Agronomy Journal

Atkinson, Jeffrey L.; McCarty, Lambert B.; Liu, Haibo; Faust, Jim; Toler, Joe E.

doi: 10.2134/agronj2011.0383pmid: N/A

A 2‐yr study was conducted to determine the tolerance of a mature Diamond zoysiagrass [Zoysia matrella (L.) Merr.] golf green to reduced light environments (RLE) treated with trinexapac‐ethyl (TE) at 0 and 0.013 kg ha−1 wk−1. Three levels of RLE, 0, 60, and 90%, were imposed to coincide with maximum seasonal growth of zoysiagrass. Plant growth measurements included turf quality (TQ), chlorophyll concentration, clipping yield, and total nonstructural carbohydrates. Zoysiagrass grown in full sunlight and 60% RLE maintained commercially acceptable TQ (≥7) with and without TE throughout Year 1 while 90% RLE treatments fell below an acceptable level 2 mo after study initiation. Sixty percent RLE treatments without TE demonstrated unacceptable TQ during Year 2. Application of TE sustained turf viability in 90% RLE through Year 2. Clipping yield increased in 60% RLE without TE compared to full sunlight treatments. Application of TE to 60% RLE treatments reduced clipping yield 30 to 76% in Year 1. Chlorophyll concentration in 60% RLE treatments was similar 10 wk after RLE implementation compared to full sunlight treatments in Year 1 and higher in Year 2. Total nonstructural carbohydrate concentration of roots, rhizomes, and stolons was similar in full sun and 60% RLE treatments at the end of both years and between 47 and 100% lower in 90% RLE treatments compared to full sun treatments. These results support the use of Diamond zoysiagrass in up to 60% reduced light putting green environments with concurrent use of a gibberellin biosynthesis inhibiting product such as TE.

Severino, Liv S.; Auld, Dick L.; Baldanzi, Marco; Cândido, Magno J. D.; Chen, Grace; Crosby, William; Tan, D.; He, Xiaohua; Lakshmamma, P.; Lavanya, C.; Machado, Olga L. T.; Mielke, Thomas; Milani, Máira; Miller, Travis D.; Morris, J. B.; Morse, Stephen. A.; Navas, Alejandro A.; Soares, Dartanhã J.; Sofiatti, Valdinei; Wang, Ming L.;

Villamil, María B.; Davis, Vince M.; Nafziger, Emerson D.

doi: 10.2134/agronj2012.0018npmid: N/A

Illinois ranks second in soybean [Glycine max (L.) Merr.] production in the United States with an annual crop value of some $4 billion. To discover what management practices, soil parameters, and environmental conditions enable higher soybean yields, the Illinois Soybean Association (ISA) started in 2010 a state‐wide “Yield Challenge” (YC) program. Enrolled producers established a “challenge” plot and adjoining “standard” practices plot, and agreed to share crop management information, soil samples, and yield data. Our work describes data analyses and findings using data generated under this program. Yields differed between standard and challenge plots across the state, with foliar applications of fungicide and or insecticide resulting in significant yield increases. Using principal component analyses and multiple regression tools, we were able to explain about 54% of the variation in soybean yield for the state in 2010. Within the available data range, delays in planting date and increased row spacing both reduced soybean yields, and tilled fields yielded more than no– tilled soybean fields. We uncovered a negative trend between soybean yield and PC1, formed by soil cation exchange capacity (CEC), dominant cations, and soil organic matter (SOM), likely due to the drainage characteristics of the plots. Yields were also decreased with increasing values of PC3, a variable that includes soil pH, Mn levels, and soybean cyst nematode (SCN) egg count. On the other hand, higher soil test values of P, Zn, Fe, and K, included in PC2, were related to higher soybean yields. We see this as a promising start to identifying management factors that may be addressed as we continue the search for higher soybean yields.

Krueger, Erik S.; Ochsner, Tyson E.; Baker, John M.; Porter, Paul M.; Reicosky, Don C.

doi: 10.2134/agronj2011.0341pmid: N/A

Recent proliferation of large dairies has prompted concern regarding environmental impacts of associated corn silage production and high‐rate manure application. Our objectives were to compare environmental impacts and forage production of monocrop corn (Zea mays L.) silage and rye (Secale cereal L.)–corn silage double‐crop systems with multiple corn planting dates and high‐rate manure application near Morris, MN. From 2007 to 2009, corn for silage was seeded into a silt loam as a monocrop in early and mid‐May and as a double‐crop after rye in mid‐May and early June. Manure was fall applied annually at average total N and P rates of 393 and 109 kg ha−1, respectively. Double‐cropping reduced total forage dry matter (DM) yield 2 of 3 yr and reduced corn DM yield 15 to 25%. Soil NO3–N to 90 cm accumulated at an average rate of 71 kg N ha−1 yr−1 with monocropping, but accumulation was not observed with double‐cropping. Soil organic C concentration from 0 to 5 cm increased in the monocrop (18%) and double‐crop (26%) systems over 3 yr. Average soil solution NO3–N concentration was high with monocropping (52 mg L−1) and double‐cropping (37 mg L−1), but estimated leaching load averaged only 8 kg ha−1 yr−1. Fall and spring ground cover was often less than 10% with monocropping but was usually greater than 30% with double‐cropping. The primary environmental concerns identified for monocrop corn silage were soil NO3–N buildup and inadequate ground cover. Double‐cropping addressed each concern but often decreased forage production.

Geisseler, Daniel; Lazicki, Patricia A.; Pettygrove, G. Stuart; Ludwig, Bernard; Bachand, Philip A. M.; Horwath, William R.

doi: 10.2134/agronj2011.0362pmid: N/A

Optimal manure management that ensures adequate crop nutrition while avoiding pollution problems requires estimates of manure N availability. The present study was performed in the San Joaquin Valley (California) on three dairy forage production fields where liquid manure is applied together with flood irrigation water. The objective of this study was to determine the fate of manure N by combining field measurements with model simulations using the Root Zone Water Quality Model (RZWQM). The average annual N application to corn (Zea mays L.) and winter forage (oat [Avena sativa L.], triticale [× Triticosecale Wittmack], or Sudan grass [Sorghum bicolor (L.) Moench ssp. drummondii (Steud.) de Wet ex Davidse]) was 840 kg N ha−1, while 490 kg N ha−1 was removed with the harvested crops. The irrigation water input to corn ranged from 45 to 128 cm. The RZWQM described crop yield and N uptake well and accurately simulated the seasonal trends in soil moisture and mineral N content in the top 90 cm of the profile; however, the short‐term changes and mineral N estimates for different soil layers were not accurate. For soil nutrient and water dynamics, site‐specific calibration was an essential requirement. The model estimated that between 140 and 320 kg N ha−1 was leached in a 12‐mo period and up to 80 kg N ha−1 was volatilized as NH3, while losses due to denitrification were insignificant in these sandy soils. Field data and model estimates highlight the potential for a more efficient water and N use in the forage systems studied.

Read, John J.

doi: 10.2134/agronj2011.0385pmid: N/A

Because annual ryegrass (Lolium multiflorum L.) exhibits increases in herbage P with increasing soil P, biomass response to N should influence phytoremediation of P‐enriched soils. Field plot (each 2 by 5 m) studies were conducted to determine the effect of six N schemes that provided 112 or 168 kg N ha−1 on uptake of P and soil test P (STP, 0–15‐cm depth) of double‐cropped bermudagrass [Cynodon dactylon L. (Pers.)] and ryegrass. Bermudagrass was previously fertilized with 9 and 18 Mg broiler litter ha−1 in 2004–2007, no litter was applied after 2007. At past litter rate of 9 Mg ha−1, total uptake of P averaged 48.5 kg ha−1 in 2008 and 51.7 kg ha−1 in 2009. Based on initial STP levels in 2007, results in 2009 indicated STP levels decreased by approximately 50 kg ha−1 yr−1, with reductions of 44% at 9 Mg litter ha−1 (104–58 mg kg−1) and 38% at 18 Mg litter ha−1 (173–108 mg kg−1). Averaged across years and litter rates, uptake of P in ryegrass was greater at 168 than 112 kg N ha−1 (35.4 vs. 29.4 kg ha−1, P < 0.01) and ranged from 35.8 kg ha−1 in scheme N5 to 26.7 kg ha−1 in scheme N1. Schemes N5 and N6, with a total rate of 168 kg N ha−1 in March and May, stimulated uptake of P in ryegrass and ryegrass–bermudagrass, but STP levels in 2009 were not lower than a single application of 112 kg N ha−1 in January and March.

Wiggans, Dustin R.; Singer, Jeremy W.; Moore, Kenneth J.; Lamkey, Kendall R.

doi: 10.2134/agronj2011.0395pmid: N/A

Constraints to maize (Zea mays L.) stover biomass harvest may be mitigated by using a living mulch (LM) to offset C exports and control soil erosion. Living mulches can compete with the main crop for resources. The objective of this research was to quantify competitive effects of LM management systems grown in continuous maize with stover removal. Maize was planted into creeping red fescue (CF) (Festuca rubra L.), Kentucky bluegrass (KB) (Poa pratensis L.), and a mixture of CF and white clover (Trifolium repens L.) (MX) LMs in 2008, 2009, and 2010 near Ames, IA. Management treatments were fall strip‐tillage (ST) and no‐tillage (NT), with either a pre‐planting paraquat burn‐down followed by two glyphosate bands (PQ) or glyphosate bands only (GLY). Kentucky bluegrass PQ ST produced similar grain yields (11,230 kg ha−1) all 3 yr as the no LM control (11,810 kg ha−1) with a harvest index (HI) of 0.55 compared to 0.52 in the control, averaged across years. The control produced greater stover dry matter (SDM) (10,110 kg ha−1) 2 of the 3 yr compared to KB PQ ST (8600 kg ha−1). Total groundcover averaged 80% in KB PQ ST compared to only 45% in the no LM control. These results indicate that a combination of herbicide suppression and ST suppresses LMs adequately to maintain competitive maize grain yields. Additional research under varying climatic conditions will further quantify the risk of LM management systems to increase the sustainable stover harvest of maize biomass feedstocks.

Barker, D. W.; Sawyer, J. E.

doi: 10.2134/agronj2012.0030pmid: N/A

Remote sensing that uses active sensors continue to be tested as an N stress detection method and provide in‐season rate adjustments to corn (Zea mays L.). The objectives of the study were to use active canopy sensing to vary in‐season N application at the V10 corn growth stage and compare applied N rate, grain yield, and nitrogen use efficiency (NUE) with N applied before planting. A fertilizer N rate study was conducted in 2009 and 2010 near Ames, IA. Pre‐plant N rates were 0 to 270 kg N ha−1 and then sensor‐based rates were applied in‐season at the V10 corn growth stage. Rainfall events occurred 3 to 5 d after N application each year, providing corn response to the in‐season applied N and increasing relative corn canopy biomass by the V13 growth stage. The pre‐plant applied nitrogen (PP‐N) 270 kg N ha−1 rate used as the N‐reference did not result in the highest green normalized difference vegetative index (GNDVI) or produce the highest grain yields. The pre‐plant plus sensor applied nitrogen (PP+S‐N) recovered corn yield from plant N stress at V10. The best yield recovery with deficit pre‐plant N and sensor‐directed N application rate occurred each year when no pre‐plant N had been applied. Overall, economic optimum nitrogen rate (EONR) and NUE in PP‐N and PP+S‐N were the same. The PP+S‐N application does give corn growers options for addressing in‐season N deficiency and protect yield potential when corn N need is uncertain or when soil N losses are unavoidable.

Bono, Alfredo; Alvarez, Roberto

doi: 10.2134/agronj2012.0011pmid: N/A

Water storage in the soil profile is an important agronomic variable but its measuring is rather difficult for farmers in production fields. We tested the possibility of using samples from the upper soil layers, which are usually taken for soil fertility evaluation, for whole profile water storage estimation. A data set of 712 water profiles from the subhumid‐semiarid portion of the Pampas in Argentina was used, generated under a wide range of soil types, crops, tillage systems, soil cover, and rainfall scenarios. To calculate stored water, soil was sampled up to 140 cm in layers of 20 cm, water content was gravimetrically determined and bulk density also assessed. Polynomial regression and artificial neural networks were used for modeling, randomly partitioning the data set into 75% for model fit and 25% for independent testing. It was possible to estimate with good fit soil profile water storage using as independent variables in regression, or inputs in neural networks, water content in the upper three soil layers (0–20, 20–40, and 40–60 cm) and depth to petrocalcic layer in soils which have this type of horizon. Similar performance was attained with both modeling methods (R2 > 0.93, RMSE = 11% of mean water content). Other soil and environmental properties had only a minor impact on estimations and were dropped from models. Because of its simplicity, regression is the recommend method for estimation of water content in the soil profile for agronomist.

Barbieri, P.; Echarte, L.; Della Maggiora, A.; Sadras, V. O.; Echeverria, H.; Andrade, F. H.

doi: 10.2134/agronj2012.0014pmid: N/A

Reduced row spacing has shown to increase maize (Zea mays L.) yield; however there are conflicting results on whether narrow rows increases maize crop evapotranspiration and/or water use efficiency. This work analyzes the response of maize yield, crop evapotranspiration (ET) and water use efficiency to reduced row spacing under different water and N regimes. Maize crops were grown at Balcarce, Argentina, during two seasons. Treatments included two water regimes (rain‐fed and irrigated), two rows spacing (35 and 70 cm) and two rates of N (i.e., 180 kg N ha−1 or nonfertilized). Soil water content was measured through the growing seasons using a neutron probe, grain yield and shoot dry matter were determined at physiological maturity. Grain yield response to narrow rows ranged from 0 to 23%; it was higher for water limited (i.e., rain‐fed crops) and/or N deficient crops (i.e., nonfertilized crops) and lower for crops with high N fertilization and irrigation. Narrow rows consistently increased (8%) crop ET during the initial stages of crop growth; and N fertilization did not influence ET response to reduced row spacing during this period. Initial differences in ET between row spacing treatments were diluted as the season progressed, and seasonal crop ET was not influenced by row spacing. Reduced row spacing increased water use efficiency for grain production up to 17%; increments were larger in N deficient crops and/or with water limitations but were negligible in N fertilized and irrigated crops.