<PAGE>

                                                                  EXHIBIT 10.143

                      LOAN CONTRACT - SECURITY AGREEMENT

<TABLE>
<CAPTION>
-----------------------------------------------------------------------------------------------------------------------------------
GOODS PREVIOUSLY  CONSTRUCTION      DEALER ACCOUNT   DEALER PHONE NO.  APPLICATION DATE  DATE ACCEPTED BY JOHN DEERE   CONTRACT NO.
SETTLED FOR?                        NUMBER                                               CONST EQMT CO
<S>               <C>               <C>              <C>               <C>               <C>                           <C>
YES [_] NO [_]    NEW [_] USED [X]  17-0908          801-262-7441      19 OCT 00         OFFICE USE ONLY               17-880171959
-----------------------------------------------------------------------------------------------------------------------------------
Seller's Name and Address
SCOTT MACHINERY CO. 4055 S. 500 W. SALT LAKE CITY, UT 84123
-----------------------------------------------------------------------------------------------------------------------------------
Borrower's (Debtor's) Name (Last Name First) and Mailing Address   Borrower's (Debtor's) Name (Last Name First) and Mailing Address
(Including County and Zip)                                         (Including County and Zip)
MEADOW VALLEY CONTRACTORS INC
PO BOX 60726
PHOENIX, AZ 85082
-----------------------------------------------------------------------------------------------------------------------------------
Borrower's (Debtor's) Phone No.      Borrower (Debtor) Resides in (County/State)      Borrower (Debtor) Agent to keep Goods in
602-437-5400                         PHOENIX, AZ                                      County/State PHOENIX, AZ

Place of Filing (Town & State)
AZ-SOS
-----------------------------------------------------------------------------------------------------------------------------------
Borrower's Social Security Number (First Signer) or Tax Id Number                      Type of Business
                                                                      ----------------------------------------------------
                                                                      Proprietor [_] Partner [_] Corporation [_] L.L.C [_]

Name and Title of Signing Officer (If Corporation or LLC)
BRADLEY LARSON                               PRESIDENT
-----------------------------------------------------------------------------------------------------------------------------------
</TABLE>

APPLICATION AND PROMISSORY NOTE: I hereby apply to John Deere Construction
Equipment Company (together with its assigns, the "Lender") for a Loan in the
amount of the Principal Balance shown below. The amount of the unpaid balance on
line 3 is to be used to finance the Balance Due on the purchase order executed
in connection with the purchase from the Seller of the equipment described below
(the "Goods"). If this Loan Contract is accepted by Lender, I promise to pay to
the order of Lender, the Principal Balance, shown on line 7 below, and finance
charges thereon computed on the daily unpaid balance of the Principal Balance
and to pay the installments shown below, with such adjustments in the amount or
number of installments as may be necessary to reflect actual finance charges
earned. If more than one person signs this Agreement as "Borrower"), we will be
jointly and severally liable for all amount due under this Agreement. Except for
the Notice to Borrower section. In this Agreement, the words "I" and "me" and
"my" mean the persons, whether one or more, who sign it as the "Borrower".

<TABLE>
<CAPTION>
-----------------------------------------------------------------------------------------------------------------------------------
Quality     New/Used      Manufacturer        Model       Goods (Equipment)      Product Identification No.     Delivered Cash Price
-----------------------------------------------------------------------------------------------------------------------------------
<S>         <C>         <C>                   <C>         <C>                    <C>                            <C>
   1           U        JOHN DEERE            270LC        1997 EXCAVATOR            FF0270X070059                     $169,000.00
-----------------------------------------------------------------------------------------------------------------------------------

-----------------------------------------------------------------------------------------------------------------------------------

-----------------------------------------------------------------------------------------------------------------------------------

-----------------------------------------------------------------------------------------------------------------------------------
Quantity   Manufacturer     Model      Description of Trade-In (From Purchase Order)      Product Identification No.       Amount
-----------------------------------------------------------------------------------------------------------------------------------

-----------------------------------------------------------------------------------------------------------------------------------

-----------------------------------------------------------------------------------------------------------------------------------

-----------------------------------------------------------------------------------------------------------------------------------
CASH DOWN PAYMENT: $30,200.00                                                                  TOTAL TRADE-IN:                $0.00
-----------------------------------------------------------------------------------------------------------------------------------
         MONTHLY INSTALLMENTS
----------------------------------------
Number of    Amount of   First Payment
Payments   Each Payment    Due Date                                    ITEMIZATION OF AMOUNT FINANCED
----------------------------------------
   48         $3,535.36    12/1/00
----------------------------------------------------------------------------------------------------------------------------------
    0             $0.00                     Sales Tax Paid to Government Agencies                                      $  8,813.80
----------------------------------------------------------------------------------------------------------------------------------
    0             $0.00                     Cash Price (including Tax)                                       1         $177,813.80
----------------------------------------------------------------------------------------------------------------------------------
    0             $0.00                     Total Down Payment. Sum of Trade-in and Cash Down Payment        2         $ 30,200.00
----------------------------------------------------------------------------------------------------------------------------------
    0             $0.00                     Unpaid Balance of Cash Price (Paid to Seller)                    3         $147,613.80
----------------------------------------------------------------------------------------------------------------------------------
    0             $0.00                     Official Fees (Paid to Public Officials)                         4         $     10.00
----------------------------------------------------------------------------------------------------------------------------------
    0             $0.00                     Administrative Fees                                              5         $    300.00
----------------------------------------------------------------------------------------------------------------------------------
                                            Insurance - Credit Life and/or Physical Damage                   6         $      0.00
----------------------------------------------------------------------------------------------------------------------------------
Payments are due each successive month on   Principal Balance (Lines 3, 4, 5 and 6)
the same day of the month as the first      The amount of credit provided to Borrower(s)                     7         $147,923.80
payment except as follows:
----------------------------------------------------------------------------------------------------------------------------------
                                            Finance Charge (Based on Line 7)
                                            The dollar amount the credit will cost Borrower(s)               8         $ 21,773.48
----------------------------------------------------------------------------------------------------------------------------------
                                            Total (Lines 7 and 8). (Principal Balance plus Finance Charge)   9         $169,697.28
----------------------------------------------------------------------------------------------------------------------------------
DATE FINANCE CHARGE BEGINS: 11/1/00         Annual Interest Rate:
                                            The cost of the Borrower(s) credit as a yearly rate.                              6.90%
----------------------------------------------------------------------------------------------------------------------------------
</TABLE>

SECURITY AGREEMENT: To secure the indebtedness evidenced by the contract I
grant you a Security Interest in the Goods (which term includes items, if any,
listed as "Security" or "additional security") and all parts and accessories now
or hereafter incorporated in or on such Goods by way of addition, accession or
replacement and any proceeds arising therefrom, including, without limitation,
insurance proceeds. I agree that I have received the Goods. Lender can inspect
the Goods at any reasonable time. I REPRESENT THAT THE GOODS ARE BEING PURCHASED
FOR A BUSINESS OR COMMERCIAL PURPOSE.

EARLY PAYMENT: I may prepay may obligation in full at any time prior to the
original or any extended maturity and will be charged only for earned Finance
Charges. No penalties will be imposed for early payment).

DELINQUENCY CHARGE; NSF FEES: For each installment not paid when due, I promise
to pay Lender a delinquency charge calculated at the rate of 1.5% per month for
the period of the delinquency or, at Lender's option, 5% of such installment
provided that such a delinquency charge is not prohibited by law, otherwise at
the highest rate allowed by applicable law. I agree to repay immediately to
Lender in the enforcement or administration of its rights under this Agreement,
including, without limitation, any amount paid by Lender to a depository
institution because a check, draft or order made or drawn by or for the benefit
of me is returned unpaid for any reason. If any payment is made by a check which
is dishonored, I agree to pay Lender a fee of $20 or such lesser amount
specified by applicable law.

STATE LAW APPLYING: THE CONSTRUCTION AND VALIDITY OF THIS AGREEMENT SHALL BE
CONTROLLED BY THE LAW OF IOWA, AND THE VALIDITY OF THE SECURITY INTEREST SHALL
BE CONTROLLED BY THE LAW OF THE STATE WHERE THE GOODS ARE TO BE KEPT AND USED.

-----------------------------------------------------------------------------
 ADDITIONAL PROVISIONS CONCERNING RIGHTS OF THE PARTIES ON REVERSE SIDE ARE A
                             PART OF THIS CONTRACT
-----------------------------------------------------------------------------

<TABLE>
<S>                                                              <C>   <C>      <C>
-----------------------------------------------------------------------------------------------------------------------------------
INSURANCE DISCLOSURES: I may obtain Physical Damage Insurance    No.            I want Physical Damage Insurance (Sign in this box)
from anyone I want that is acceptable to Lender. If I get        MOS   PREMIUM
this insurance through Lender, I will pay the Premium shown      0     $0.00
at right. No insurance will be provided unless I sign at the
right, the premium is shown and Lender accepts the contract.
-----------------------------------------------------------------------------------------------------------------------------------
Credit Life Insurances is not required to obtain credit and      No.            I want Credit Life Insurance (Sign in this box)
will not be provided unless I sign at the right, the premium     MOS   PREMIUM
is shown and Lender accepts this contract.                       0     $0.00                                               Age:
-----------------------------------------------------------------------------------------------------------------------------------
</TABLE>

NOTICE TO BORROWERS: 1. Do not sign this contract before you read it or if it
contains blank spaces. 2. You are entitled to an exact and completely filled in
copy of this contract when you sign it. Keep it to protect your rights. 3. Under
the law, you may have the right to redeem the property if repossessed for a
default within the time provided by law.

CAUTION: IT IS IMPORTANT THAT YOU THOROUGHLY READ THE CONTRACT BEFORE YOU SIGN
IT. I acknowledge receipt of a true copy hereof.

<TABLE>
<S>                                                             <C>         <C>
MEADOW VALLEY CONTRACTORS, INC.                                             DO NOT WRITE IN SHADED AREA - FOR DEERE CREDIT
                                                                                        SERVICES, INC..
                                                                                           USE ONLY

                                                                            ------------------------------------------------------
   /s/ Kenneth D. Nelson                            VICE PRES    10-24-00   Accepted by: JOHN DEERE CONSTRUCTION EQUIPMENT COMPANY
-------------------------------------------------------------   ----------
Borrower's (Debtor's) Signature   KENNETH D NELSON    Title        Date                    (Leader/Secured Party)

                                                                            Ads: 1415 28th Street PO Box 65090, West Des Monies,
                                                                                 Iowa 50265-0090
                                                                                 --------------------------------------------------
_____________________________________________________________   __________
Borrower's (Debtor's) Signature                       Title        Date     By:
                                                                                 ________________________     _____________________
                                                                                  (Authorized Signature)               Date
_____________________________________________________________   __________  -------------------------------------------------------
Borrower's (Debtor's) Signature                       Title        Date
</TABLE>
<PAGE>

            ADDITIONAL PROVISIONS CONCERNING RIGHTS OF THE PARTIES

APPLICATION OF PAYMENTS: Any sums received from me may be applied at Lender's
discretion to obligations hereunder or to any other indebtedness owed by me to
Lender despite directions, if any, appearing on the remittance, and to interest
principal, and if permitted by law to past due interest before installments. If
any proceeds from the sale of the Goods or insurance are applied to the debt, I
remain liable to make each monthly payment described in this contract until it
is paid in full. Lender may accept payments marked "paid in full" or with other
restrictive endorsements, without losing any of your rights under this
Agreement.

DEFAULT: This contract shall be in default (a) if I fail to pay any installment
when due; (b) if I attempt to sell or encumber any interest in the Goods; (c) if
I institute or have instituted against me proceedings under any bankruptcy or
insolvency law; (d) if I make an assignment for the benefit of creditors; (e) if
I fail to pay taxes levied on the Goods; (f) if any attachment, execution, writ,
or other process is levied against any of my property; (g) if I fail at any time
to keep the Goods properly insured as described below; (i) if I fail to maintain
the Goods in good condition and repair or permit its value to be impaired; (j)
if I permit the Goods to be used in violation of any law, regulation or policy
of insurance; (k) if any representation, warranty or statement is made to Lender
in connection with this agreement which is false in any material respect when
made; (l) if any legal entity such as a partnership, limited liability company
or corporation) that has agreed to pay this agreement ceases to do business,
dissolves, liquidates its assets or terminates or fails to maintain its legal
existence; (m) if I fail to comply with any other provision of this contract: or
(n) if for any reason Lender deems the debt or security unsafe. If any such
event Lender may take possession of any Goods in which Lender has a Security
Interest and exercise any other remedies provided by law. In such event I agree,
upon demand, to assemble the Goods at a location designated by Lender, and
Lender may immediately and without notice declare the entire balance of this
contract due and payable. In addition, to the extent permitted by law, Lender
may collect all reasonable expenses, including attorney's fees, incurred in
realizing on the security interest granted hereunder, or otherwise enforcing the
terms of this contract. If I reside in Texas, I agree that any remaining amounts
due under this contract after any default by me shall be payable to Lender or
its order at Dallas, in Dallas County, Texas.

If Lender takes possession of the Goods after I default, it shall be
commercially reasonable for Lender to sell; (i) the Goods at a private sale;
(ii) at wholesale to a dealer in used goods of like kind; or (iii) at retail to
a purchaser directly or through a dealer in such used goods. The enumeration of
the foregoing methods of disposition are without limitation to the Lender's
right to dispose of the Goods by any other manner or method (whether by sale,
lease, or otherwise) in a commercially reasonable manner. Lender also has the
right to take possession of the Goods or render the Goods unusable. Upon
default, I grant Lender permission to cancel any insurance on the Goods and if
allowed by law, to apply an premium refunds to my debt to Lender with any excess
returned to me. Waiver of any breach or default shall not constitute a waive of
any other or subsequent breach or default.

RISK OF LOSS AND OTHER AGREEMENTS. I hold the Goods at my risk and expense with
no abatement in any obligation on account of loss or damage. I will settle all
claims of any kind against the seller of the Goods directly with the seller and
I will not use any such claim as a defense, setoff or counterclaim against any
effort by Lender to enforce this Contract. I authorize Lender to file (or to
execute on my behalf and file) a financing statement (or statements) in order to
perfect the security interest granted herein, indicating the type of items
described herein or describing such items. Each person who signs this Agreement
agrees that any carbon signature, facsimile signature or electronic signature
shall constitute an original signature within the meaning of applicable law, for
all purposes, including the filing of financing statements. Lender may correct
patent or clerical errors in the Agreement, or any purchase order or financing
statement executed in connection with the transactions contemplated in this
Agreement. Any provision of this Agreement prohibited by law shall be
ineffective and deemed deleted to the extent of such prohibition and shall not
invalidate any other provision hereof.

INSURANCE: Except to the extent this Agreement is for service work, I will at
all times keep the Goods insured against all risk of loss, damage or destruction
for greater or their full insurable value or the then outstanding amount of this
Loan. Lender must be listed as a loss payee. I may choose the person through
whom I obtain the insurance but the insurance must be acceptable to Lender. Such
insurance will provide that it may not be canceled by me without Lender's
consent and may not be canceled by the insurance company without at least (10)
days written notice to Lender. I will provide Lender with evidence of the
paid-up insurance on the Goods within fifteen (15) days of the date of this
contract and at least thirty (30)days before the renewal date. If I fail to
provide evidence of the insurance within the time periods specified in the
preceding sentence, then I will reimburse Lender for the cost of any insurance
Lender purchased until the date such evidence is provided by me. If I fail to
keep the Goods properly insured, Lender may, but is under no obligation to, buy
insurance to protect the Goods and add the cost to my debt to Lender, and I
promise to pay additional cost upon Lender's demand. To the fullest extent
permitted by law, I will pay Lender a reasonable administrative fee for
obtaining and canceling such insurance.

I may meet this insurance requirement by having Lender purchase such insurance.
Inclusion of any amount of Physical Damage Insurance in the Insurance Disclosure
box on the front of this contract will be election to do this, but such
insurance will only be purchased if Lender accepts this Agreement. Such
insurance will cover only the fair market value of the Goods at the time of the
loss. If the term of such insurance is less than the term of this Agreement, I
will, upon termination of such insurance, purchase insurance to fulfill my
obligation to insure hereunder.