BackgroundRiverine ecosystems, highly sensitive to climate change and human activities, are characterized by rapid environmental change to fluctuating water levels and siltation, causing stress on their biological components. We have little understanding of mechanisms by which riverine plant species have developed adaptive strategies to cope with stress in dynamic environments while maintaining growth and development.ResultsWe report that poplar (Populus spp.) has evolved a systems level "stress proteome" in the leaf-stem-root apoplast continuum to counter biotic and abiotic factors. To obtain apoplast proteins from P. deltoides, we developed pressure-chamber and water-displacement methods for leaves and stems, respectively. Analyses of 303 proteins and corresponding transcripts coupled with controlled experiments and bioinformatics demonstrate that poplar depends on constitutive and inducible factors to deal with water, pathogen, and oxidative stress. However, each apoplast possessed a unique set of proteins, indicating that response to stress is partly compartmentalized. Apoplast proteins that are involved in glycolysis, fermentation, and catabolism of sucrose and starch appear to enable poplar to grow normally under water stress. Pathogenesis-related proteins mediating water and pathogen stress in apoplast were particularly abundant and effective in suppressing growth of the most prevalent poplar pathogen Melampsora. Unexpectedly, we found diverse peroxidases that appear to be involved in stress-induced cell wall modification in apoplast, particularly during the growing season. Poplar developed a robust antioxidative system to buffer oxidation in stem apoplast.ConclusionThese findings suggest that multistress response in the apoplast constitutes an important adaptive trait for poplar to inhabit dynamic environments and is also a potential mechanism in other riverine plant species.

most efficient crop nutrient utilization potential (Burns et al., 1987;King et al., 1990; Westerman et al., 1983). Efficient crop utilization of N and P derived from anaerobic swine King et al. (1990) reported soil profile NO Ϫ 3 -N accumu-(Sus scrofa domesticus ) lagoon effluent is critical to minimizing offsite nutrient movement. The objective of this study was to determine the lation Ͼ35 mg kg Ϫ1 below a depth of 60 cm after 11 yr of effects of variable rates of swine lagoon effluent and fertilizer N and applying 1340 kg ha Ϫ1 effluent N and noted appreciable P on yield and nutrient utilization of forage grasses on an acid Vaiden profile NO Ϫ 3 -N periodically with 670 kg ha Ϫ1 effluent silty clay (very fine, montmorillonitic, thermic, Vertic Hapludalf) and N. They concluded that a rate of 335 kg N ha Ϫ1 would an alkaline Okolona silty clay (fine, montmorillonitic, thermic, Typic not pose a pollution hazard to ground water. Chromudert). Treatments were multiple effluent irrigations resulting Crop recovery of effluent-derived nutrients is variable in four N and P rates from 0 to 665 and 0 to 94 kg ha Ϫ1 yr Ϫ1 N and and depends on the rate applied. In a study by Burns P, respectively. Fertilizer treatments were also established at equivaet al. (1985) on loamy sands, N recovery by 'Coastal' lent N and P rates. Similar growth responses were obtained for bermubermudagrass across a 7-yr period averaged 73, 57, and dagrass [Cynodon dactylon (L.) Pers.] or johnsongrass [Sorghum 34% for swine effluent N rates of 335, 670, and 1340 kg halepense (L.) Pers.] regardless of nutrient source. Application of either effluent or fertilizer at rates Ͼ448 kg N ha Ϫ1 did not effectively ha Ϫ1 , respectively. Phosphorus recovery was 41, 28, and increase dry matter yield. Total N accumulation reflected both increas- MATERIALS AND METHODS

Runoff water following a rain event is one possible source of environmental contamination after a manure application. This greenhouse study used a rainfall simulator to determine bacterial-associated runoff from troughs of common bermudagrass [Cynodon dactylon (L.) Pers.] that were treated with P-based, N-based, and N plus lime rates of poultry (Gallus gallus) litter, recommended inorganic fertilizer, and control. Total heterotrophic plate count (HPC) bacteria, total and thermotolerant coliforms, enterococci, staphylococci, Clostridium perfringens, Salmonella, and Campylobacter, as well as antibiotic resistance profiles for the staphylococci and enterococci isolates were all monitored in runoff waters. Analysis following five rainfall events indicated that staphylococci, enterococci, and clostridia levels were related to manure application rate. Runoff release of staphylococci, enterococci, and C. perfringens were approximately 3 to 6 log10 greater in litter vs. control treatment. In addition, traditional indicators such as thermotolerant and total coliforms performed poorly as fecal indicators. Some isolated enterococci demonstrated increased antibiotic resistance to polymixin b and/or select aminoglyocosides, while many staphylococci were susceptible to most antimicrobials tested. Results indicated poultry litter application can lead to microbial runoff following simulated rain events. Future studies should focus on the use of staphylococci, enterococci, and C. perfringens as indicators.

potential for decreasing the amount of symbiotic N 2 fixation. In contrast, Lory et al. (1992) reported that Although most of the N required by soybean [Glycine max (L.) topdressed manure addition to alfalfa (Medicago sativa L.)

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Poultry litter is generated in large quantities in the same southeastern U.S. states where cotton (Gossypium hirsutum L.) is a dominant field crop, but is rarely used as a primary cotton fertilizer partly because of lack of adequate management recommendations. This research was conducted to determine adequate rates of broiler litter and whether supplementation with inorganic N would be necessary for optimum cotton lint yield and fiber quality. The research was conducted from 2002 to 2004 on two commercial farms representing conventional‐till (CT) and no‐till (NT) systems. The treatments consisted of an unfertilized control, a farm standard (STD) fertilized with inorganic fertilizers, and broiler litter of 2.2, 4.5, and 6.7 Mg ha−1 in an incomplete factorial combination with 0, 34, or 67 kg ha−1 N as urea–ammonium nitrate solution (UAN). Litter without supplemental UAN–N increased yield by 23 to 110 kg lint ha−1 for every 1.0 Mg ha−1 litter under both CT and NT. The often‐recommended litter rate of 4.5 Mg ha−1 was not adequate to increase yield to be equivalent to that of the STD that received 101 to 135 kg ha−1 as UAN. It was necessary to supplement this or the other litter rates with 34 or 67 kg ha−1. UAN–N to support yield equal to or greater than the yield of the STD. The most consistently well‐performing treatment under both tillage systems in all years was the 4.5 Mg ha−1 litter supplemented with 67 kg ha−1. UAN–N. Lint yield was highly correlated (r2 = 0.83–0.97) with applied total plant‐available N (NTPA) under both systems. Fiber quality, fiber length and micronaire in particular, also responded to NTPA, but the responses were smaller than lint yield. Litter when adequately supplemented with UAN–N did not adversely affect fiber quality. These results show broiler litter as much as 4.5 Mg ha−1 should be supplemented with inorganic N fertilizers when used as a primary cotton fertilizer and when the expected yield is ≈1700 kg ha−1 under CT and ≈1500 kg ha−1 under NT.

Understanding manure nutrient dynamics in soil with any crop is an important management practice for farmers and producers to document accountability and to use manure resources optimally. A field experiment was conducted to quantify input, output, and the year‐round major plant nutrient dynamics in a fine sandy loam soil supplied with 15.75 Mg ha−1 yr−1 broiler litter. Soil samples were collected from pre‐established plots of common bermudagrass [Cynodon dactylon (L.) Pers.] and hybrid bermudagrass cultivars Coastal and Tifton 85 for nutrient analysis. Coastal and Tifton 85 produced significantly greater annual dry matter yield (16948 and 18772 kg ha−1) than common bermudagrass (11238 kg ha−1). Tifton 85 was most efficient and removed 344, 58, and 472 kg ha−1 N, P, and K, respectively. The removal efficiency of these nutrients for Tifton 85 was 73, 18, and 114%, respectively. Soil pH varied from 6.0 to 6.6 until it decreased unexpectedly to 5.6 by the end of 2001. Total soil C increased from 11.4 g kg−1 to 17.9 g kg−1 by the end of the second year. At all sampling dates, the NO3–N concentration was greater than NH4–N while total N decreased during the maximum uptake in late spring and summer. Both total P and Mehlich‐3 extractable P concentrations increased mainly in the 5‐ to 10‐cm depth, indicating slight leaching of P. Results indicated that top yield from hybrid bermudagrass cultivars is possible with broiler litter as a sole fertilizer source. However, considerable nutrient imbalances in soil may occur in the long term if improper litter rates are used.

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