The Senate last night voted 58 to 38 against deleting from a pending public works appropriations bill production funds for a generation of neutron weapons.

The vote came on an amendment by Sen. Mark O. Hatfield (R-Ore.).

Senators then began searching for some means to give Congress a second vote on the neutron issue after President Carter decides whether he will proceed with production, Carter has said he will make that decision after receiving a Defense Department study Aug. 15.

The President on Tuesday called on Congress to vote the neutron money now, since his initial view was that the weapons "were in the national interest."

Hatfield had argued that "almost hourly or daily developments" showed there was a "knowledge vacuum" in the Senate about the weapons.

"To move at this point," Hatfield said, "would be ill-timed and ill-advised."

The main defender of the weapons yesterday was Sen. Sam Nunn (D-Ga.), who is a member of the Armed Services Committee and has made special studies of NATO nuclear and conventional weapons.

Nunn argued that NATO would now be called upon to use nuclear weapons early in any European confrontation with the Soviets, so their destructive power would land outside allied territory. The more precise neutron weapons, which emit less blast and more radiation than regular nuclear weapons, would allow NATO more time before crossing the nuclear threshold, he argued.

After last night's vote on the Hatfield proposal, the Senate turned to an amendment by Edward M. Kennedy (D-Mass.) that would give either house of Congress a veto power should the President ultimately decide to go ahead with the neutron missile warheads and artillery shells, as he has indicated he probably will.

Also in the wings was rival proposal by Nunn and others, under which both Houses of Congress would have to veto a production decision.

Senators debated the pros and cons of the neutron weapons all day. At midday, Carter, sent up an arms control impact statement which went to the Foreign Relations Committee.

Committee members carried pieces of the statement to the floor in the afternoon, and it became the focal point of the discussion.

Sen. Charles H. Percy (R-lll.)told the Senate the "most powerful" and "most dangerous" suggestion in the impact statement was that some foreign governments might see U.S. deployment of the new type of nuclear weapons as a "doctrine change," and that this "could have an adverse effect on U.S. efforts to prevent further nuclear proliferation."

Sen. Hubert H. Humphery (D-Minn), who was among those urging Carter to send the impact statement to Capitol Hill, emphasized its conclusion that the weapons have "no arms control advantages." To the extent the neutron weapons would have any impact on ongoing negotations, "the impact would be marginally negative," he quoted the statement as saying.

Humphrey was one to call for some means whereby Congress can be assured of another shot at the issue in the future, should Carter decide to go forward.

Earlier yesterday, Humphrey had tried unsuccessfully to convince Carter he should withdraw his request for the funds until after the White House decision to go ahead with production.

Sen. Frank Church (D-Idaho) noted the impact statement said "the Soviets will continue to accuse the U.S. of contributing to the arms race in Europe," and thus, he added, "we give them a propaganda bonus with our action."

Church said he believed the neutron weapons "would bring down the existing nuclear threshhold that has for 30 years avoided a nuclear war in Europe."

Nunn challenged Church, saying the Soviets in recent years had come up, to nuclear parity in Europe, to which Church responded," "What did you expect?"

Sen. Claiborne Pell (D-R.I.) praised Carter for supplying the impact statement only hours after it had been request but added that the issues it deserved further study.

The impact statement was prepared by the National Security Council staff based on an anlysis sent to the White House in late June by the Arms Control and Disarmament Agency.

Comprehensive test ban treaty negotiations, according to the statement, "would pose limitations on further development of this class of [neutron] weapons" since "further testing would be required."

With regard to the mutual balanced forces reduction talks between NATO and the Warsaw Pact nations, the statements said deployment of Lance neutron warheads "could be cited by Soviet as evidence that the U.S. proposal would involve elimination of obsolete weapons while actual capability is being upgraded."