Su Yan has already put down the matter of building a manpower plow, and completely left it to the carpenters to do, the general shape of the manpower plow is like that, and then the carpenters continue to improve it to create a suitable manpower plow.

Only wait for the new manpower plow to be built, Su Yan will take the time to come over to check, if the newly created manpower plough is applicable, it can be produced in large quantities, and it will be used in the spring ploughing next year, perhaps because of the emergence of the manpower plow, the land cultivated by the dragon tribe will increase greatly next year, and it is not far from the dragon tribe to completely enter the era of farming.

At present, Su Yan is most concerned about the cultivation of soybeans, the yield per mu of soybeans is about the same as the yield per mu of millet, but the value of soybeans is still above the corn, which involves the problem of land fertility.

One thing that many people don't know is that leguminous plants have special nodules growing on their roots, and the cause of nodules is rhizobia that live in symbiosis with leguminous plants.

Rhizobia rapidly divides and multiplies in the cortical cells of leguminous plants, and at the same time, cortical cells also divide and grow rapidly due to the stimulation of root nodule invasion, which makes the local volume of the root expand and form a nodulous protrusion, which is the root nodules.

Rhizobia takes in the water and nutrients they need to live from the rhizobia cells, and it can fix free nitrogen and synthesize nitrogen-containing compounds, which are used by legumes.

The symbiosis between leguminous plants and rhizobia yields high yields due to the acquisition of nitrogen; At the same time, due to the shedding of root nodules, the roots or stumps with root nodules are left in the soil, which can increase the fertility of the soil.

The use of leguminous plants as green manure or rotation and intercropping with other crops has a significant effect on increasing yield, simply put, leguminous plants can fertilize the field, which greatly increases the importance of soybeans to the dragon tribe.

Without fertilizer, the same farmland is cultivated every year, and soon the fertility of the farmland is quickly consumed, and the yield of crops per mu decreases year after year.

Farm fertilizer can increase the fertility of farmland to a certain extent, but it is not enough, with the addition of soybeans, nodules and farm fertilizer, the fertility of farmland continues to increase, prolong the farming life of farmland, and increase the yield of crops per mu.

If there are more types of crops in the future, and they can be rotated with other crops, the cold weather in the north cannot achieve two crops in one year, but three crops in two years can still be achieved.

Since the Blood Tiger Tribe obtained crop cultivation technology from other tribes on the south bank of the Great River, the Blood Tiger Tribe has been cultivating soybeans for nearly a hundred years.

In the past 100 years, the Blood Tiger Tribe has also been studying how to increase soybean yield, and the complex method cannot be understood, but the method of selecting high-quality seeds to increase yield has been clear, and the Blood Tiger Tribe has mastered certain techniques for soybean planting.

The people of the Blood Tiger Tribe have integrated into the Dragon Tribe, and the soybean planting technology of the Blood Tiger Tribe has also been accepted by the Dragon Tribe, coupled with Su Yan's knowledge, the Dragon Tribe has a high start for the cultivation of soybeans, which is a good start, maybe the yield per mu of soybeans will soon exceed that of millet.

The full-time farmers don't know much about the soybeans they have just planted, and they often look for new people to ask about the planting of soybeans.

……

"The ship is coming! The ship is coming! ”

Bang! Bang! Bang!

Accompanied by the shouts and gongs on the side of the "wharf", hundreds of people ran out of the construction area of the bamboo city, either pushing wheelbarrows or holding a flat pole, and gathered at the "wharf".

Due to the shallow water on the shore, the ship can not get close to the shore wharf, from the wharf to the east extends a two-zhang long wooden trestle bridge, the wooden trestle is very strong, standing on dozens of people will not cause the wooden trestle to collapse.

Soon, the big ship came, and because it was headwind, it was impossible to power the big ship with the sails that could not be turned, so it had to be rowed with oars by man.

The big boat slowly docked on the edge of the wooden trestle, and the edge of the boat was a little higher than the wooden trestle, and there were people standing on the wooden trestle, and there were people on the boat.

There was no need to give any more instructions, the people on the boat quickly moved a basket of bricks, the people on the wooden trestle took a basket of bricks and walked to the shore, a flat pole carried two baskets of bricks, a wheelbarrow carried two baskets to four baskets of bricks, and then pushed the wheelbarrow or carried the rattan basket to the construction area of the bamboo city.

The size of Bamboo Castle is about the same as that of Genjo Castle and Akagi, and it takes 600,000 to 700,000 bricks to build the walls of Bamboo Castle.

The big ship came and went to Takejo once a day, and each time it actually carried at least 3,000 bricks, plus the bricks fired by the Takejo side, Takejo rose from the ground at a faster speed than the construction of the source castle and the Akagi.

The appearance of the big ship did bring a lot of convenience to the dragon tribe, it was able to use the big ship to carry a large number of goods, and the waterway could also shorten the time to go to several cities, starting from the source city to the bamboo city in the morning, and returning to the source city in the afternoon.

The Dragons still need more ships, but there are downsides.

Originally, there was a pontoon bridge connecting the right bank and the left bank of the river in the source city, but the boats had to go back and forth between the three cities, and the pontoon bridge could only be demolished, and if you wanted to go from the right bank of the river to the left bank, you could only take a boat, but fortunately, the dragon tribe was not the only one big ship, there were also six ships built before the big ship, except for the first and smallest boat, the remaining five boats could travel on the river at will.

The other is the width of the river, the width of the big river in the south is more than two hundred zhang, and the width of the river adjacent to the dragon tribe is about twenty zhang, considering the depth of the river, this river cannot carry too many boats, nor can it carry too many boats.

Su Yan had already decided to build a new shipyard on the north or south bank of the river in the future, and to build larger ships, which would be able to carry larger ships on the river.

Many tribes live on both sides of the river or near the banks of its tributaries, and as long as the dragon tribe has the strength to cross the river, those tribes will be the target of the dragon tribe's conquest, and the cow tribe also lives near one of the tributaries of the river.

As for trading, the dragon tribe does not need to trade with other tribes, and the other tribes do not have much to trade with the dragon tribe, and even if there is, then conquer them through war.

Unless there is a unified tribe or country, war will always be the main theme of this land, and if you don't want to start a war, other tribes will drag you into it, women, food, salt, and even land are the causes of war.

The bricks were unloaded, the ship was about to return, the big sails were pulled up, and the ship slowly sailed north under the blowing of the south.