Utilization of treated swine wastewater for greenhouse tomato production.

An integrated system has been developed to recycle waste organics and treated wastewater from a swine farm to make value-added products and to protect the environment from potential contamination. The farm is a farrow-to-wean swine operation with approximately 4,000 sows. A high-strength wastewater (chemical oxygen demand, 18,000 mg/l; total Khejdal nitrogen, 1,600 mg/l; total phosphorus, 360 mg/l) is produced from the swine operation. An ambient-temperature anaerobic digester has been used to treat the swine wastewater and to produce biogas (from an average 475 m3/day in winter to 950 m3/day in summer). The biogas is combusted in an engine to produce electricity (around 900 kW-hr/day). The digester effluent that is rich in nutrients (N, P, and minerals) is then utilized for fertigation for greenhouse tomato production. A trickling nitrification biofilter has been developed to convert ammonium in the effluent into nitrate. The nitrified anaerobic effluent is used as both fertilizer and irrigation water for approximately 14,400 tomato plants in greenhouses. Experimental data indicate that the tomato greenhouses have used approximately 12 m3 of the effluent and 3.84 kg nitrogen per day. At the same time, the greenhouses have a daily yield of 520 kg (37 g/plant) of marketable fruit.

CO(2)-Enhanced Yield and Foliar Deformation among Tomato Genotypes in Elevated CO(2) Environments.

Yield increases observed among eight genotypes of tomato (Lycopersicon esculentum Mill.) grown at ambient CO(2) (about 350) or 1000 microliters per liter CO(2) were not due to carbon exchange rate increases. Yield varied among genotypes while carbon exchange rate did not. Yield increases were due to a change in partitioning from root to fruit. Tomatoes grown with CO(2) enrichment exhibited nonepinastic foliar deformation similar to nutrient deficiency symptoms. Foliar deformation varied among genotypes, increased throughout the season, and became most severe at elevated CO(2). Foliar deformation was positively related to fruit yield. Foliage from the lower canopy was sampled throughout the growing season and analysed for starch, K, P, Ca, Mg, Fe, and Mn concentrations. Foliar K and Mn concentrations were the only elements correlated with deformation severity. Foliar K decreased while deformation increased. In another study, foliage of half the plants of one genotype received foliar applications of 7 millimolar KH(2)PO(4). Untreated foliage showed significantly greater deformation than treated foliage. Reduced foliar K concentration may cause CO(2)-enhanced foliar deformation. Reduced K may occur following decreased nutrient uptake resulting from reduced root mass due to the change in partitioning from root to fruit.

Carbon gain and photosynthetic response of chrysanthemum to photosynthetic photon flux density cycles.

Most models of carbon gain as a function of photosynthetic irradiance assume an instantaneous response to increases and decreases in irradiance. High- and low-light-grown plants differ, however, in the time required to adjust to increases and decreases in irradiance. In this study the response to a series of increases and decreases in irradiance was observed in Chrysanthemum x morifolium Ramat. "Fiesta" and compared with calculated values assuming an instantaneous response. There were significant differences between high- and low-light-grown plants in their photosynthetic response to four sequential photosynthetic photon flux density (PPFD) cycles consisting of 5-minute exposures to 200 and 400 micromoles per square meter per second (mumol m(-2)s(-1)). The CO(2) assimilation rate of high-light-grown plants at the cycle peak increased throughout the PPFD sequence, but the rate of increase was similar to the increase in CO(2) assimilation rate observed under continuous high-light conditions. Low-light leaves showed more variability in their response to light cycles with no significant increase in CO(2) assimilation rate at the cycle peak during sequential cycles. Carbon gain and deviations from actual values (percentage carbon gain over- or underestimation) based on assumptions of instantaneous response were compared under continuous and cyclic light conditions. The percentage carbon gain overestimation depended on the PPFD step size and growth light level of the leaf. When leaves were exposed to a large PPFD increase, the carbon gain was overestimated by 16 to 26%. The photosynthetic response to 100 mumol m(-2) s(-1) PPFD increases and decreases was rapid, and the small overestimation of the predicted carbon gain, observed during photosynthetic induction, was almost entirely negated by the carbon gain underestimation observed after a decrease. If the PPFD cycle was 200 or 400 mumol m(-2) s(-1), high- and low-light leaves showed a carbon gain overestimation of 25% that was not negated by the underestimation observed after a light decrease. When leaves were exposed to sequential PPFD cycles (200-400 mumol m(-2) s(-1)), carbon gain did not differ from leaves exposed to a single PPFD cycle of identical irradiance integral that had the same step size (200-400-200 mumol m(-2) s(-1)) or mean irradiance (200-300-200 mumol m(-2) s(-1)).

Photosynthetic dynamics in chrysanthemum in response to single step increases and decreases in photon flux density.

The time-course of CO(2) assimilation rate and stomatal conductance to step changes in photosynthetic photon flux density (PPFD) was observed in Chrysanthemum x morifolium Ramat. ;Fiesta'. When PPFD was increased from 200 to 600 micromoles per square meter per second, the rate of photosynthetic CO(2) assimilation showed an initial rapid increase over the first minute followed by a slower increase over the next 12 to 38 minutes, with a faster response in low-light-grown plants. Leaves exposed to small step increases (100 micromoles per square meter per second) reached the new steady-state assimilation rate within a minute. Both stomatal and biochemical limitations played a role during photosynthetic induction, but carboxylation limitations seemed to predominate during the first 5 to 10 minutes. Stomatal control during the slow phase of induction was less important in low-light compared to high-light-grown plants. In response to step decreases in PPFD, photosynthetic rate decreased rapidly and a depression in CO(2) assimilation prior to steady-state was observed. This CO(2) assimilation ;dip' was considerably larger for the large step (400 micromoles per square meter per second) than for the small step. The rapid photosynthetic response seems to be controlled by biochemical processes. High- and low-light-grown plants did not differ in their photosynthetic response to PPFD step decreases.