Maidstone United have been relegated for the first time in their history.
Their 2-0 defeat at Hornchurch means that they will be playing in Ryman South next season, despite winning five of their last seven matches.
"It's disappointing that it's ended the way it's ended," said Maidstone player manager Jay Saunders.
"I can't fault the boys. They've been superb since I started. We go ahead next season and try and get back up," he told BBC Radio Kent.
In other issues to be decided, Chatham Town were relegated from Ryman South.
Welling and Dover both missed out on a Blue Square Bet South play-off place.
And Tonbridge secured a Ryman Premier Division play-off semi-final, while Hythe Town won the Kent League title.
Chatham's fate was sealed following a 1-1 draw with Bognor Regis Town.
They needed to win their last three matches to stand a chance of staying up.
Having won two in a row, they took the lead at home to Bognor Regis, but the visitors equalised to confirm their relegation.
Welling United and Dover Athletic both had big wins but to no avail as they missed out on the Blue Square Bet South play-offs, finishing sixth and seventh respectively.
Dover would only have qualified had they won and two other results went their way.
Martin Hayes' side did their bit, beating St Albans 4-1, two-goal Adam Birchall taking his tally to 45 for the season, but a win for Chelmsford and a draw for Woking earned the final two play-off places.
"We needed a big result to give us a chance for the play-offs and give the fans something to cheer about," said Hayes.
"We did what we had to do but lady luck wasn't smiling on us.
"We heard of a couple of scores at half time which made it difficult.
"That made it tough second half. You could see a few heads going down. But it's over 42 games. It's not what happened at Dartford last week.
"77 points has only just got teams in and that's pretty good going. It's a strong league.
Hayes also feels that their FA Cup run, in which they beat two Football League sides, Gillingham and Aldershot, before going out to Huddersfield in the third round, ultimately cost them.
"I expected us to be in a play-off place, but the FA Cup is a distraction," he said.
"You don't expect to reach the third round like we did and we have fallen away at the tail end.
"It takes a lot out of you. There was a run of games after the cup and you have got to get yourselves back up again. But we messed up and , have thrown away some silly goals."
Tonbridge Angels secured their play-off place for the second time in three years thanks to a final day 2-0 win at Horsham.
Fraser Logan and Scott Kinch scored the second-half goals for the Angels, in a win which guarantees home advantage for Tuesday's semi-final against Harrow Borough and, should they get there, the final.
"I just wanted to get our heads down for these two games," said manager Tommy Warrilow. "And that's what we did.
"It wasn't plain sailing but we got the three points to secure second place."
Warrilow is aware that Tuesday's opponents Harrow have done the double over Tonbridge in the league this season, but the Angels boss is optimistic that history will not repeat.
"That was our plan. To lose twice and get them in the play-offs" he joked.
"It's obviously difficult but we can't play as badly as we did at Harrow.
"Our home form is tremendous. We've lost once in 18 games, and this is a one-off game.
"We have to concentrate on getting Tuesday out of the way and then have the biggest game in the club's history, I would have thought."
The other issue to be decided was the Kent League, which Hythe won by the skin of their teeth.
The East Kent coast side, who also reached this season's FA Cup first round, looked odds on to win for the entire run-in. But it needed a late goal from Brendan Cass in a 2-2 draw at Tunbridge Wells to pip Herne Bay on goal difference.
"It was nerve-wracking at the end," said manager Scott Porter, after his team were 2-0 down at half-time. "I told the lads there was 45 minutes to save their season.
"I'm a very proud man at the minute. The table doesn't lie, but we've put in a heck of a lot of work in the last 10 months.
"We're now ready for the Ryman League. We have been for a couple of years. The club's run right. We can't wait to go up."
Results - Saturday 30 April
Blue Square Bet South Bromley 0-2 Eastleigh Dover Athletic 4-1 St Albans City Ebbsfleet United 1-1 Woking Maidenhead 2-3 Dartford Welling United 4-0 Basingstoke
Ryman Premier League AFC Hornchurch 2-0 Maidstone United Folkestone Invicta 1-4 Lowestoft Town Harrow Borough 1-1 Cray Wanderers Horsham 0-2 Tonbridge Angels Margate 3-3 Kingstonian
Ryman League Division One North Romford 0-3 Thamesmead Town
Ryman League Division One South Burgess Hill Town 1-1 Ramsgate Chatham Town 1-1 Bognor Regis Town Sittingbourne 2-2 Godalming Town Whitstable Town 0-0 Corinthian Casuals Worthing 0-1 Faversham Town
The Safety Net Associates Kent Football League Corinthian 2-5 Greenwich Borough Deal Town 1-0 Beckenham Town Erith Town 0-2 Erith & Belvedere Fisher 0-1 Sevenoaks Town Holmesdale 1-1 Sporting Bengal Utd Lordswood 1-1 Norton Sports Tunbridge Wells 2-2 Hythe Town VCD Athletic 2-3 Herne Bay
Vandanel Kent County League Premier Division Bearsted 2-2 Charlton Athletic Community Brindon Ropes 3-0 Bly Spartans Canterbury City 3-1 Rusthall Hollands And Blair 2-1 Cray Valley Snodland 0-0 Fleet Leisure Stansfield OB Club 4-3 Tonbridge Invicta Sutton Athletic 6-1 Woodstock Park
Division One Chipstead 1-2 Coney Hill Eltham 2-1 Farnbrough OBG Forest Hill Park 2-1 Greenways Sheerness East 1-1 Kennington Sheppey Utd 1-1 New Romney Tudor Sports 1-3 Metrogas University Of Kent 2-3 Bredhurst Juniors
Division Two Bexley 3-3 Hildenborough Blackheath Utd 1-3 Fleetdown Utd Crofton Albion 3-0 Bexlians Lanes End 1-4 Erith 147 Sports Lydd Town 0-0 Saga Sports And Social NK Aces 3-2 Malgo Platt Utd 0-1 Swale Utd
Monday 2 May
Kent Senior Cup Final Dartford v Bromley
Tuesday 3 May
Blue Square Bet South Play-Off Semi-Final Chelmsford City v Ebbsfleet United
Ryman Premier Division Play-Off Semi-Final Tonbridge Angels v Harrow Borough
Saturday 7 May
Ryman Premier Division Play-Off Final Tonbridge or Harrow v Lowestoft or Bury
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