O 5. 1 High nutrient ,100 a. 2 Low input ,800 b. 3 High weed mgmt ,100 b. 4 Reduced till ,100 b

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1 Yield of corn and spelt in relation to nutrient inputs Chuck Mohler Cornell University Spelt 2006 System All N P 2 O 5 K 2 O Yield 1 High nutrient ,400 a 2 Low input b 3 High weed mgmt ,300 a 4 Reduced till ,300 a 5 Chemical ,700 a 1

2 Spelt 2007 System N P 2 O 5 K 2 O Yield 1 High nutrient ,100 a 2 Low input ,800 b 3 High weed mgmt ,100 b 4 Reduced till ,100 b 5 Chemical ,200 a Spelt 2009 (clover in 2007) System N P 2 O 5 K 2 O Yield 1 High nutrient ,000 a 2 Low input ,300 c 3 High weed mgmt ,400 bc 4 Reduced till ,200 d 5 Chemical ,200 a 2

3 Corn 2007 System All N P 2 O 5 K 2 O Yield (bu) 1 High nutrient Low input High weed mgmt Chemical Clover 1.6 T/A Corn 2008 System All N P 2 O 5 K 2 O Yield 1 High nutrient Low input High weed mgmt Chemical Clover 2.3 T/A 3

4 Do high rates of compost and manure pose a problem for weed management? Chuck Mohler, Thomas Björkman Klaas Martens Quirine Ketterings Brian Caldwell The problem Organic cropping systems use compost and manure as nutrient sources Correct application rates are difficult to determine Nutrients released slowly over time Concentration varies Farmers often err on the high side to insure adequate nutrients for crop growth Enough to supply N needs usually applies excess P and K 4

5 Weeds What are optimal application rates for various crops? How do various application rates affect weed populations? The experiments Took place at the Martens Farm History of conservative nutrient inputs Two experiments High solubility chicken manure compost Chicken manure compost made with added carbon source Field scale: ¼ acre plots Rates: 0, 0.25, 0.5, 1.0 and 2.0 X recommended rate of limiting nutrient for the crop that year 5

6 Crops and nutrient applications Year Crop Limiting 1X Rate nutrient Soluble 2004 Corn N clover 1X Rate High OM clover 2005 Soybean K Spelt/clov er 2007 Corn P Clover only Clover only Crop yield responses to compost Rate giving full yield Year Crop Soluble High OM 2004 Corn 0.5X 0.67X 2005 Soybean No response No response 2006 Spelt 0.8X 2.0X 2007 Corn No response (to residual) No response (to residual) 6

7 Weeds Good weed control in all years Weeds probably did not affect yield Measured weed height In four 5 by 2.5 quadrats per plot Computed mean height by quadrat, then mean of these by plot Measured in Aug except spelt in early June 7

8 Height (cm) Weed heights in corn 2004, high OM compost Giant foxtail Lambsquarters Common ragweed Compost rate (relative to conventional recommendation) Weed height did not reach a maximu m as rate increase d Significance of linear regressions Year Crop 2004 Corn 2005 Soybean 2006 Spelt 2007 Corn Weed Lambsquaters Common ragweed Giant foxtail Common ragweed Giant foxtail Soluble ns *** ns * ns * ns + ns High OM ns Powell amaranth *** Lambsquaters + Common ragweed ** Giant foxtail *** Lambsquaters ** Common ragweed ns ns Giant foxtail * ** Powell amaranth ** 8

9 Weed heights 2007, high solubility compost experiment Giant foxtail Height (cm) 60 Powell amaranth Lambsquarte rs Compost rate in previous years (X conventional recommended) Conclusions Every common annual species showed a linear response over the full range of application rates in at least one experiment in at least two of four years. Seed production increases exponentially with weed height (Mohler & Callaway 1995) Thus, applying excessive e compost can potentially contribute to weed problems. Mohler & Callaway J. Appl Ecol 32:

10 Weeds in OCS Grain expt Quirine Ketterings experiment Compared nutrient sources for conventional continuous corn 0, 50, 100, 150, 200, 250 lb/n, or manure to satisfy P requirement 6,800 gal/a manure to satisfy N requirement 19,300 gal/a composted dairy solids to satisfy P req. 20T/A Composted dairy solids to satisfy N req. 34 T/A We counted weeds each year before they sprayed post-emergence herbicide 10

11 Foxtail density after 5 years of treatment /A) Foxtail (number/ CN CP MN MP Treatment Major weed species respond to high fertility rates whereas crops do not Foxtail seems especially responsive Some evidence indicates build up of P (or possibly K is key) New grad student working on this If P is the issue, more use of legumes for N may be advisable What to do with the manure? 11