PHOENIX -- Matt Lawton hit his first grand slam in six years, helping the Pittsburgh Pirates romp over the Arizona Diamondbacks 16-2 tonight for their fifth win in six games.

Lawton went 3-for-5 and had five RBIs for the Pirates, who scored 12 runs in the final two innings. He doubled in a run during Pittsburgh's seven-run ninth against Kerry Ligtenberg.

Daryle Ward hit a three-run homer during the inning, Jack Wilson had a two-run single and Rob Mackowiak had a run-scoring single. The Pirates set season highs for runs and hits (17).

Ty Wigginton had three hits, including his first homer of the year, Humberto Cota had a two-run double, and Kip Wells worked seven solid innings for his third straight win.

Wells (3-3) gave up two runs and four hits, including a solo homer by Luis Gonzalez, and walked three. Gonzalez drew one of the walks and scored Arizona's first run on Chad Tracy's fourth-inning sacrifice fly.

But the Diamondbacks' offense was otherwise down for a second straight game. They had only two hits in a 3-2 loss last night and six in this one.

The Pirates put away the game in the eighth, scoring five runs after Diamondbacks reliever Jose Valverde walked the first two batters and allowed a pinch-hit single to Freddy Sanchez.

Bobby Hill, pinch-hitting for Wells, had an RBI single off Javier Lopez to reload the bases before Lawton drove the first pitch into the right-field seats for his fourth grand slam and first since April 17, 1999, at Cleveland.

Arizona's Brad Halsey (2-1) lost for the first time in seven starts.

Halsey, winless in three starts since beating San Diego 5-3 on April 22, allowed four runs on seven hits and an uncharacteristic four walks in 6 2-3 innings.

He had issued only three walks in 35 innings coming in, but struggled with his control from the start.

Halsey walked Lawton, his first batter, leading to Jason Bay's sacrifice fly.

In the second, Halsey got one out before Wigginton's opposite-field shot cleared the fence in right.

The game remained 2-0 until the sixth, when Jose Castillo lined a single to left and Wigginton beat out an infield hit. Cota, a catcher whose improvement in his second full season gave manager Lloyd McClendon the option of releasing Benito Santiago on Sunday, then lined a double into the left-field corner. Both runners scored when the ball rolled away from Gonzalez along the bullpen fence.

Notes: The Pirates put OF Craig Wilson on the DL before the game and purchased the contract of Ray Sadler from Double-A Altoona. Sadler made a spectacular catch for his first major league putout, chasing Gonzalez's opposite-field liner to the left-field line and then nearly doubling up Alex Cintron at first base. ... The Pirates have had an extra-base hit in all 30 games. ... Bay doubled in the fourth to extend his hitting streak to seven games. ... Arizona CF Jose Cruz Jr. (sore back) began a rehab assignment by playing five innings for Triple-A Tucson.