Here’s a list of incomes in koku per province in Japan in 1598. Bear in mind that the land surveys necessary for the assessment were completed after 8 years of peace and after Hideyoshi’s social reorganisation, so the situation during the actual Sengoku Jidai would have been different. However, the list serves as perhaps an optimum yield for each province, assuming full daimyō control over their vassals, land surveys and some improvement of infratstructure. In earlier times, some percentage of these totals could be used, and during a campaign, that percentage could rise depending on the province’s ruler increasing their control and providing infrastructural impprovements. Alternatively/additionally, the totals can be used as a way of providing a comparison between the relative wealth of provinces, all thing being equal.
Tōhoku:
Mutsu 1,672,358
Dewa 318,095
North Kantō:
Kōzuke 496,377
Shimotsuke 374,083
Hitachi 530,008
South Kantō:
Kazusa 378,892
Shimōsa 393,255
Awa 45,045
Musashi 667,126
Sagami 194,204
Kōshin’etsu:
Kai 227,616
Shinano 408,358
Echigo 390,770
Sado 17,030
Hokuriku
Etchū 380,298
Kaga 355,570
Noto 210,000
Echizen 499,411
Wakasa 85,000
Tōkai:
Izu 69,832
Suruga 150,000
Tōtōmi 255,160
Mikawa 290,750
Owari 571,737
Mino 540,000
Hida 38,000
Ise 567,105
Shima 17,854
Iga 100,000
Kinki:
Ōmi 775,379
Yamashiro 225,262
Tango 110,784
Yamato 448,946
Settsu 356,066
Kawachi 242,106
Izumi 141,513
Kii 243,550
Awaji 62,104
Harima 358,534
Tanba 263,887
Tajima 114,235
Chūgoku:
Inaba 88,500
Hōki 100,947
Izumo 186,650
Iwami 111,770
Oki 4,980
Bizen 223,762
Bitchū 176,929
Mimasaka 186,018
Bingo 186,100
Aki 194,150
Suō 167,820
Nagato 130,660
Shikoku:
Awa 183,500
Sanuki 126,200
Iyo 336,200
Tosa 98,200
Kyūshū:
Chikuzen 335,690
Chikugo 265,998
Buzen 140,000
Bungo 418,313
Hizen 309,935
Higo 341,220
TENKA FUBU 
Some figures to consider:
I’m wondering if this also provides a rough population estimate for each province. Since one koku supports one human for one year and the totals for this list= (+/-)18 million koku and with population estimates for 1600 ranging from 22m( McEvedy & Jones) to only 12m(Biraben), the figures would seem to fit. This would also correspond to around 4.5 million acres under cultivation which also supports the estimate that only 50% of arable land was given to rice cultivation and of a total estimate of 9.28 mill acres in all of Japan in the 16thC, once again the figures roughly fit.
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There’s a separate population map here, broken down into areas. So you could apply the koku totals of individual provinces within the areas to make guesses as to individual province populations. With some margin of error obviously.
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