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Raymond Kruse and Ajay Nair

6300; Thermo Fisher Scientific, Cambridge, UK). Fig. 2. Soil nitrogen (N) concentration (nitrate + ammonium) as influenced by cover crop over time in year 2013 and 2014 (control = no-cover crop). Mean separation between treatments at each date by least

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Sidat Yaffa, Bharat P. Singh, Upendra M. Sainju, and K.C. Reddy

Sustainable practices are needed in vegetable production to maintain yield and to reduce the potential for soil erosion and N leaching. We examined the effects of tillage [no-till (NT), chisel plowing (CP), and moldboard plowing (MP)], cover cropping [hairy vetch (Vicia villosa Roth) vs. winter weeds], N fertilization (0, 90, and 180 kg·ha-1 N), and date of sampling on tomato (Lycopersicon esculentum Mill.) yield, N uptake, and soil inorganic N in a Norfolk sandy loam in Fort Valley, Ga. for 2 years. Yield was greater with CP and MP than with NT in 1996 and was greater with 90 and 180 than with 0 kg·ha-1 N in 1996 and 1997. Similarly, aboveground tomato biomass (dry weight of stems + leaves + fruits) and N uptake were greater with CP and MP than with NT from 40 to 118 days after transplanting (DAT) in 1996; greater with hairy vetch than with winter weeds at 82 DAT in 1997; and greater with 90 or 180 than with 0 kg·ha-1 N at 97 DAT in 1996 and at 82 DAT in 1997. Soil inorganic N was greater with NT or CP than with MP at 0- to 10-cm depth at 0 and 30 DAT in 1996; greater with hairy vetch than with winter weeds at 0- to 10-cm and at 10- to 30-cm at 0 DAT in 1996 and 1997, respectively; and greater with 90 or 180 than with 0 kg·ha-1 N from 30 to 116 DAT in 1996 and 1997. Levels of soil inorganic N and tomato N uptake indicated that N release from cover crop residues was synchronized with N need by tomato, and that N fertilization should be done within 8 weeks of transplanting. Similar tomato yield, biomass, and N uptake with CP vs. MP and with 90 vs. 180 kg·ha-1 N suggests that minimum tillage, such as CP, and 90 kg·ha-1 N can better sustain tomato yield and reduce potentials for soil erosion and N leaching than can conventional tillage, such as MP, and 180 kg·ha-1 N, respectively. Because of increased vegetative cover in the winter, followed by increased mulch and soil N in the summer, hairy vetch can reduce the potential for soil erosion and the amount of N fertilization required for tomato better than can winter weeds.

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Thomas G. Bottoms, Timothy K. Hartz, Michael D. Cahn, and Barry F. Farrara

Spectrophotometric determination of nitrate with a single reagent Anal. Lett. 36 2713 2722 Forster, J.C. 1995 Soil nitrogen, p. 79–87. In: Alef, K. and P. Nannipieri (eds.). Methods in applied soil microbiology and biochemistry. Academic Press, San Diego, CA Grattan

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Sanliang Gu, Carlos H. Crisosto, R. Scott Johnson, Robert C. Cochran, and David Garner

Fruit from 8 `Hayward' kiwifruit vineyards in central California were harvested at 2 week intervals after soluble solids content (SSC) reached 6% and subjected to 4 and 6 months of storage at 0°C in an ethylene free environment. Fruit characteristics at harvest and postharvest performance varied considerably among locations. Fruit stored for 6 months had the same fresh weight, less flesh firmness and higher SSC, than the 4 months storage. Later harvested fruit had greater fruit flesh firmness and higher SSC after storage. SSC after storage was predictable based on ripe soluble solids content (RSSC) at harvest. Summer pruning reduced while soil nitrogen application increased fruit SSC.

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W.T. Gondwe and H.C. Wien

The response of corn, beans and potato was evaluated in a 3 crop intercropping system at constant population density of corn (37,050 plants/ha) and three densities of beans (66,000 132,000 200,000 plants/ha) and potato (13,000, 36,000, 44,000 plants/ha) at low soil nitrogen in 2 seasons. Intercropping at the highest plant densities of beans and potatoes reduced the yield of corn, beans and potatoes by 65, 80 and 51 per cent respectively and produced a land equivalent ratio (LER) of one. The LER increased with decrease in the density of companion crops up to 1.24, indicating that intercropping at lower densities was more beneficial than monocultures. Increasing the density of beans and potatoes reduced corn height, leaf width and size of ears as well as leaf N, P and K. In beans the number of pods per plant was reduced while seeds per plant and seed weight were constant. In potatoes tuber size and numbers per plant declined.. The results indicate that the triple crop density which maximizes yield and income should not exceed 2/3 of optimum bean and potato sole crop densities.

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Pengpeng Duan, Ying Sun, Yuling Zhang, Qingfeng Fan, Na Yu, Xiuli Dang, and Hongtao Zou

nitrite by extraction-distillation methods Soil Sci. Soc. Amer. J. 30 577 582 Brookes, P.C. Landman, A. Pruden, G. Jenkinson, D. 1985 Chloroform fumigation and the release of soil nitrogen: A rapid direct extraction method to measure microbial biomass

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Ibukun T. Ayankojo, Kelly T. Morgan, Davie M. Kadyampakeni, and Guodong D. Liu

Djidonou, D. Zhao, X. Simonne, E.H. Koch, K.E. 2013 Yield, water-, and nitrogen-use efficiency in field-grown, grafted tomatoes HortScience 48 485 492 Dou, H. Alva, A.K. Appel, T. 2000 An evaluation of plant-available soil nitrogen in selected sandy soils

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Shichao Wang, Zhujun Chen, Jun Man, and Jianbin Zhou

Sinica (ISSAS) 1995 China’s Soil Classification Systems. China’s Agricultural Science and Technology Press, Beijing Ji, J.H. Zhang, Y.L. Zhang, Y.L. Yu, N. Zou, H.T. Li, Y.Y. Liu, S.Q. Tong, Y.X. 2014 Soil nitrogen mineralisation dynamics under long

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Luther C. Carson, Monica Ozores-Hampton, Kelly T. Morgan, and Steven A. Sargent

Florida best management practices include the use of controlled-release fertilizers (CRFs), which are soluble nutrients coated with a resin, polymer, sulfur, or a polymer covering a sulfur-coated urea. The purpose of this study was to compare the effects of three CRFs (coated, homogenized NH4NO3 and urea, and coated KNO3) rates in a hybrid CRF/soluble nitrogen fertilizer (SNF) system and two SNF rates [University of Florida/Institute of Food and Agricultural Science (UF/IFAS) and grower standard] on seepage-irrigated fall tomato (Solanum lycopersicum L.) yields, leaf-tissue nitrogen (LTN) concentration, postseason soil nitrogen (N) content, and postharvest fruit quality. Treatments of 112, 168, and 224 kg·ha−1 CRF N plus 56 kg·ha−1 SNF for total N of 168 (CRF112/SNF56), 224, and 280 kg·ha−1 were compared with IFAS (224 kg·ha−1) and grower standard (280 kg·ha−1) of pre-plant SNF. Tomatoes were planted on 29 Aug. 2011 and 3 Sept. 2012 on polyethylene mulch. Air temperature averaged 23.0 and 22.6 °C for the 2011 and 2012 fall seasons with 33.4 and 37.4 cm of rainfall, respectively. Soil temperatures ranged from 15.2 to 40.1 °C in 2011 and 13.6 to 36.6 °C in 2012. Leaf tissue N concentration exceeded the UF/IFAS-recommended sufficiency range for all treatments and sample dates, except CRF112/SNF56 at the last sample date of 2012. There were no differences in extra-large and total marketable yield at first harvest nor in total extra-large yield (three harvests combined) among treatments in 2011; however, total marketable yield for UF/IFAS, CRF112/SNF56, 168/SNF56, and 224/SNF56 was greater than that of the grower standard. In 2012, CRF112/SNF56 and CRF168/SNF56 had the greatest first harvest extra-large and total yield, but there were no differences between season total marketable yields. No differences between treatments were found for total N remaining in the soil postseason in 2011 or 2012. The grower standard, UF/IFAS, and CRF112/SNF56 were firmer at red ripe (less fruit deformation) in 2011, but there were no differences in 2012. In 2011, CRF112/SNF56 and CRF224/SNF56 were rated highest in red color among the treatments, and in 2012 there were no differences. A hybrid system containing lower and equal N rates (112 to 168 kg·ha−1 CRF N and 56 kg·ha−1 SNF56) compared with UF/IFAS-recommended rates produced comparable marketable yield and fruit quality.

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Juan Carlos Gilsanz, D. C. Sanders, and G. D. Hoyt

Rye plus crimson clover cover crops were followed by spring potato and fall snap bean or sorghum or fallow. The soil samples at 15 cm increments to 90 cm were evaluated for nitrate levels after each crop and cover crop. After the cover crops, soil nitrate levels were reduced relative to the fallow area. After the potato, crop soil nitrate levels increased above initial spring levels due a uniform fertilization due to the amount of N applied and short cycle of the crop. Snap beans and sorghum had increased plant stands and reduced soil impedance after fall cover crops. HOW nitrate levels varied with soil depth and time will be discussed.