Nitrogen response surface models of zucchini squash, head lettuce and potato

Abstract

Plants grown at 5 nitrate (N) levels ranging from 2-36 mmol L -1 for lettuce and 2-43 mmol L -1 for zucchini squash and potato were harvested over the growth period to maturity at a minimum of 2 week intervals. Gamma x cubic response surface models fitted actual dry matter growth data quite precisely (R2> 0.98) from which growth and dry matter partitioning could be derived.Total dry matter growth was very responsive to N and maximum growth was predicted to occur at an N level of 14.2 mmol L -1 for lettuce, 18.1 mmol L -1 for zucchini squash and 11.6 mmol L-1 for potato. Growth declined at higher N levels for all species. For zucchini squash, both high and low N levels which reduced growth increased partitioning of dry matter to fruit. For potato, partitioning of dry matter to tubers tended to increase at high levels of N, particularly at maturity. For lettuce, the N level producing the highest dry matter yield partitioned the highest ratio of dry matter to head.The highest fresh yields of zucchini squash fruit, lettuce head and potato tubers were recorded at N levels of 14, 5 and 11 and 7 mmol L -~ respectively. The effect of N on quality followed a similar trend.

Organic matter fractions and N mineralization in vegetable‐cropped sandy soils

“…Our results are in direct relation to investigations of Huett and Dettmann (1991) and Huett and Dettmann (1992) In fact, it was determined that foliar fertilization does not replace soil-applied fertilizer completely but it does increase the uptake and hence the efficiency of the nutrients applied to the soil (Tejada and Gonzalez, 2004). One of the benefits of foliar fertilization is the increased uptake of nutrients from the soil.…”

Nitrate and nitrite in Australian leafy vegetables

“…This is consistent with the study of three lettuce varieties grown under similar light treatments to the Swiss chard study where reduced photosynthetic rates and growth were associated with reduced irradiance (He and Lee 1998). The shape of the growth response curve was similar to that recorded for lettuce grown in sand culture over the same range of nitrate concentrations (Huett and Dettmann 1991). The maximum shoot nitrate concentrations in Swiss chard occurred at optimal to supra-optimal nitrate supply for growth in both the winter and spring experiments, consistent with response studies on rape, Chinese cabbage, and spinach by Chen et al (2004).…”

Cucurbita pepo nitrogen fertigation in greenhouse environments

“…The magnitude of the productivity increase in response to doses of N depends on the division of photoassimilates among plant parts. Although the vegetative part is usually responsive to nitrogen most of the time, the reproductive part may not show biomass increase at the same rate (Huett and Belinda, 1991). In melon plants, fruits are a powerful sink of photoassimilates to the plant (Duarte et al, 2008), which may represent a reduction in the rate of increase for vegetative biomass during the reproductive period.…”