Saturday, 15 July 2006

Mulch and Nitogen Fertilizer Effects on Pumpkin Yield and Quality.

A. Wyenandt and J. Heckman. Rutgers Univ, Plant Biology and Pathology Dept, 59 Dudley Rd, New Brunswick, NJ 08831

Many small farmers in New Jersey operate roadside markets which often have U-pick crops or offer some form of ‘agri-tainment' during the growing season. Municipal leaves may be a valuable resource for many small farmers with such operations. Municipal leaves may help create a more attractive, weed-free environment for entertainment agriculture or the U-pick operations which is critically important to attracting and retaining customers. Another, more long-term benefit of incorporating leaf mulch into vegetable production is the potential to build soil organic matter content. A concern with the use of municipal leaves as a soil-surface mulch in vegetable production is the relatively high C:N ratio which may cause immobilization of soil N. Shade tree leaves typically have a C:N ratio of 50:1. This C/N ratio would suggest that a higher than normal N fertilizer application rate may be necessary when growing crops with leaf mulch. The objectives of this study were to determine the effects of municipal leaves and N rate on pumpkin yield, size, and fruit quality (cleanliness). In 2005, a randomized split plot design with 4 replications was conducted at the Rutgers Snyder Research and Extension Farm near Pittstown, NJ. Plots were established on a Quakertown silt loam soil (fine-loamy, mixed, mesic Typic Hapludult) as either bare soil with herbicide for weed control or as 15 cm leaf mulch without herbicide as main plot and N fertility as subplot. Prior to mulch application 280 kg/ha of 20N-4P-8K was broadcast over entire field to supply 56 kg/ha of N at time of planting. On 14 June, pumpkin cv. ‘Magic' Lantern' were seeded by hand at 0.6 m in-row and on 2.1 m centers between rows. Additional N, as ammonium nitrate, was applied to all plots at a rate of 28 kg/ha N on 22 July and at a rate of 56 kg/ha of N to subplots on 2 August. Standard production practices for insect and disease control were followed during the growing season. Chlorophyll meter (SPAD) readings measured 22 July on pumpkin leaves confirmed that crop leaf greenness was reduced on mulch plots as a result of soil N immobilization and N deficiency. The N deficiency induced by leaf mulch was, however, only temporary as the crop quickly recovered following N application. On 8 Sept all pumpkin fruit were harvested, weighed and rated for fruit quality. Weed populations in leaf mulch plots without the use of herbicide was minimal and similar to bare soil plots with herbicide. In general, total number of fruit was higher in bare soil plots compared to leaf mulch. Percentage of orange fruit was higher in bare soil compared to leaf mulch. Total number of orange marketable fruit was higher in bare soil 140 kg/ha N when compared to leaf mulch 140 kg/ha N. There were no significant differences in weight of orange fruit or total weight of harvested fruit between bare soil and mulch plots. The reduction in the number of pumpkin fruit grown on mulch without a reduction in total yield can be attributed to a larger (heavier) fruit weight. Average weight of orange fruit was 5.6 kg on mulch compared to 4.1 kg on bare soil. The percentage of clean fruit at harvest was higher in mulch plots (92% clean) compared to bare soil (18% clean). Results indicate that pumpkins can be successfully produced at comparable yield levels while using municipal leaf mulch to provide weed control. An application rate of N higher than what is generally used for pumpkin appears to be unnecessary, and possibly detrimental to fruit set and maturity, when mulching with municipal leaves.

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