W.; Ritchie, Glen L.; Whitaker, Jared R.

doi: 10.2134/agronj2006.0299pmid: N/A

New transgenic cotton (Gossypium hirsutum L.) technologies Bollgard II/Roundup Ready Flex (BGII/RRF) provide additional mechanisms for the cotton crop to retain early initiated fruiting structures positioned in the lower canopy. It may be possible, therefore, for early fruit retention to become too high with these new technologies resulting in early cutout and reduced yield. The objective of this investigation was to determine if glyphosate‐induced differences in early season retention occur between BGII/RRF and the older Bollgard/Roundup Ready (BG/RR) technologies and if so, to test if these differences in retention impact crop maturity, yield, or quality under irrigated and nonirrigated conditions. A study was conducted in 2004 and 2005 at two locations in southwestern Georgia to compare the two technologies under dryland vs. irrigation with or without flower removal. The BG/RR matured later than BGII/RRF when glyphosate was applied late at the seventh and 11th leaf stages. The BG/RR compensated for fruit loss by producing heavier remaining bolls. The BGII/RRF maturity was unaffected by the late glyphosate applications and produced a higher percentage of plants having a harvestable boll in the lower canopy than BG/RR. The BGII/RRF cotton had increased boll number and weight at the first sympodial position at lower main stem nodes while BG/RR produced more and heavier bolls on upper main stem nodes. Flower removal did not negatively affect BGII/RRF or BG/RR yields. Few differences in fiber quality were observed. The BGII/RRF retained more early reproductive structures than BG/RR but also cutout earlier. Yield differences between the two technologies may be due to agronomic performance of the variety backgrounds used.

Jost, P.; Shurley, D.; Culpepper, S.; Roberts, P.; Nichols, R.; Reeves, J.; Anthony, S.

doi: 10.2134/agronj2006.0259pmid: N/A

Transgenic cotton (Gossypium hirsutum L.) cultivars produce lint and seed and their propriety traits provide part of the crop's insect management and/or enable use of broad‐spectrum herbicides for weed management. The standard procedures for conducting official cultivar trials utilize common pest management across all cultivars; whereas the pest management options and their associated potential for cost reductions are principal features of current transgenic cultivars. Field experiments were conducted to compare production systems utilizing cotton cultivars possessing different transgenic technologies managed in accordance with their respective genetic capabilities. In 2001 and 2002, selection of the Roundup Ready (RR) technology system resulted in reduced returns to the producer, while higher returns were attained from nontransgenic, Bollgard (B), and Bollgard/Roundup Ready (BR) technologies. In 2003, selection of the RR technology system or the Bollgard II/Roundup Ready (B2R) system reduced returns, while similar, higher returns were attained from nontransgenic, B, and BR technologies. In 2004, a nontransgenic system was superior to the BR, B2R, and Liberty Link (LL) systems in Tifton, but similar returns were achieved from nontransgenic, BR, and B2R technologies in Midville. Cultivar selection was important among the technology systems. Collectively these results indicate that profitability was most closely associated with yields and not the transgenic technologies.

Massey, Raymond E.; Myers, D. Brenton; Kitchen, Newell R.; Sudduth, Kenneth A.

doi: 10.2134/agronj2007.0057pmid: N/A

For over a decade, farmers have been collecting site‐specific yield data. Many have formed doubts about this investment because of their inability to directly apply this information as feedback for improving management. The objective of this case‐study analysis was to investigate how site‐specific decisions can be improved by transforming a long‐term multiple‐crop yield‐map dataset into profit maps that contain economic thresholds representing profitability zones. Ten years (1993–2002) of cleaned yield map data [4, 5, and 1 yr for corn (Zea mays L.), soybean [Glycine max (L.) Merr.], and grain sorghum (Sorghum bicolor L.), respectively] were collected for a 35.6‐ha claypan‐soil field in Missouri. Actual input costs and crop prices, published custom rates for field operations, and region‐specific land rental prices were used to transform yield maps into profitability maps by year, by crop, and overall for 10 yr. Profit maps revealed large field areas where net profit was negative, largely due to negative profit from corn production on areas where topsoil was eroded. The areal extent and degree to which other unique field features affected profitability, such as a tree line and a drainage way, are discussed. This analysis demonstrates how changing yield into profitability metrics can help a producer consider and then decide on different management options. We explore how assessment and exploratory analysis with profitability mapping supports multiple aspects of the decision process, including identification, development, and selection. The decision process discussed supports a producer's need to manage fields with incomplete information and where satisficing rather than optimizing behavior often occurs. This analysis demonstrated how profit mapping can be of value for a producer and provides impetus for the precision agriculture community to consider profit mapping protocols and standards.

Inman, D.; Khosla, R.; Reich, R.; Westfall, D. G.

doi: 10.2134/agronj2007.0020pmid: N/A

Spectral vegetation indices such as the normalized difference vegetation index (NDVI) have been shown to be useful for indirectly obtaining crop information such as photosynthetic efficiency, productivity potential, and potential yield. The objectives of this study were (i) to examine the relationships among NDVI determined early in the growing season, soil color‐based management zones (SCMZ), and relative maize (Zea mays L.) grain yield and (ii) to determine if coupling soil color‐based management zones with NDVI improves the accuracy of soil color‐based management zone precision crop management strategy. Remotely sensed imagery was acquired by aircraft at approximately the eight‐leaf crop growth stage (V8). Kappa statistics and percent areal agreement suggested a slight to substantial areal association among NDVI and relative grain yield (K = 0.10 to 0.63; % areal agreement = 13–67). Regression models were variable and explained among 25 to 82% of the variability in relative grain yield. Inclusion of soil color‐based management zones in the regression models resulted in marginal improvements. When the affects of soil color‐based management zones were removed, NDVI accounted for among 10 to 47% of the variability. The NDVI determined early does have potential to be useful in irrigated maize cropping systems. Coupling NDVI and SCMZs did not bring additional benefits to our soil color‐based management zone strategy.

Liang, X. Q.; Li, H.; He, M. M.; Chen, Y. X.; Tian, G. M.; Xu, S. Y.

doi: 10.2134/agronj2006.0191pmid: N/A

Because excessive application of N fertilizer for crop production leads to environmental pollution and low N utility efficiency, a better understanding of the effects of N application rates on crop yields and NO3–N leaching is required for developing optimum ecological N management that reduces NO3–N leaching while keeping crop yield. Field experiments at two sites in the Taihu region of China were conducted to study the ecologically optimum application of N in wheat (Triticum aestivum L.) season of rice (Oryza sativa L.)–wheat cropping system. The experiment at either site had five N rates on wheat (0–360 kg N ha−1 in 90‐kg increments) and NO3–N in leachate were collected by wedge‐shaped fiberglass wick lysimeters. At either site, the N‐wheat yield quadratic response curve was fitted quite well and a significantly linear relationship between N rates and seasonal NO3–N masses in leachate was also found. The calculated economically optimum N rate for wheat was more site related than depending on changing growing conditions from year to year, while the ecologically optimum N rate was significantly different both at sites and growing conditions (P = 0.01). The results suggest that applying the ecologically optimum N rates of 120–180 kg N ha−1 to wheat is beneficial for maximally reducing NO3–N leaching loss but minimally decreasing yield.

Lawrence, J. R.; Ketterings, Q. M.; Cherney, J. H.

doi: 10.2134/agronj2007.0071pmid: N/A

Decomposition of forage legume‐grass (FLG) sods after turnover will supply N to the next corn (Zea mays L.) crop. For optimum economic grain production typically a starter N application is sufficient. However, the impact of eliminating sidedress N on yield and quality of silage corn in the year after sod turnover (FYC) is not well documented and little is known about the effects of timing of sod turnover (fall or spring) or sod composition (percentage legume) on N fertilizer needs of FYC. In 2005 and 2006, 13 on‐farm and three research station N trials were conducted throughout New York (NY) to determine (i) N needs for optimum yield and quality of FYC and (ii) the impact of FLG composition and timing of sod kill on the likeliness of an economic N fertilizer response. On‐farm trials included four sidedress N rates (0, 56, 112, and 168 kg N ha−1) with a small, banded starter application (34 kg N ha−1 maximum). The three research sites also contained a no starter control. Eliminating the starter resulted in significantly lower yields while sidedress N did not increase yield at any of the 16 sites. Nitrogen application increased crude protein (CP) levels but did not affect other silage quality parameters or estimated milk production. The increase in CP came at great economic (fertilizer) and environmental (low apparent N recovery) costs. We conclude a small starter application is sufficient for optimum yield and quality of FYC regardless of timing of sod turnover or its composition.

Ziadi, Noura; Bélanger, Gilles; Cambouris, Athyna N.; Tremblay, Nicolas; Nolin, Michel C.; Claessens, Annie

doi: 10.2134/agronj2007.0119pmid: N/A

Efficient management of P in crop production requires the development of tools to quantify the P status of plants. Our objectives were to establish the relationship between P and N concentrations of spring milling wheat (Triticum aestivum L.) during the growing season and, in particular, to determine the critical P concentration required to diagnose P deficiency. Shoot biomass and P and N concentrations were determined weekly and grain yield was measured at harvest in an experiment with four to six N rates conducted over 2 yr (2004 and 2005) at three sites with adequate soil P for growth each year. Both shoot P and N concentrations decreased with time as shoot biomass increased during the growing season. They also increased with N fertilization, suggesting that they are closely related. The relationship between shoot P and N concentrations under nonlimiting N conditions is described by a linear function (P = 0.94 + 0.107N, R2 = 0.59, P < 0.001; n = 76) in which concentrations are expressed in g kg−1 dry matter (DM). Under limiting N conditions (relative grain yield <0.80), the relationship was different (P = 1.70 + 0.092N (R2 = 0.48; P < 0.001; n = 19) with greater P concentrations for a given N concentration. These relationships approximate the critical P concentration under both nonlimiting and severely limiting N conditions. This critical P concentration can then be used to quantify the degree of P deficiency during the current growing season.